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Acta Microbiologica et Immunologica Hungarica     Full-text available via subscription   (Followers: 5)
Addiction Genetics     Open Access   (Followers: 5)
Advances in Applied Microbiology     Full-text available via subscription   (Followers: 15)
Advances in Microbiology     Open Access   (Followers: 16)
Advances in Molecular Imaging     Open Access   (Followers: 1)
African Journal of Clinical and Experimental Microbiology     Open Access  
African Journal of Microbiology Research     Open Access   (Followers: 1)
Algorithms for Molecular Biology     Open Access   (Followers: 4)
American Journal of Infectious Diseases and Microbiology     Open Access   (Followers: 16)
American Journal of Microbiological Research     Open Access   (Followers: 2)
American Journal of Microbiology     Open Access   (Followers: 13)
American Journal of Molecular Biology     Open Access   (Followers: 2)
American Journal of Stem Cell Research     Open Access   (Followers: 3)
Annals of Clinical Microbiology and Antimicrobials     Open Access   (Followers: 7)
Annals of Microbiology     Hybrid Journal   (Followers: 9)
Annual Review of Microbiology     Full-text available via subscription   (Followers: 32)
Antimicrobial Agents and Chemotherapy     Hybrid Journal   (Followers: 18)
Antiviral Research     Hybrid Journal   (Followers: 7)
Applied and Environmental Microbiology     Hybrid Journal   (Followers: 37)
Applied Biochemistry and Microbiology     Hybrid Journal   (Followers: 15)
Applied Microbiology and Biotechnology     Hybrid Journal   (Followers: 56)
Aquatic Microbial Ecology     Hybrid Journal   (Followers: 2)
Archives of Microbiology     Hybrid Journal   (Followers: 7)
Avicenna Journal of Clinical Microbiology and Infection     Open Access   (Followers: 1)
Bangladesh Journal of Medical Microbiology     Open Access  
Beneficial Microbes     Full-text available via subscription   (Followers: 1)
Bio-Research     Full-text available via subscription  
BioArchitecture     Full-text available via subscription  
Bioethanol     Open Access  
Biomaterials Science     Full-text available via subscription   (Followers: 7)
BioMolecular Concepts     Hybrid Journal   (Followers: 2)
Biomolecular Detection and Quantification     Open Access  
Biomolecules     Open Access   (Followers: 1)
Biotechnology and Molecular Biology Reviews     Open Access  
BMC Microbiology     Open Access   (Followers: 8)
Brazilian Journal of Microbiology     Open Access   (Followers: 2)
Canadian Journal of Infectious Diseases and Medical Microbiology     Open Access   (Followers: 1)
Canadian Journal of Microbiology     Full-text available via subscription   (Followers: 3)
Cell Biology : Research & Therapy     Hybrid Journal   (Followers: 2)
Cell Host & Microbe     Full-text available via subscription   (Followers: 13)
Cell Medicine     Open Access   (Followers: 3)
Cell Regeneration     Open Access   (Followers: 1)
Cell Stem Cell     Full-text available via subscription   (Followers: 29)
CellBio     Open Access  
Cells     Open Access   (Followers: 1)
Cellular & Molecular Immunology     Hybrid Journal   (Followers: 11)
Cellular and Molecular Biology Letters     Open Access   (Followers: 1)
Cellular and Molecular Life Sciences (CMLS)     Hybrid Journal   (Followers: 6)
Cellular Microbiology     Hybrid Journal   (Followers: 7)
Cheese: Chemistry, Physics and Microbiology     Full-text available via subscription   (Followers: 2)
Chimerism     Full-text available via subscription  
Clinical Microbiology and Infection     Hybrid Journal   (Followers: 16)
Clinical Microbiology Newsletter     Hybrid Journal   (Followers: 4)
Clinical Microbiology Reviews     Hybrid Journal   (Followers: 15)
Comparative Immunology, Microbiology and Infectious Diseases     Hybrid Journal   (Followers: 10)
Computational Molecular Bioscience     Open Access   (Followers: 1)
Critical Reviews in Microbiology     Hybrid Journal   (Followers: 11)
Current Clinical Microbiology Reports     Hybrid Journal   (Followers: 1)
Current Issues in Molecular Biology     Open Access   (Followers: 2)
Current Microbiology     Hybrid Journal   (Followers: 9)
Current Molecular Biology Reports     Hybrid Journal   (Followers: 1)
Current Molecular Imaging     Hybrid Journal  
Current Opinion in Microbiology     Hybrid Journal   (Followers: 28)
Current Tissue Engineering     Hybrid Journal   (Followers: 2)
Current Topics in Microbiology and Immunology     Hybrid Journal   (Followers: 6)
Diagnostic Microbiology and Infectious Disease     Hybrid Journal   (Followers: 8)
Disease and Molecular Medicine     Open Access   (Followers: 1)
DNA Barcodes     Open Access  
Egyptian Journal of Biochemistry and Molecular Biology     Full-text available via subscription  
Emerging Microbes & Infections     Open Access   (Followers: 2)
Environmental Microbiology     Hybrid Journal   (Followers: 13)
Environmental Microbiology Reports     Hybrid Journal   (Followers: 3)
Enzyme and Microbial Technology     Hybrid Journal   (Followers: 12)
Epigenetics of Degenerative Diseases     Open Access   (Followers: 4)
European Journal of Clinical Microbiology & Infectious Diseases     Hybrid Journal   (Followers: 16)
European Journal of Microbiology and Immunology     Open Access   (Followers: 8)
Experimental and Molecular Pathology     Hybrid Journal   (Followers: 4)
Experimental Cell Research     Hybrid Journal   (Followers: 6)
Fems Microbiology Ecology     Hybrid Journal   (Followers: 7)
Fems Microbiology Letters     Hybrid Journal   (Followers: 17)
Fems Microbiology Reviews     Hybrid Journal   (Followers: 21)
Fermentation     Open Access  
Folia Histochemica et Cytobiologica     Open Access  
Folia Microbiologica     Hybrid Journal   (Followers: 1)
Food Microbiology     Hybrid Journal   (Followers: 14)
Frontiers in Cell and Developmental Biology     Open Access   (Followers: 3)
Frontiers in Cellular and Infection Microbiology     Open Access   (Followers: 3)
Frontiers in Cellular Neuroscience     Open Access   (Followers: 4)
Frontiers in Microbiology     Open Access   (Followers: 8)
Frontiers in Molecular Neuroscience     Open Access   (Followers: 2)
Future Microbiology     Full-text available via subscription   (Followers: 3)
Future Virology     Full-text available via subscription   (Followers: 7)
Gene Expression     Full-text available via subscription  
Genetica si Biologie Moleculara     Open Access  
Genetics and Molecular Research     Open Access   (Followers: 4)
Geomicrobiology Journal     Hybrid Journal   (Followers: 2)
Gut Microbes     Full-text available via subscription   (Followers: 8)
IAWA Journal     Hybrid Journal  
Indian Journal of Microbiology     Hybrid Journal   (Followers: 2)
Indian Journal of Pathology and Microbiology     Open Access   (Followers: 1)
Infection Ecology & Epidemiology     Open Access   (Followers: 3)
Inside the Cell     Open Access  
International Journal of Antimicrobial Agents     Hybrid Journal   (Followers: 6)
International Journal of Bacteriology     Open Access  
International Journal of Bioassays     Open Access   (Followers: 2)
International Journal of Biotechnology and Molecular Biology Research     Open Access   (Followers: 2)
International Journal of Food Microbiology     Hybrid Journal   (Followers: 12)
International Journal of Genetics and Molecular Biology     Open Access  
International Journal of Infection and Microbiology     Open Access   (Followers: 1)
International Journal of Medical Microbiology     Hybrid Journal   (Followers: 7)
International Journal of Molecular Medicine     Full-text available via subscription   (Followers: 5)
International Journal of Mycobacteriology     Open Access  
International Journal of Systematic and Evolutionary Microbiology     Full-text available via subscription   (Followers: 3)
International Journal of Virology and Molecular Biology     Open Access  
International Microbiology     Open Access   (Followers: 3)
Invertebrate Immunity     Open Access   (Followers: 1)
JAMMI     Full-text available via subscription  
JMM Case Reports     Open Access  
Journal of Cell Science & Therapy     Open Access   (Followers: 2)
Journal of Microbial & Biochemical Technology     Open Access   (Followers: 1)
Journal of Applied Biology & Biotechnology     Open Access   (Followers: 1)
Journal of Applied Microbiology     Hybrid Journal   (Followers: 10)
Journal of Bacteriology     Hybrid Journal   (Followers: 24)
Journal of Basic Microbiology     Hybrid Journal   (Followers: 3)
Journal of Biomolecular Structure and Dynamics     Hybrid Journal   (Followers: 2)
Journal of Bionanoscience     Full-text available via subscription  
Journal of Brewing and Distilling     Open Access   (Followers: 1)
Journal of Cell and Animal Biology     Open Access  
Journal of Cell Biology and Genetics     Open Access   (Followers: 2)
Journal of Clinical Microbiology     Hybrid Journal   (Followers: 28)
Journal of Clinical Pathology     Full-text available via subscription   (Followers: 11)
Journal of Extracellular Vesicles     Open Access   (Followers: 3)
Journal of Food Microbiology     Open Access   (Followers: 3)
Journal of General and Molecular Virology     Open Access  
Journal of Genes and Cells     Open Access  
Journal of Global Antimicrobial Resistance     Hybrid Journal   (Followers: 2)
Journal of Industrial Microbiology and Biotechnology     Hybrid Journal   (Followers: 12)
Journal of Medical Microbiology     Full-text available via subscription   (Followers: 3)
Journal of Microbiological Methods     Hybrid Journal   (Followers: 1)
Journal of Microbiology     Hybrid Journal   (Followers: 7)
Journal of Microbiology and Antimicrobials     Open Access   (Followers: 2)
Journal of Microbiology Research     Open Access   (Followers: 2)
Journal of Micropalaeontology     Hybrid Journal   (Followers: 7)
Journal of Molecular Biochemistry     Open Access   (Followers: 3)
Journal of Molecular Biology Research     Open Access   (Followers: 3)
Journal of Molecular Microbiology and Biotechnology     Full-text available via subscription   (Followers: 12)
Journal of Molecular Pathophysiology     Open Access   (Followers: 1)
Journal of Molecular Psychiatry     Open Access   (Followers: 9)
Journal of Morphology     Hybrid Journal   (Followers: 2)
Journal of Pharmacy & Bioresources     Full-text available via subscription   (Followers: 3)
Journal of Plant Molecular Biology and Biotechnology     Open Access   (Followers: 7)
Journal of Plant Pathology & Microbiology     Open Access  
Journal of Proteome Science and Computational Biology     Open Access  
Journal of Regenerative Medicine and Tissue Engineering     Open Access   (Followers: 3)
Journal of The Academy of Clinical Microbiologists     Open Access  
Journal of the American Society of Brewing Chemists     Full-text available via subscription   (Followers: 2)
Journal of the Institute of Brewing     Free   (Followers: 1)
Journal of Tropical Microbiology and Biotechnology     Full-text available via subscription  
Jundishapur Journal of Microbiology     Open Access  
Letters In Applied Microbiology     Hybrid Journal   (Followers: 5)
Macrophage     Open Access  
MAP Kinase     Open Access  
Medical Mycology     Open Access   (Followers: 2)
Memórias do Instituto Oswaldo Cruz     Open Access  
Methods in Molecular Biology     Hybrid Journal   (Followers: 20)
Microbes and Health     Open Access   (Followers: 1)
Microbes and Infection     Full-text available via subscription   (Followers: 4)
Microbial Biotechnology     Open Access   (Followers: 6)
Microbial Cell Factories     Open Access   (Followers: 7)
Microbial Drug Resistance     Hybrid Journal   (Followers: 4)
Microbial Ecology     Hybrid Journal   (Followers: 6)
Microbial Ecology in Health and Disease     Open Access  
Microbial Informatics and Experimentation     Open Access   (Followers: 1)
Microbial Pathogenesis     Hybrid Journal   (Followers: 6)
Microbial Risk Analysis     Full-text available via subscription  
Microbiologia Medica     Open Access   (Followers: 1)
Microbiological Research     Hybrid Journal   (Followers: 6)
Microbiology     Hybrid Journal   (Followers: 12)
Microbiology (SGM)     Full-text available via subscription   (Followers: 16)
Microbiology and Immunology     Hybrid Journal   (Followers: 10)
Microbiology and Molecular Biology Reviews     Hybrid Journal   (Followers: 22)
Microbiology Australia     Hybrid Journal  
Microbiology Discovery     Open Access  
Microbiology Indonesia     Open Access  
Microbiology Research     Open Access   (Followers: 7)
MicrobiologyOpen     Open Access   (Followers: 2)
Microbiome     Hybrid Journal   (Followers: 2)
Microbiome Science and Medicine     Open Access  
Microorganisms     Open Access   (Followers: 2)
MicroRNA     Hybrid Journal   (Followers: 1)
Molecular and Cellular Therapies     Open Access  
Molecular Biology and Genetic Engineering     Open Access   (Followers: 1)
Molecular Biology Research Communications     Open Access   (Followers: 1)
Molecular Genetics and Metabolism Reports     Open Access   (Followers: 1)
Molecular Genetics, Microbiology and Virology     Hybrid Journal   (Followers: 6)
Molecular Imaging     Open Access  
Molecular Imaging and Biology     Hybrid Journal   (Followers: 2)
Molecular Medicine     Open Access   (Followers: 1)
Molecular Medicine Reports     Full-text available via subscription   (Followers: 6)
Molecular Microbiology     Hybrid Journal   (Followers: 25)

        1 2     

Journal Cover International Journal of Food Microbiology
  [SJR: 1.64]   [H-I: 142]   [12 followers]  Follow
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0168-1605
   Published by Elsevier Homepage  [3039 journals]
  • Microbial dynamics of indicator microorganisms on fresh tomatoes in the
           supply chain from Mexico to the USA
    • Abstract: Publication date: 5 December 2016
      Source:International Journal of Food Microbiology, Volume 238
      Author(s): Claire Zoellner, Fabiola Venegas, John J. Churey, Jorge Dávila-Aviña, Yrjo T. Grohn, Santos García, Norma Heredia, Randy W. Worobo
      Quality and safety of fresh produce are important to public health and maintaining commerce between Mexico and USA. While preventive practices can reduce risks of contamination and are generally successful, the variable environment of the supply chain of fresh produce can be suitable for introduction or proliferation of pathogenic microorganisms. As routine surveillance of these pathogens is not practical, indicator microorganisms are used to assess the sanitary conditions of production and handling environments. An opportunity exists to use indicators on fresh produce to measure how handling and transport from field to market may affect microbial populations that contribute to their quality or safety. The objective was to quantify indicator microorganisms on tomatoes sampled along the supply chain during the harvest year, in order to observe the levels and changes of populations at different locations. Roma tomatoes (n=475) were taken from the same lots (n=28) at four locations of the postharvest supply chain over five months: at arrival to and departure from the packinghouse in México, at the distribution center in Texas, and at retail in USA. Samples were analyzed individually for four microbial populations: aerobic plate count (APC), total coliforms (TC), generic Escherichia coli, and yeasts and molds (YM). APC population differed (p<0.05) from 1.9±1.1, 1.7±1.1, 2.3±1.1 and 3.5±1.4logCFU/g at postharvest, packing, distribution center and supermarket, respectively. TC populations were <1logCFU/g at postharvest, increased at packing (0.7±1.0logCFU/g), decreased in distribution (0.4±0.8logCFU/g) and increased in supermarkets (1.4±1.5logCFU/g). Generic E. coli was not identified from coliform populations in this supply chain. YM populations remained <1logCFU/g, with the exception of 1.1±1.3logCFU/g at supermarkets and tomatoes were not visibly spoiled. The levels reported from this pilot study demonstrated the dynamics within populations as influenced by time and conditions in one supply chain during a harvest year, while the large variances in some locations indicate opportunities for improvement. Overall, packinghouse and supermarket locations were identified as crucial points to control microbial safety risks.

      PubDate: 2016-09-24T18:22:35Z
  • Isolation of baker's yeast mutants with proline accumulation that showed
           enhanced tolerance to baking-associated stresses
    • Abstract: Publication date: 5 December 2016
      Source:International Journal of Food Microbiology, Volume 238
      Author(s): Ariunzaya Tsolmonbaatar, Keisuke Hashida, Yukiko Sugimoto, Daisuke Watanabe, Shuhei Furukawa, Hiroshi Takagi
      During bread-making processes, yeast cells are exposed to baking-associated stresses such as freeze-thaw, air-drying, and high-sucrose concentrations. Previously, we reported that self-cloning diploid baker's yeast strains that accumulate proline retained higher-level fermentation abilities in both frozen and sweet doughs than the wild-type strain. Although self-cloning yeasts do not have to be treated as genetically modified yeasts, the conventional methods for breeding baker's yeasts are more acceptable to consumers than the use of self-cloning yeasts. In this study, we isolated mutants resistant to the proline analogue azetidine-2-carboxylate (AZC) derived from diploid baker's yeast of Saccharomyces cerevisiae. Some of the mutants accumulated a greater amount of intracellular proline, and among them, 5 mutants showed higher cell viability than that observed in the parent wild-type strain under freezing or high-sucrose stress conditions. Two of them carried novel mutations in the PRO1 gene encoding the Pro247Ser or Glu415Lys variant of γ-glutamyl kinase (GK), which is a key enzyme in proline biosynthesis in S. cerevisiae. Interestingly, we found that these mutations resulted in AZC resistance of yeast cells and desensitization to proline feedback inhibition of GK, leading to intracellular proline accumulation. Moreover, baker's yeast cells expressing the PRO1 P247S and PRO1 E415K gene were more tolerant to freezing stress than cells expressing the wild-type PRO1 gene. The approach described here could be a practical method for the breeding of proline-accumulating baker's yeasts with higher tolerance to baking-associated stresses.

      PubDate: 2016-09-24T18:22:35Z
  • Oligosaccharides containing an α-(1→2) (glucosyl/xylosyl)-fructosyl
           linkage as inducer molecules of trichothecene biosynthesis for Fusarium
    • Abstract: Publication date: 5 December 2016
      Source:International Journal of Food Microbiology, Volume 238
      Author(s): Yuichi Nakajima, Kazuyuki Maeda, Qi Jin, Naoko Takahashi-Ando, Kyoko Kanamaru, Tetsuo Kobayashi, Makoto Kimura
      Fructo-oligosaccharides containing a sucrose unit are reported as carbon sources necessary for trichothecene production by Fusarium graminearum. Here we demonstrate that trichothecene production is induced when at least 100μM sucrose is added to a culture medium containing 333mM glucose in a 24-well plate. When glucose, the main carbon source of the medium, was replaced with galactose, maltose, or sorbitol, the addition of 100μM sucrose could no longer induce trichothecene production. However, replacing half the amount of each carbon source with glucose restored the trichothecene production-inducing activity of sucrose. Detailed investigations with media containing various concentrations of galactose and glucose as carbon sources suggested that operation of the galactose catabolic pathway for energy conservation affected trichothecene biosynthesis induction by sucrose. Trichothecene production was also induced by 100μM of either raffinose or xylosucrose in axenic liquid culture medium containing glucose as the major carbon source. These results demonstrate that sucrose derivatives are not necessary as a carbon source for inducing trichothecene biosynthesis, and that the minimum structural requirement for sugars to function as trichothecene production-inducer molecules is to contain an α-(1→2) (glucosyl/xylosyl)-fructosyl linkage.

      PubDate: 2016-09-24T18:22:35Z
  • Plasma inactivation of microorganisms on sprout seeds in a dielectric
           barrier discharge
    • Abstract: Publication date: 5 December 2016
      Source:International Journal of Food Microbiology, Volume 238
      Author(s): Denis Butscher, Hanne Van Loon, Alexandra Waskow, Philipp Rudolf von Rohr, Markus Schuppler
      Fresh produce is frequently contaminated by microorganisms, which may lead to spoilage or even pose a threat to human health. In particular sprouts are considered to be among the most risky foods sold at retail since they are grown in an environment practically ideal for growth of bacteria and usually consumed raw. Because heat treatment has a detrimental effect on the germination abilities of sprout seeds, alternative treatment technologies need to be developed for microbial inactivation purposes. In this study, non-thermal plasma decontamination of sprout seeds is evaluated as a promising option to enhance food safety while maintaining the seed germination capabilities. In detail, investigations focus on understanding the efficiency of non-thermal plasma inactivation of microorganisms as influenced by the type of microbial contamination, substrate surface properties and moisture content, as well as variations in the power input to the plasma device. To evaluate the impact of these parameters, we studied the reduction of native microbiota or artificially applied E. coli on alfalfa, onion, radish and cress seeds exposed to non-thermal plasma in an atmospheric pressure pulsed dielectric barrier discharge streamed with argon. Plasma treatment resulted in a maximum reduction of 3.4 logarithmic units for E. coli on cress seeds. A major challenge in plasma decontamination of granular food products turned out to be the complex surface topology, where the rough surface with cracks and crevices can shield microorganisms from plasma-generated reactive species, thus reducing the treatment efficiency. However, improvement of the inactivation efficiency was possible by optimizing substrate characteristics such as the moisture level and by tuning the power supply settings (voltage, frequency) to increase the production of reactive species. While the germination ability of alfalfa seeds was considerably decreased by harsh plasma treatment, enhanced germination was observed under mild conditions. In conclusion, the results from this study indicate that cold plasma treatment represents a promising technology for inactivation of bacteria on seeds used for sprout production while preserving their germination properties.

      PubDate: 2016-09-24T18:22:35Z
  • Antimicrobial effects of vinegar against norovirus and Escherichia coli in
           the traditional Korean vinegared green laver (Enteromorpha intestinalis)
           salad during refrigerated storage
    • Abstract: Publication date: 5 December 2016
      Source:International Journal of Food Microbiology, Volume 238
      Author(s): Shin Young Park, Sujin Kang, Sang-Do Ha
      In Korea, edible seaweeds are potentially regarded as high-risk foods with respect to enteric norovirus (NoV) and non-pathogenic generic Escherichia coli. This study investigated the antimicrobial effects of 5%, 10%, and 15% vinegar (6% acetic acid) on the survival of murine norovirus-1 (MNV-1), a human NoV surrogate, and E. coli, a fecal indicator in experimentally contaminated raw fresh green lavers (Enteromorpha intestinalis) during a 7-d storage period at 4°C. Both MNV-1 titers and E. coli counts significantly (p<0.05) decreased with stepwise increase in vinegar concentration and storage time, except in E. coli of the 0% vinegar-containing lavers; however, MNV-1 was more resistant to vinegar than E. coli. The overall average MNV-1 titers were significantly (p<0.05) higher in 0% vinegar-containing lavers (3.6log10PFU/ml) than in 5–15% vinegar-containing lavers (3.3–3.1log10PFU/ml) throughout the 7days of storage. A 1-log reduction in the MNV-1 titer was observed in 0% vinegar-containing laver samples after 5days of storage and 5–15% vinegar-containing laver samples after 3days of storage. The overall E. coli count was also significantly (p<0.05) decreased in the 15% (6.8log10CFU/g) vinegar-containing lavers than in the 10% (7.3log10CFU/g) and 5% (7.6log10CFU/g) vinegar-containing lavers. A >1-log reduction in the E. coli count was observed in 10–15% vinegar-containing laver samples just after 1day of storage. A 2-log reduction in the E. coli count was also observed in 10–15% vinegar-containing laver samples after 5days of storage. Using the non-linear Weibull model, this study showed that the dR-values (1-log reduction) of MNV-1 were 4.90days for 0%, 4.28days for 5%, 3.79days for 10%, and 2.88days for 15% vinegar-containing lavers, whereas those for E. coli were 1.12day for 5%, 1.03day for 10%, and 0.90day for 15% vinegar-containing lavers stored at 4°C. Vinegar with over the storage time can be used as an antimicrobial ingredient against NoV and E. coli in Korean conventional foods. Specifically, this study suggests that ~1day of storage is required for 1-log reduction in the E. coli count in the vinegar-containing (5–15%) lavers, whereas 3–5days of storage at 4°C is adequate for 1-log reduction in the MNV-1 count in the vinegar-containing and non-vinegar-containing lavers.

      PubDate: 2016-09-24T18:22:35Z
  • Inhibition of Staphylococcus aureus by antimicrobial biofilms formed by
           competitive exclusion microorganisms on stainless steel
    • Abstract: Publication date: 5 December 2016
      Source:International Journal of Food Microbiology, Volume 238
      Author(s): Hyeri Son, Sunhyung Park, Larry R. Beuchat, Hoikyung Kim, Jee-Hoon Ryu
      The goal of this study was to develop a desiccation resistant antimicrobial surface using biofilm of competitive exclusion (CE) microorganism inhibitory to Staphylococcus aureus. We isolated 161 microorganisms from soils, foods, and food-contact surfaces that are inhibitory to S. aureus. Among them, three CE microorganisms (Streptomyces spororaveus strain Gaeunsan-18, Bacillus safensis strain Chamnamu-sup 5–25, and Pseudomonas azotoformans strain Lettuce-9) exhibiting strong antibacterial activity and high growth rates were selected for evaluation. These isolates formed biofilms within 24h on stainless steel coupons (SSCs) immersed in Bennet's broth and tryptic soy broth at 25°C. Cells in these biofilms showed significantly (P ≤0.05) enhanced resistance to a desiccation (43% relative humidity [RH]) compared to those attached to SSCs but not in biofilms. The antimicrobial activities of biofilms formed by these isolates on SSCs against S. aureus at 25°C and 43% RH were determined. Compared to SSCs lacking biofilms formed by CE microorganisms, populations of S. aureus on SSCs harboring CE biofilms were significantly lower (P ≤0.05). Results indicate that persistent antimicrobial activity against S. aureus on stainless steel surfaces can be achieved by the presence of biofilms of CE microorganisms. This information will be useful when developing strategies to improve the microbiological safety of foods during storage, processing, and distribution by facilitating the development of effective antimicrobial food-contact surfaces.

      PubDate: 2016-09-20T18:18:15Z
  • Chemical, physical and morphological properties of bacterial biofilms
           affect survival of encased Campylobacter jejuni F38011 under aerobic
    • Abstract: Publication date: 5 December 2016
      Source:International Journal of Food Microbiology, Volume 238
      Author(s): Jinsong Feng, Guillaume Lamour, Rui Xue, Mehr Negar Mirvakliki, Savvas G. Hatzikiriakos, Jie Xu, Hongbin Li, Shuo Wang, Xiaonan Lu
      Campylobacter jejuni is a microaerophilic pathogen and leading cause of human gastroenteritis. The presence of C. jejuni encased in biofilms found in meat and poultry processing facilities may be the major strategy for its survival and dissemination in aerobic environment. In this study, Staphylococcus aureus, Salmonella enterica, or Pseudomonas aeruginosa was mixed with C. jejuni F38011 as a culture to form dual-species biofilms. After 4days' exposure to aerobic stress, no viable C. jejuni cells could be detected from mono-species C. jejuni biofilm. In contrast, at least 4.7logCFU/cm2 of viable C. jejuni cells existed in some dual-species biofilms. To elucidate the mechanism of protection mode, chemical, physical and morphological features of biofilms were characterized. Dual-species biofilms contained a higher level of extracellular polymeric substances with a more diversified chemical composition, especially for polysaccharides and proteins, than mono-species C. jejuni biofilm. Structure of dual-species biofilms was more compact and their surface was >8 times smoother than mono-species C. jejuni biofilm, as indicated by atomic force microscopy. Under desiccation stress, water content of dual-species biofilms decreased slowly and remained at higher levels for a longer time than mono-species C. jejuni biofilm. The surface of all biofilms was hydrophilic, but total surface energy of dual-species biofilms (ranging from 52.5 to 56.2mJ/m2) was lower than that of mono-species C. jejuni biofilm, leading to more resistance to wetting by polar liquids. This knowledge can aid in developing intervention strategies to decrease the survival and dispersal of C. jejuni into foods or environment.

      PubDate: 2016-09-20T18:18:15Z
  • The heat resistance and spoilage potential of aerobic mesophilic and
           thermophilic spore forming bacteria isolated from Chinese milk powders
    • Abstract: Publication date: 5 December 2016
      Source:International Journal of Food Microbiology, Volume 238
      Author(s): Faizan A. Sadiq, Yun Li, TongJie Liu, Steve Flint, Guohua Zhang, Lei Yuan, Zhipeng Pei, GuoQing He
      The propensity for aerobic bacilli and allied genera to produce highly heat-resistant spores and thermally stable spoilage enzymes are major bacteriological issues faced by the dairy industry. Most of the enzymes are able to survive any heat treatment applied during the manufacture of milk powders and have the potential to remain active in milk powders and other dairy products during storage, and may explain some of the sensory and functionality defects reported in dairy products. Despite many reports on the occurrence of spore-forming bacteria in dairy products, knowledge about food quality related properties of many aerobic sporeformers is still scarce. Therefore, the aim of this study was to determine thermal resistance and spoilage potential of a large pool of mesophilic and thermophilic sporeformers, representing 738 isolates and 31 different RAPD groups, recently isolated from Chinese milk powders. Spore formers producing highly heat resistant spores (surviving 125°C for 30min) included 2 thermophiles (Geobacillus thermoleovorans group and Geobacillus stearothermophilus) and one mesophilic species (Brevibacillus brevis). Paenibacillus macerans showed the highest proteolytic activity followed by members of the Bacillus cereus group, Br. brevis, Bacillus subtilis, G. thermoleovorans group and Virgibacillus proomii. The highest lipase producing strains belonged to Bacillus licheniformis. Phospholipase activity was only shown by members of the B. cereus group and Brevibacillus parabrevis. Ten strains showed positive β-galactosidase activity, while, 4 strains showed positive haemolytic activity. B. licheniformis strains, despite belonging to one RAPD group or sub-group showed markedly different phenotypic characters which support the previous findings of heterogeneity in RAPD-based B. licheniformis groups. The results of this study will broaden the knowledge about the spoilage potential and thermal resistance of many strains of dairy origin.

      PubDate: 2016-09-20T18:18:15Z
  • The efficacy of Mentha arvensis L. and M. piperita L. essential oils in
           reducing pathogenic bacteria and maintaining quality characteristics in
           cashew, guava, mango, and pineapple juices
    • Abstract: Publication date: 5 December 2016
      Source:International Journal of Food Microbiology, Volume 238
      Author(s): Jossana Pereira de Sousa Guedes, José Alberto da Costa Medeiros, Richard Sidney de Souza e Silva, Janaína Maria Batista de Sousa, Maria Lúcia da Conceição, Evandro Leite de Souza
      This study evaluated the ability of the essential oil from Mentha arvensis L. (MAEO) and M. piperita L. (MPEO) to induce ≥5-log reductions in counts (CFU/mL) of E. coli, L. monocytogenes, and Salmonella enterica serovar Enteritidis in Brain-Heart Infusion broth (BHIB) and cashew, guava, mango, and pineapple juices during refrigerated storage (4±0.5°C). The effects of the incorporation of these essential oils on some physicochemical and sensory parameters of juices were also evaluated. The incorporation of 5, 2.5, 1.25, or 0.625μL/mL of MAEO in BHIB caused a ≥5-log reduction in counts of E. coli and Salmonella Enteritidis after 24h of storage; but only 5μL/mL was able to cause the same reduction in counts of L. monocytogenes. The incorporation of 10μL/mL of MPEO in BHIB caused a ≥5-log reduction in counts of E. coli, Salmonella Enteritidis, and L. monocytogenes after 24h of storage; smaller reductions were observed in BHIB containing 5, 2.5, and 1.25μL/mL of MPEO. Similar reductions were observed when the MAEO or MPEO was incorporated at the same concentrations in mango juice. The incorporation of MAEO or MPEO at all tested concentrations in cashew, guava, and pineapple juices resulted in a ≥5-log reduction in pathogen counts within 1h. The incorporation of MAEO and MPEO (0.625 and 1.25μL/mL, respectively) in fruit juices did not induce alterations in °Brix, pH, and acidity, but negatively affected the taste, aftertaste, and overall acceptance. The use of MAEO or MPEO at low concentrations could constitute an interesting tool to achieve the required 5-log reduction of pathogenic bacteria in cashew, guava, mango, and pineapple fruit juices. However, new methods combining the use of MAEO or MPEO with other technologies are necessary to reduce their negative impacts on specific sensory properties of these juices.

      PubDate: 2016-09-20T18:18:15Z
  • LaeA and VeA are involved in growth morphology, asexual development, and
           mycotoxin production in Alternaria alternata
    • Abstract: Publication date: 5 December 2016
      Source:International Journal of Food Microbiology, Volume 238
      Author(s): N. Estiarte, C.B. Lawrence, V. Sanchis, A.J. Ramos, A. Crespo-Sempere
      Alternaria alternata is a common filamentous fungus that contaminates various fruits, grains and vegetables causing important economic losses to farmers and the food industry. A. alternata is a mycotoxigenic mould, which may jeopardize human and animal health. Two of the most common A. alternata mycotoxins found in food and feed are alternariol and alternariol monomethyl ether. In this study we examined the role of LaeA and VeA, two regulatory proteins belonging to the velvet family, which have been described to be involved in several functions in many fungi including secondary metabolism. We found that deletion of laeA and veA genes, respectively, greatly reduced sporulation and strongly compromised mycotoxin production, both in vitro or during pathogenesis of tomato fruits. We have also studied how the loss of laeA and veA may affect expression of genes related to alternariol and alternariol monomethyl ether biosynthesis (pksJ and altR), and to melanin biosynthesis (cmrA, pksA).

      PubDate: 2016-09-20T18:18:15Z
  • Fermentation of African kale (Brassica carinata) using L. plantarum BFE
           5092 and L. fermentum BFE 6620 starter strains
    • Abstract: Publication date: 5 December 2016
      Source:International Journal of Food Microbiology, Volume 238
      Author(s): Folarin A. Oguntoyinbo, Gyu-Sung Cho, Bernhard Trierweiler, Jan Kabisch, Niels Rösch, Horst Neve, Wilhelm Bockelmann, Lara Frommherz, Dennis S. Nielsen, Lukasz Krych, Charles M.A.P. Franz
      Vegetables produced in Africa are sources of much needed micronutrients and fermentation is one way to enhance the shelf life of these perishable products. To prevent post-harvest losses and preserve African leafy vegetables, Lactobacillus plantarum BFE 5092 and Lactobacillus fermentum BFE 6620 starter strains were investigated for their application in fermentation of African kale (Brassica carinata) leaves. They were inoculated at 1×107 cfu/ml and grew to a maximum level of 108 cfu/ml during 24h submerged fermentation. The strains utilized simple sugars (i.e., glucose, fructose, and sucrose) in the kale to quickly reduce the pH from pH6.0 to pH3.6 within 24h. The strains continued to produce both d and l lactic acid up to 144h, reaching a maximum concentration of 4.0g/l. Fermentations with pathogens inoculated at 104 cfu/ml showed that the quick growth of the starters inhibited the growth of Listeria monocytogenes and Salmonella Enteritidis, as well as other enterobacteria. Denaturing gradient gel electrophoresis and 16S rRNA gene (V3-V4-region) amplicon sequencing showed that in the spontaneous fermentations a microbial succession took place, though with marked differences in biodiversity from fermentation to fermentation. The fermentations inoculated with starters however were clearly dominated by both the inoculated strains throughout the fermentations. RAPD-PCR fingerprinting showed that the strains established themselves at approx. equal proportions. Although vitamins C, B1 and B2 decreased during the fermentation, the final level of vitamin C in the product was an appreciable concentration of 35mg/100g. In conclusion, controlled fermentation of kale offers a promising avenue to prevent spoilage and improve the shelf life and safety.

      PubDate: 2016-09-11T11:00:56Z
  • Comparative proteomic analyses for elucidating metabolic changes during
           EPS production under different fermentation temperatures by Lactobacillus
           plantarum Q823
    • Abstract: Publication date: 5 December 2016
      Source:International Journal of Food Microbiology, Volume 238
      Author(s): Esteban Vera Pingitore, Alessandro Pessione, Cecilia Fontana, Roberto Mazzoli, Enrica Pessione
      Exopolysaccharide (EPS)-producing bacteria are of growing interest in industrial processes, mainly concerning food. Lactic acid bacteria are widely appreciated for their GRAS (generally recognized as safe) status and their ascertained or putative probiotic features. Detailed investigation on what happens at metabolic level during EPS production is scarce in the literature. The facultative heterofermenter Lactobacillus plantarum Q823 was studied in order to compare growth and EPS production at 30°C and 37°C. A higher growth rate was observed at 37°C, whereas, a significantly higher (tenfold increase) EPS amount was produced at 30°C. To understand the molecular mechanisms leading to the different EPS production in the two conditions, a comparative proteomic experiment was performed. The results of the in-gel proteomics revealed that: i) at 37°C a higher abundance of proteins involved in carbon catabolism and nucleic acid biosynthesis together with a significant amount of stress proteins was observed; ii) at 30°C the production of an atypical manganese-containing non-heme catalase (pseudocatalase) was increased, in agreement with previous data reporting that growth-rates of catalase negative Lactobacillus plantarum strains were greater than that of catalase positive strains. Taken together, all these findings provide further insights about the metabolic pathways stimulated during EPS production, and the mechanism that triggers EPS biosynthesis.

      PubDate: 2016-09-11T11:00:56Z
  • Virulence factors and antimicrobial resistance in Escherichia coli strains
           isolated from hen egg shells
    • Abstract: Publication date: 5 December 2016
      Source:International Journal of Food Microbiology, Volume 238
      Author(s): María José Grande Burgos, Maria Luisa Fernández Márquez, Rubén Pérez Pulido, Antonio Gálvez, Rosario Lucas López
      Eggs may contain extraintestinal pathogenic (ExPEC) and diarrheogenic (DEC) Escherichia coli which in addition may carry antibiotic resistance. The wide use of biocides and disinfectants in the food industry may induce biocide tolerance in bacteria. The aim of the present study was to evaluate biocide tolerance and antibiotic resistance in E. coli from hen egg shells. A total of 27 isolates obtained from a screening of 180 eggs were studied. Seven isolates carried both eae and bfpA genes of typical enteropathogenic E. coli (EPEC) strains, while 14 isolates only carried eae associated with atypical EPEC strains. Shiga toxin genes stx and stx2 were detected in four isolates. Heat-stable and heat-labile enterotoxin genes as well as aggR were also detected. Several isolates had minimum inhibitory concentrations (MICs) that were higher than the wild-type for the biocide hexadecylpyridinium chloride (HDP, 18.52%) or the commercial disinfectant P3 oxonia (OX, 14.81%). Antibiotic resistance was detected for ampicillin (37.03%), streptomycin (37.03%), tetracycline (37.03%), chloramphenicol (11.11%), nalidixic acid (18.51%) and trimethoprim-sulfamethoxazole (14.81%). Eight isolates (29.63%) were biocide tolerant and antibiotic resistant. Efflux pump genes detected included acrB (96.29%), mdfA (85.18%) and oxqA (37.03%), in addition to quaternary ammonium compound (QAC) resistance genes qacA/B (11.11%) and qacE (7.40%). Antibiotic resistance genes detected included bla CTX-M-2 (22.22%), bla TEM (3.70%), bla PSE (3.70%), tet(A) (29.63%), tet(B) (29.63%), tet(C) (7.40%), tet(E) (11.11%), aac(6′)-Ib (3.70%), sul1 (14.81%), dfrA12 (3.70%) and dfrA15 (3.70%). Most isolates (96.30%) carried more than one genetic determinant of resistance. The most frequent combinations were efflux pump components acrB and mdfA with tetracycline resistance genes (33.33% of isolates). Isolates carrying QAC resistance genes also carried between 4 and 8 of the additional antimicrobial resistance genes investigated. Regardless of biocide tolerance and antibiotic resistance, all isolates were sensitive to carvacrol (0.25%), thymol (0.125%) and trisodium phosphate (1 to 1.5%), but they exhibited a heterogeneous response to sodium lactate and lysozyme-EDTA combinations that apparently were not related with antibiotic resistance. Results from the study reveal not only a low incidence of biocide tolerance but also the presence of multiple resistance strains carrying multiple genetic determinants of resistance.

      PubDate: 2016-09-11T11:00:56Z
  • Is staphylococci population from milk of healthy goats safe'
    • Abstract: Publication date: 5 December 2016
      Source:International Journal of Food Microbiology, Volume 238
      Author(s): Patricia Ruiz, Iris Barragán, Susana Seseña, María Llanos Palop
      The aim of this study was to assess the species and the genetic diversity of the staphylococci population in raw milk from healthy goats. Isolates representative of all genotypes were screened for their potential pathogenicity by the occurrence of some relevant safety-related properties, such as antibiotic resistance, presence of virulence factor genes, biofilm formation ability and biogenic amine production. A total of 314 staphylococci were isolated, and randomly amplified polymorphic DNA-PCR analysis displayed 48 genotypes. Isolates were identified as belonging to S. epidermidis (87.5%), S. caprae (6.2%), S. aureus (4.2%) and S. simulans (2.1%) species. The antibiotic resistance varied strongly with strains, with S. epidermidis and S. aureus strains showing resistance to more number of antibiotics. A high occurrence of strains harbouring hemolysin genes was also found in both species. On the contrary, none of the strains assayed harboured enterotoxin or amino acid decarboxylase genes, and, although a moderate or high biofilm formation was observed in 29% of the strains, they did not harbour icaA or icaD genes. This study gives a first and extensive picture of safety-related properties within Staphylococcus species isolated from milk of healthy goats, displaying that these species can act as a reservoir for spreading genes related to safety.

      PubDate: 2016-09-11T11:00:56Z
  • Effect of sodium alginate coating incorporated with nisin, Cinnamomum
           zeylanicum, and rosemary essential oils on microbial quality of chicken
           meat and fate of Listeria monocytogenes during refrigeration
    • Abstract: Publication date: 5 December 2016
      Source:International Journal of Food Microbiology, Volume 238
      Author(s): Mojtaba Raeisi, Alijan Tabaraei, Mohammad Hashemi, Nasser Behnampour
      The present study was conducted to preserve the microbial quality of chicken meat fillets during storage time by using sodium alginate active coating solutions incorporated with different natural antimicrobials including nisin, Cinnamomum zeylanicum (cinnamon), and rosemary essential oils (EOs) which were added individually and in combination. The samples were stored in refrigeration condition for 15days and were analyzed for total viable count, Enterobacteriaceae count, lactic acid bacteria count, Pseudomonas spp. count, psychrotrophic count, and yeast and mold count, as well as fate of inoculated Listeria monocytogenes at 3-day intervals. Results indicated that values of tested microbial indicators in all samples increased during storage. Antimicrobial agents, when used in combination, had stronger effect in preserving the microbial quality of chicken meat samples rather than their individual use and the strongest effect was observed in samples coated with alginate solution containing both cinnamon and rosemary EOs (CEO+REO). However, all treatments significantly inhibited microbial growth when compared to the control (P <0.05). Therefore, based on the results of this study, application of alginate coating solutions containing nisin, cinnamon, and rosemary EOs as natural preservatives is recommended in meat products especially in chicken meats.

      PubDate: 2016-09-11T11:00:56Z
  • Distribution of tannin-'tolerant yeasts isolated from Miang, a traditional
    • Abstract: Publication date: 5 December 2016
      Source:International Journal of Food Microbiology, Volume 238
      Author(s): Apinun Kanpiengjai, Naradorn Chui-Chai, Siriporn Chaikaew, Chartchai Khanongnuch
      Miang is a fermented food product prepared from the tea leaves of Camellia sinensis var. assamica, and is traditionally produced in mountainous areas of northern Thailand. Although Miang has a long history and reveals deep-rooted cultural involvement with local people in northern Thailand, little is known regarding its microbial diversity. Yeasts were isolated from 47 Miang samples collected from 28 sampling sites, including eight provinces in upper northern Thailand. A hundred and seven yeast isolates were recovered and identified within 14 species based on the comparison of the D1/D2 sequence of the large subunit (LSU) rRNA gene. Candida ethanolica was determined to be the dominant species that was frequently found in Miang together with minor resident yeast species. All yeast isolates demonstrated their tannin-tolerant capability when cultivated on yeast malt agar (YMA) containing 50g/l tannin, but nine isolates displayed clear zones forming around their colonies, e.g., Debaryomyces hansenii, Cyberlindnera rhodanensis, and Sporidiobolus ruineniae. The results obtained from a visual reading method of tannase revealed that all yeast isolates were positive for methyl gallate, indicating that they possess tannase activity. It is assumed that a tannin-tolerant ability is one of the most important factors for developing a yeast community in Miang. This research study is the first report to describe tannin-tolerant yeasts and yeast communities in traditionally fermented tea leaves.

      PubDate: 2016-09-11T11:00:56Z
  • Characteristics of Vibrio parahaemolyticus isolates obtained from crayfish
           (Procambarus clarkii) in freshwater
    • Abstract: Publication date: 5 December 2016
      Source:International Journal of Food Microbiology, Volume 238
      Author(s): Xingxing Dong, Zhi Li, Xiaohong Wang, Min Zhou, Li Lin, Yang Zhou, Jinquan Li
      Vibrio parahaemolyticus usually occurs in coastal areas and is generally recognized as a marine bacterium. It has become the leading cause of gastroenteritis worldwide. In the present study, 96 V. parahaemolyticus isolates were obtained from freshwater crayfish (Procambarus clarkii) and classified by multilocus sequence typing. Fifty-three sequence types (STs) were identified among the 96 isolates analyzed, 38 of which were novel STs. These isolates fell into six groups and 42 singletons, suggesting a high level of genetic diversity. Screening for 9 virulence and virulence-related genes in the isolates revealed that 40 isolates contained more than two genes with possible roles in pathogenicity. The virulence of the representative isolates VP66 (trh +, ureC +, T3SS1+, T3SS2β+, T6SS2+) and VP80 (T3SS1+, T6SS1+, T6SS2+) were further assessed in zebrafish and mouse infection model in vivo, and the tested isolates were shown to be lethal to both zebrafish and mice. These results suggest that crayfish may serve as a carrier of V. parahaemolyticus in freshwater, and that some isolates may have the potential to cause foodborne disease in humans.

      PubDate: 2016-09-11T11:00:56Z
  • Staphylococci isolated from ready-to-eat meat – Identification,
           antibiotic resistance and toxin gene profile
    • Abstract: Publication date: 5 December 2016
      Source:International Journal of Food Microbiology, Volume 238
      Author(s): Karol Fijałkowski, Dorota Peitler, Jolanta Karakulska
      The aim of this study was to analyse the staphylococci isolated from ready-to-eat meat products, including pork ham, chicken cold cuts, pork sausage, salami and pork luncheon meat, sliced in the store to the consumer's specifications, along with species identification and determination of antibiotic resistance. Genes encoding staphylococcal enterotoxins, staphylococcal enterotoxin-like proteins, exfoliative toxins, and toxic shock syndrome toxin 1 were also investigated. From the 41 samples, 75 different staphylococcal isolates were obtained. Based on PCR-RFLP analysis of the gap gene using AluI and HpyCH4V restriction enzymes, the isolates were identified as Staphylococcus equorum (28%), S. vitulinus (16%), S. carnosus (14%), S. succinus (11%), S. xylosus (11%), S. saprophyticus (9%), S. warneri (9%), S. haemolyticus (1%) and S. pasteuri (1%). The incidence and number of resistances to antimicrobials was found to be species but not source of isolation dependent. All S. xylosus, S. saprophyticus, S. haemolyticus and S. pasteuri isolates showed antibiotic resistance. A lower percentage of resistance was recorded for S. warneri (71%) and S. vitulinus (58%), followed by S. equorum (57%), S. carnosus (50%) and S. succinus (50%). The most frequent resistance was observed to fusidic acid (43%). The mecA gene was amplified in 4% of the staphylococci. However, phenotypic resistance to methicillin was not confirmed in any of these isolates. On the other hand, the mecA gene was not detected in any of 9% of the isolates resistant to cefoxitin. It was also found that among 75 isolates, 60 (80%) harbored from 1 to 10 out of 21 analyzed superantigenic toxin genes. The most prevalent genes were: sei (36% isolates) among enterotoxins, seln (32% isolates) among enterotoxin-like proteins and eta encoding exfoliative toxin A (37% isolates). The findings of this study further extend previous observations that, when present in food, not only S. aureus but also other species of staphylococci could be of public health significance.

      PubDate: 2016-09-11T11:00:56Z
  • Extended-spectrum β-lactamase producing Enterobacteriaceae in bulk tank
           milk from German dairy farms
    • Abstract: Publication date: 5 December 2016
      Source:International Journal of Food Microbiology, Volume 238
      Author(s): Sabrina Odenthal, Ömer Akineden, Ewald Usleber
      Although the dairy farm environment is a known source of extended-spectrum β-lactamase (ESBL)-producing bacteria, surveillance data on ESBL in the milk production chain are still scarce. This study aimed at estimating the dimensions of the problem for public health and animal welfare by surveying ESBL-producing Enterobacteriaceae in raw bulk tank milk in Germany. Samples from 866 dairy farms, comprising about 1% of the total number of dairy farms in Germany, were first screened for presence of cefotaxime-resistant bacteria by selective enrichment. Suspect colonies were identified phenotypically and further characterized by biochemical and molecular methods, including analysis of resistance genes and clonal diversity in ESBL-producing isolates. Bulk tank milk from 82 (9.5%) farms yielded Enterobacteriaceae with confirmed ESBL-production. The most frequent ESBL-producing species was Escherichia coli (75.6%), followed by Citrobacter spp. (9.6%), Enterobacter cloacae (6.1%), and Klebsiella oxytoca (3.7%), a few isolates belonged to other species within the genera Hafnia, Raoutella and Serratia. The majority of isolates (95.1%) harbored the β-lactamase blaCTX-M gene, which has gained increased importance among ESBL-producing strains worldwide; the CTX-M group 1 was found to be the dominating (88.4%) phylogenetic group. All ESBL-positive Escherichia coli isolates were clonally heterogeneous, as determined by pulsed-field gel electrophoresis. The results from this survey demonstrate that ESBL-producing bacteria are distributed widely in the dairy farm environment in Germany. Therefore, raw milk is a potential source of exposure for the consumer, which is of increasing importance considering the trend of farmer-to-consumer direct marketing. Furthermore, dairy farm staff have an increased likelihood of exposure to ESBL-producing bacteria. Finally, ESBL-producing bacteria may also be transferred via waste milk to calves, thus further spreading antibiotic resistance in the farm environment.

      PubDate: 2016-09-05T10:57:08Z
  • Biofilm formation, phenotypic production of cellulose and gene expression
           in Salmonella enterica decrease under anaerobic conditions
    • Abstract: Publication date: 5 December 2016
      Source:International Journal of Food Microbiology, Volume 238
      Author(s): A. Lamas, J.M. Miranda, B. Vázquez, A. Cepeda, C.M. Franco
      Salmonella enterica subsp. enterica is one of the main food-borne pathogens. This microorganism combines an aerobic life outside the host with an anaerobic life within the host. One of the main concerns related to S. enterica is biofilm formation and cellulose production. In this study, biofilm formation, morphotype, cellulose production and transcription of biofilm and quorum sensing-related genes of 11 S. enterica strains were tested under three different conditions: aerobiosis, microaerobiosis, and anaerobiosis. The results showed an influence of oxygen levels on biofilm production. Biofilm formation was significantly higher (P<0.05) in aerobiosis than in microaerobiosis and anaerobiosis. Cellulose production and RDAR (red, dry, and rough) were expressed only in aerobiosis. In microaerobiosis, the strains expressed the SAW (smooth and white) morphotype, while in anaerobiosis the colonies appeared small and red. The expression of genes involved in cellulose synthesis (csgD and adrA) and quorum sensing (sdiA and luxS) was reduced in microaerobiosis and anaerobiosis in all S. enterica strains tested. This gene expression levels were less reduced in S. Typhimurium and S. Enteritidis compared to the tested serotypes. There was a relationship between the expression of biofilm and quorum sensing-related genes. Thus, the results from this study indicate that biofilm formation and cellulose production are highly influenced by atmospheric conditions. This must be taken into account as contamination with these bacteria can occur during food processing under vacuum or modified atmospheres.

      PubDate: 2016-09-05T10:57:08Z
  • Variability of Listeria monocytogenes strains in biofilm formation on
           stainless steel and polystyrene materials and resistance to peracetic acid
           and quaternary ammonium compounds
    • Abstract: Publication date: 21 November 2016
      Source:International Journal of Food Microbiology, Volume 237
      Author(s): Sofia V. Poimenidou, Marilena Chrysadakou, Aikaterini Tzakoniati, Vasiliki C. Bikouli, George-John Nychas, Panagiotis N. Skandamis
      Listeria monocytogenes is a foodborne pathogen able to tolerate adverse conditions by forming biofilms or by deploying stress resistant mechanisms, and thus manages to survive for long periods in food processing plants. This study sought to investigate the correlation between biofilm forming ability, tolerance to disinfectants and cell surface characteristics of twelve L. monocytogenes strains. The following attributes were evaluated: (i) biofilm formation by crystal violet staining method on polystyrene, and by standard cell enumeration on stainless steel and polystyrene; (ii) hydrophobicity assay using solvents; (iii) minimum inhibitory concentration (MIC) and biofilm eradication concentration (BEC) of peracetic acid (PAA) and quaternary ammonium compounds (QACs), and (iv) resistance to sanitizers (PAA 2000ppm; QACs 500ppm) of biofilms on polystyrene and stainless steel. After 72h of incubation, higher biofilm levels were formed in TSB at 20°C, followed by TSB at 37°C (P =0.087) and diluted TSB 1/10 at both 20 (P =0.005) and 37°C (P =0.004). Cells grown at 30°C to the stationary phase had significant electron donating nature and a low hydrophobicity, while no significant correlation of cell surface properties to biofilm formation was observed. Strains differed in MICPAA and BECPAA by 24- and 15-fold, respectively, while a positive correlation between MICPAA and BECPAA was observed (P =0.02). The MICQACs was positively correlated with the biofilm-forming ability on stainless steel (P =0.03). Regarding the impact of surface type, higher biofilm populations were enumerated on polystyrene than on stainless steel, which were also more tolerant to disinfectants. Among all strains, the greatest biofilm producer was a persistent strain with significant tolerance to QACs. These results may contribute to better understanding of L. monocytogenes behavior and survival on food processing surfaces.

      PubDate: 2016-09-05T10:57:08Z
  • Survival of foodborne pathogens (Escherichia coli O157:H7, Salmonella
           Typhimurium, Staphylococcus aureus, Listeria monocytogenes, and Vibrio
           parahaemolyticus) in raw ready-to-eat crab marinated in soy sauce
    • Abstract: Publication date: 5 December 2016
      Source:International Journal of Food Microbiology, Volume 238
      Author(s): T.J. Cho, N.H. Kim, S.A. Kim, J.H. Song, M.S. Rhee
      Knowing the survival characteristics of foodborne pathogens in raw ready-to-eat (RTE) seafood is the key to predicting whether they pose a microbiological hazard. The present study examined the survival of Escherichia coli O157:H7, Salmonella Typhimurium, Vibrio parahaemoliticus, Listeria monocytogenes, and Staphylococcus aureus in raw RTE crab marinated in soy sauce. Inoculated crabs (initial bacterial population=4.1–4.4logCFU/g) were immersed in soy sauce and then stored at refrigeration (5°C) or room temperature (22°C) for up to 28days. At 5°C, all bacteria (except V. parahaemolyticus) survived in crab samples until Day 28 (counts of 1.4, 1.6, 3.1, 3.2 log CFU/g for E. coli O157:H7, S. Typhimurium, L. monocytogenes, and S. aureus, respectively). However, at 22°C, all tested bacteria were more susceptible to the antimicrobial effects of marination. Regardless of temperature, foodborne pathogens attached to crab samples were more resistant to marination than those suspended in soy sauce samples; however, the survival pattern for each species was different. Gram-positive bacteria were most resistant to marination conditions (high salinity, low pH), whereas V. parahaemolyticus was extremely susceptible. Marination is the only antibacterial step in the manufacturing processes; however, the results presented herein reveal that this is not sufficient to inactivate foodborne pathogens. In particular, the survival of pathogens on crabs at refrigeration temperature may pose a major hazard for the consumption of raw RTE seafood. Thus, appropriate decontamination methods and implementation of safety management practices are needed. This study provides predictive microbiological information of foodborne pathogens in raw RTE seafood with marination.

      PubDate: 2016-09-05T10:57:08Z
  • Characterization of a plasmid carrying cat, ermB and tetS genes in a
           foodborne Listeria monocytogenes strain and uptake of the plasmid by
           cariogenic Streptococcus mutans
    • Abstract: Publication date: 5 December 2016
      Source:International Journal of Food Microbiology, Volume 238
      Author(s): Lili Li, Rikke Heidemann Olsen, Lei Shi, Lei Ye, Jianhua He, Hecheng Meng
      A multi-drug resistant (MDR) Listeria monocytogenes isolate (serotype 1/2c) was recovered from a quick-frozen rice flour product collected from Langfang city in northern China. PCR screening identified the presence of cat, ermB and tetS genes. The plasmid profile of the strain showed the presence of an approximately 22.4-kb plasmid. Curing of this plasmid resulted in the loss of cat, ermB and tetS genes and increased susceptibility to several antibiotics, suggesting the involvement of the plasmid in multiple antibiotic resistances. Moreover, the plasmid was able to be uptaken by human oral pathogen Streptococcus mutans by natural transformation and resulted in the acquiring of multiple resistances in the transconjugants. This study contributes to our knowledge on acquired multi-drug resistance in foodborne pathogenic L. monocytogenes, which will add to a better understanding of effective clinical management of listeriosis.

      PubDate: 2016-09-05T10:57:08Z
  • Comparative morphological characteristics of three Brettanomyces
           bruxellensis wine strains in the presence/absence of sulfur dioxide
    • Abstract: Publication date: 5 December 2016
      Source:International Journal of Food Microbiology, Volume 238
      Author(s): Marli Louw, Maret du Toit, Hervé Alexandre, Benoit Divol
      The red wine spoilage yeast Brettanomyces bruxellensis has been the subject of numerous investigations. Some of these studies focused on spoilage mechanisms, sulfur dioxide tolerance and nutrient requirements. Pseudomycelium formation, although a striking feature of this species, has however been poorly investigated. Furthermore, literature regarding the induction mechanism of pseudomycelium formation in this yeast is limited and lacks clarity, as results published are contradictory. This study elucidates this phenomenon among strains from geographically different areas. Potential environmental cues were investigated, to attain a better understanding of this mechanism and its role as a survival strategy. SO2 was previously reported to induce this morphological change however results obtained in this study did not support this. Nevertheless, the results obtained using scanning and transmission electron microscopy illustrate, for the first time in this yeast, deformity to the cell membrane and alterations to the fibrillar layers in SO2 treated cells. In addition, the SO2 exposed cultures displayed cell size variations, with cells displaying a decrease in length as well as delayed growth, with a prolonged lag phase. Fluorescence microscopy demonstrated a decrease in metabolic activity and the appearance of inclusion body-like structures in the cells following exposure to SO2.

      PubDate: 2016-09-05T10:57:08Z
  • Polymorphism and phylogenetic species delimitation in filamentous fungi
           from predominant mycobiota in withered grapes
    • Abstract: Publication date: 5 December 2016
      Source:International Journal of Food Microbiology, Volume 238
      Author(s): M. Lorenzini, M.S. Cappello, A. Logrieco, G. Zapparoli
      Filamentous fungi are the main pathogens of withered grapes destined for passito wine production. Knowledge of which species inhabit these post-harvest fruits and their pathogenicity is essential in order to develop strategies to control infection, but is still scarce. This study investigated the predominant mycobiota of withered grapes through a cultivation-dependent approach. Strain and species heterogeneity was evidenced on examining isolates collected over three consecutive years. Colony morphology and PCR-restriction fragment length polymorphism (PCR-RFLP) analysis revealed the occurrence of several phenotypes and haplotypes, respectively. Strains were phylogenetically analyzed based on sequence typing of different genes or regions (e.g. calmodulin, β-tubulin and internal transcribed spacer region). Beside the most common necrotrophic-saprophytic species of Penicillium, Aspergillus, Alternaria and Botrytis species responsible for fruit rot, other saprobic species were identified (e.g. Trichoderma atroviride, Sarocladium terricola, Arthrinium arundinis and Diaporthe eres) generally not associated with post-harvest fruit diseases. Species such as Penicillium ubiquetum, Cladosporium pseudocladosporioides, Lichtheimia ramosa, Sarocladium terricola, Diaporthe nobilis, Bipolaris secalis, Paraconiothyrium fuckelii and Galactomyces reessii that had never previously been isolated from grapevine or grape were also identified. Moreover, it was not possible to assign a species to some isolates, while some members of Didymosphaeriaceae and Didymellaceae remained unclassified even at genus level. This study provides insights into the diversity of the epiphytic fungi inhabiting withered grapes and evidences the importance of their identification to understand the causes of fruit diseases. Finally, phylogenetic species delimitation furnished data of interest to fungal taxonomy.

      PubDate: 2016-09-05T10:57:08Z
  • Assessment of table olive fermentation by functional data analysis
    • Abstract: Publication date: 5 December 2016
      Source:International Journal of Food Microbiology, Volume 238
      Author(s): M.A. Ruiz-Bellido, V. Romero-Gil, P. García-García, F. Rodríguez-Gómez, F.N. Arroyo-López, A. Garrido-Fernández
      For the first time, functional data analysis (FDA) was used to assess the effects of different treatments on Protection Denomination of Origin Aloreña de Málaga table olive fermentations, focusing on the evolution of yeast population. The analysis of fermentation by a conventional approach led to scarce information. However, the transformation of microbial (and also physicochemical) data into smooth curves allowed the application of a new battery of statistical tools for the analysis of fermentations (functional pointwise estimation of the averages and standard deviations, maximum, minimum, first and second derivatives, functional regression, and functional F and t-tests). FDA showed that all the treatments assayed led to similar trends in yeast population while changes in pH and titratable acidity profiles led to several significant differences. Therefore, FDA represents a promising and valuable tool for studying table olive fermentations and for food microbiology in general.

      PubDate: 2016-08-31T14:03:07Z
  • Development of synthetic media mimicking food soils to study the behaviour
           of Listeria monocytogenes on stainless steel surfaces
    • Abstract: Publication date: 5 December 2016
      Source:International Journal of Food Microbiology, Volume 238
      Author(s): Anaïs Overney, Danielle Chassaing, Brigitte Carpentier, Laurent Guillier, Olivier Firmesse
      Listeria monocytogenes is one of the main targets of hygiene procedures in the ready-to-eat food industry due to its ability to persist for months or even years in processing plants, where it can contaminate food during processing. The factors associated with persistence are often those that foster growth, which itself depends on food contamination of surfaces. It is therefore essential to experiment by using food soils or media modelling these soils to understand the behaviour of L. monocytogenes on surfaces of food processing plants. Thus, we set up an experimental plan including three physiological parameters characteristic of the behaviour of cells on surfaces, namely spatial distribution, adhesion forces and the physiological state of sessile L. monocytogenes. These were recorded in two food soils: smoked salmon juice and meat exudate. According to our results, the behaviour of L. monocytogenes on stainless steel surfaces is highly dependent on the food soil used. The presence of viable but non-culturable (VBNC) cells was demonstrated using meat exudate, while all viable cells were recovered using smoked salmon juice. Moreover, on the basis of our criteria and after validation with three strains of L. monocytogenes, we showed that smoked salmon juice can be substituted by a modified culture medium, demonstrating that drawbacks associated with the use of food soils can be overcome.

      PubDate: 2016-08-31T14:03:07Z
  • Antifungal properties of fermentates and their potential to replace
           sorbate and propionate in pound cake
    • Abstract: Publication date: 21 November 2016
      Source:International Journal of Food Microbiology, Volume 237
      Author(s): S. Samapundo, F. Devlieghere, A. Vroman, M. Eeckhout
      The major objective of this study was to assess the antifungal activities of commercially available ‘clean label’ fermentates and their potential to replace the preservative function of sorbate and propionate in cake. This study was performed in two parts. In the first part of the study the inhibitory activities of selected fermentates - FA, FB, FC and FD - towards Aspergillus tritici and Aspergillus amstelodami were assessed as a function of pH (5.0–6.5) on malt extract agar (MEA). In the second part of the study, challenge, shelf-life and sensorial tests were used to determine the suitability of these fermentates to replace potassium sorbate and calcium propionate in quarter pound cake. All the fermentates evaluated in this study all had significant (p <0.05) inhibitory activities towards A. tritici and A. amstelodami within the recommended dosage range for application in bakery products. In all cases, the inhibitory activity of the fermentates increased with a decrease in the pH and an increase in concentration. FC was generally the most inhibitory whilst FD was the least inhibitory. Significant (p <0.05) synergistic interactions were determined to occur between the effects of pH and concentration for all fermentates evaluated in this study. The sensorial tests with FC showed that cakes produced with ≤1% FC (on basis of the batter) did not differ significantly (p >0.05) in flavour from the reference cake (0.5% calcium propionate and 0.54% potassium sorbate). However, the challenge and shelf-life tests showed that cakes produced with ≤1% FC were not as microbiologically shelf-stable as the reference cake, especially when sliced. Therefore, it can be concluded that whilst fermentates have appreciable antifungal effects, their use could potentially result in reduced shelf-stabilities. Robust challenge and shelf-life tests would be recommended before the marketing of cakes were propionate and/or sorbate has been replaced to ensure accurate shelf-lives are stated.

      PubDate: 2016-08-31T14:03:07Z
  • Minimal processing of iceberg lettuce has no substantial influence on the
           survival, attachment and internalization of E. coli O157 and Salmonella
    • Abstract: Publication date: 5 December 2016
      Source:International Journal of Food Microbiology, Volume 238
      Author(s): Inge Van der Linden, Karina R. Avalos Llano, Markus Eriksson, Winnok H. De Vos, Els J.M. Van Damme, Mieke Uyttendaele, Frank Devlieghere
      The influence of a selection of minimal processing techniques (sanitizing wash prior to packaging, modified atmosphere, storage conditions under light or in the dark) was investigated in relation to the survival of, attachment to and internalization of enteric pathogens in fresh produce. Cut Iceberg lettuce was chosen as a model for fresh produce, Escherichia coli O157:H7 (E. coli O157) and Salmonella enterica were chosen as pathogen models. Care was taken to simulate industrial post-harvest processing. A total of 50±0.1g of fresh-cut Iceberg lettuce was packed in bags under near ambient atmospheric air with approximately 21% O2 (NAA) conditions or equilibrium modified atmosphere with 3% O2 (EMAP). Two lettuce pieces inoculated with E. coli O157 BRMSID 188 or Salmonella Typhimurium labeled with green fluorescent protein (GFP) were added to each package. The bags with cut lettuce were stored under either dark or light conditions for 2days at 7°C. The pathogens' capacity to attach to the lettuce surface and cut edge was evaluated 2days after inoculation using conventional plating technique and the internalization of the bacteria was investigated and quantified using confocal microscopy. The effect of a sanitizing wash step (40mg/L NaClO or 40mg/L peracetic acid+1143mg/L lactic acid) of the cut lettuce prior to packaging was evaluated as well. Our results indicate that both pathogens behaved similarly under the investigated conditions. Pathogen growth was not observed, nor was there any substantial influence of the investigated atmospheric conditions or light/dark storage conditions on their attachment/internalization. The pathogens attached to and internalized via cut edges and wounds, from which they were able to penetrate into the parenchyma. Internalization through the stomata into the parenchyma was not observed, although some bacteria were found in the substomatal cavity. Washing the cut edges with sanitizing agents to reduce enteric pathogen numbers was not more effective than a rinse with precooled tap water prior to packaging. Our results confirm that cut surfaces are the main risk for postharvest attachment and internalization of E. coli O157 and Salmonella during minimal processing and that storage and packaging conditions have no important effect.

      PubDate: 2016-08-31T14:03:07Z
  • Culture-dependent and independent techniques to monitor yeast species
           during cold soak carried out at different temperatures in winemaking
    • Abstract: Publication date: 21 November 2016
      Source:International Journal of Food Microbiology, Volume 237
      Author(s): Y. Paola Maturano, M. Victoria Mestre, Mariana Combina, María Eugenia Toro, Fabio Vazquez, Braulio Esteve-Zarzoso
      Transformation of grape must into wine is a process that may vary according to the consumers' requirements. Application of cold soak prior to alcoholic fermentation is a common practice in cellars in order to enhance flavor complexity and extraction of phenolic compounds. However, the effect of this step on wine yeast microbiota is not well-known. The current study simultaneously analyzed the effect of different cold soak temperatures on the microbiological population throughout the process and the use of culture-dependent and independent techniques to study this yeast ecology. The temperatures assayed were those normally applied in wineries: 2.5, 8 and 12°C. PCR-DGGE allowed detection of the most representative species such as Hanseniaspora uvarum, Starmerella bacillaris and Saccharomyces cerevisiae. As could be expected, highest diversity indices were obtained at the beginning of each process, and survival of H. uvarum or S. bacillaris depended on the temperature. Our results are in agreement with those obtained with culture independent methods, but qPCR showed higher precision and a different behavior was observed for each yeast species and at each temperature assayed. Comparison of both culture-independent techniques can provide a general overview of the whole process, although DGGE does not reveal the diversity expected due to the reported problems with the sensitivity of this technique.

      PubDate: 2016-08-31T14:03:07Z
  • In vitro activity of plant extracts against biofilm-producing food-related
    • Abstract: Publication date: 5 December 2016
      Source:International Journal of Food Microbiology, Volume 238
      Author(s): Antonia Nostro, Alessandra Guerrini, Andreana Marino, Massimo Tacchini, Mara Di Giulio, Alessandro Grandini, Methap Akin, Luigina Cellini, Giuseppe Bisignano, Hatice T. Saraçoğlu
      The identification of effective antimicrobial agents also active on biofilms is a topic of crucial importance in food and industrial environment. For that purpose methanol extracts of Turkish plants, Ficus carica L., Juglans regia L., Olea europaea L., Punica granatum L. and Rhus coriaria L., were investigated. Among the extracts, P. granatum L. and R. coriaria L. showed the best antibacterial activity with minimum inhibitory concentrations (MIC) of 78–625μg/ml for Listeria monocytogenes and Staphylococcus aureus and 312–1250μg/ml for Escherichia coli and Pseudomonas aeruginosa. SubMICs produced a significant biofilm inhibition equal to 80–60% for L. monocytogenes and 90–80% for S. aureus. The extracts showed also the highest polyphenol content and the strongest antioxidant activity. Bioassay-guided and HPLC procedures demonstrated the presence of apigenin 4′-O-β-glucoside in P. granatum L. and myricetrin and quercitrin in R. coriaria L. Antigenotoxicity of plant extracts was also observed The present findings promote the value-adding of P. granatum L. and R. coriaria L. leaves as natural antimicrobial/antioxidant agents for control of food-related bacterial biofilms.

      PubDate: 2016-08-31T14:03:07Z
  • Inhibition of mycotoxin-producing fungi by Bacillus strains isolated from
           fish intestines
    • Abstract: Publication date: 5 December 2016
      Source:International Journal of Food Microbiology, Volume 238
      Author(s): Flávio Fonseca Veras, Ana Paula Folmer Correa, Juliane Elisa Welke, Adriano Brandelli
      Bacillus strains isolated from the aquatic environment of the Brazilian Amazon region were tested for their activity against mycotoxigenic fungi. All tested bacteria showed antifungal activity, inhibiting at least 7 indicator fungi. Four Bacillus strains showing promising antifungal results were subsequently evaluated for their activity in reducing mycelial growth rate, sporulation, spore germination percentage, and mycotoxin production. Bacillus sp. P1 and Bacillus sp. P11 had a remarkable antifungal effect on toxigenic fungi. Washed bacterial cell suspension of strains P1 and P11 (107 CFU/ml) reduced by >70% the fungal colony diameters, including a complete inhibition of ochratoxin A (OTA) producing Aspergillus spp. Significant reduction of growth rate, sporulation and spore germination were also observed. The bacteria influenced the production of mycotoxins, causing a reduction around 99 and 97% in AFB1 and OTA concentration, respectively. Chromatographic analysis revealed the presence of lipopeptides (iturin A and surfactin isomers) in butanol extracts of cell-free supernatants and cell pellets of strains P1 and P11. Furthermore, antifungal activity of these extracts was confirmed against A. flavus A12 and A. carbonarius ITAL293, producers of AFB1 and OTA, respectively. These bacterial strains could be promising biocontrol agents against toxigenic fungi.

      PubDate: 2016-08-31T14:03:07Z
  • Fungal strains and the development of tolerance against natamycin
    • Abstract: Publication date: 5 December 2016
      Source:International Journal of Food Microbiology, Volume 238
      Author(s): Hugo Streekstra, Alex E.E. Verkennis, Robbert Jacobs, Angelina Dekker, Jacques Stark, Jan Dijksterhuis
      Antimicrobial resistance is a relevant theme with respect to both antibacterial and antifungal compounds. In this study we address the possible development of tolerance against the antifungal food preservative natamycin. A selection of 20 fungal species, originating from a medical as well as a food product context, was subjected to increasing concentrations of natamycin for prolonged time, a procedure designated as “training”. The range of Minimum Inhibitory Concentrations (M.I.C.) before (1.8–19.2μM) and after (1.8–19.8μM) training did not change significantly, but natamycin-exposure caused an increase of M.I.C. in 13 out of 20 tested strains. The average M.I.C. increased from 6.1 to 8.6μM and 4 strains showed a >2-fold increase of tolerance after training. One strain (of Aspergillus ochraceus) also showed increased tolerance to amphotericin B and nystatin. However, two Fusarium strains showed similar or even decreased tolerance for these other polyene antifungals. The work reported here shows that a continuous and prolonged increasing selection pressure induced natamycin tolerance in individual strains. This implies that such a selection pressure should be avoided in the technical application of natamycin to ensure its continued safe use as a food preservative.

      PubDate: 2016-08-31T14:03:07Z
  • Sanitizing radish seeds by simultaneous treatments with gaseous chlorine
           dioxide, high relative humidity, and mild heat
    • Abstract: Publication date: 21 November 2016
      Source:International Journal of Food Microbiology, Volume 237
      Author(s): Jihyun Bang, Moonhak Choi, Hyeri Son, Larry R. Beuchat, Yoonsook Kim, Hoikyung Kim, Jee-Hoon Ryu
      Sanitizing radish seeds intended for edible sprout production was achieved by applying simultaneous treatments with gaseous chlorine dioxide (ClO2), high relative humidity (RH, 100%), and mild heat (55°C). Gaseous ClO2 was produced from aqueous ClO2 (0.66ml) by mixing sulfuric acid (5% w/v) with sodium chlorite (10 mg/mL) in a sealed container (1.8L). Greater amounts of gaseous ClO2 were measured at 23% RH (144ppm after 6h) than at 100% RH (66ppm after 6h); however, the lethal activity of gaseous ClO2 against naturally occurring mesophilic aerobic bacteria (MAB) on radish seeds was significantly enhanced at 100% RH. For example, when exposed to gaseous ClO2 at 23% RH, the number of MAB on radish seeds decreased from 3.7logCFU/g to 2.6logCFU/g after 6h. However, when exposed to gaseous ClO2 at 100% RH for 6h, the MAB population decreased to 0.7logCFU/g after 6h. Gaseous ClO2 was produced in higher amounts at 55°C than at 25°C, but decreased more rapidly over time at 55°C than at 25°C. The lethal activity of gaseous ClO2 against MAB on radish seeds was greater at 55°C than at 25°C. When radish seeds were treated with gaseous ClO2 (peak concentration: 195ppm) at 100% RH and 55°C, MAB were reduced to populations below the detectable level (<−0.7logCFU/g) within 2h without decreasing the seed germination rate (97.7%). The lethality of combined treatments against artificially inoculated Escherichia coli O157:H7 was also evaluated. When exposed to gaseous ClO2 at 100% RH and 55°C for 6h, the initial number of E. coli O157:H7 (3.5logCFU/g) on radish seeds decreased to below the detection limit (0.7logCFU/g) by direct plating but it was not eliminated from seeds. The germination rate of radish seeds was not significantly (P> 0.05) decreased after treatment for 6h. The information reported here will be useful when developing decontamination strategies for producing microbiologically safe radish seed sprouts.

      PubDate: 2016-08-27T14:00:08Z
  • Development of IgY based sandwich ELISA for the detection of
           staphylococcal enterotoxin G (SEG), an egc toxin
    • Abstract: Publication date: 21 November 2016
      Source:International Journal of Food Microbiology, Volume 237
      Author(s): Sowmya Nagaraj, Shylaja Ramlal, Joseph Kingston, Harsh Vardhan Batra
      Staphylococcal food poisoning (SFP) is a major foodborne illness caused by staphylococcal enterotoxins (SEs). It is a well known fact that foodborne outbreak investigations are solely characterized by commercially available immunoassay kits. However, these assays encompass only few enterotoxins such as SEA-SEE which are renowned as “classical” enterotoxins and unable to detect any other novel enterotoxins even though their involvement is predicted. In this context, the present study involved development of a sandwich ELISA immunoassay for the specific detection of “non-classical” enterotoxin G (SEG). The toxin belongs to enterotoxin gene cluster (egc) which comprises a bunch of five toxin genes that are known to co-express. Thus, the developed assay might indirectly speculate the presence of other toxins in the cluster. The efficiency of ELISA was compared with PCR analysis where all strains possessing seg were found positive for toxin production. Additionally, analogous to other studies which reported the co-occurrence of seg and sei, the PCR analysis accomplished in the study evinced the same. The sandwich format allowed sensitive detection with a detection limit of 1ng/mL. High specificity was achieved in presence of non-target protein as well as bacteria. Likewise, staphylococcal protein A (SpA) interference that is inevitably associated with immunoassays was eliminated by implementation of anti-SEG IgY in our study. Consequently, chicken IgY were used to capture target antigen in developed sandwich ELISA. Further, spiking studies and analysis on natural samples emphasized the robustness as well as applicability of developed method. Altogether, the established assay could be a reliable detection tool for the routine investigation of SEG as well as to predict other egc toxins in samples from food and clinical sources.

      PubDate: 2016-08-27T14:00:08Z
  • Bioactive extracts from berry byproducts on the pathogenicity of
           Salmonella Typhimurium
    • Abstract: Publication date: 21 November 2016
      Source:International Journal of Food Microbiology, Volume 237
      Author(s): Serajus Salaheen, Ekta Jaiswal, Jungsoo Joo, Mengfei Peng, Ryan Ho, Danielle OConnor, Katrina Adlerz, Jose Helim Aranda-Espinoza, Debabrata Biswas
      The aim of this study was to evaluate the phenotypic and genotypic properties of Salmonella enterica serovar Typhimurium (ST) in the presence of lethal and sublethal concentrations (SLC2LOG) of blackberry (Rubus fruticosus) and blueberry (Vaccinium corymbosum) pomace extracts. Antimicrobial susceptibility, physicochemical properties, motility, biofilm formation ability, virulence gene expression patterns, and the ability of ST to colonize in chick cecum were evaluated in the presence of these bioactive extracts. HPLC-MS analysis indicated that the phenolics in the berry pomace extracts consisted, but not limited to, flavan, flavanone, flavones, glucuronides, glucosides, quinolones, catechol, coumarin, phenols, luteolines, tannins, quercetin, chlorogenic acid, ellagic acid, gallic acid, and xanthoxic acid. The SLC2LOG of both berry pomace extracts increased the rates of injured ST by ~50%; significantly decreased the hydrophobicity, auto-aggregation, cellular motility, and invasion into cultured INT407, HD11, and DF1 cells. The relative expression of type III secretion system regulated genes, hilA, hilC, invA, invF, sirA, and sirB was significantly downregulated in ST. In addition, natural colonization ability of Salmonella in chick cecum was reduced by more than two logs in the presence of 0.5 and 1.0gGallicAcidEquivalent/L berry pomace extracts when provided as water supplement. Findings from this study reveal the high potential of phenolic extracts from berry pomaces as a green antimicrobial against enteric pathogen Salmonella and application in the reduction of pre-harvest colonization level of Salmonella in poultry gut.

      PubDate: 2016-08-27T14:00:08Z
  • Campylobacters and their bacteriophages from chicken liver: The prospect
           for phage biocontrol
    • Abstract: Publication date: 21 November 2016
      Source:International Journal of Food Microbiology, Volume 237
      Author(s): Antung S. Firlieyanti, Phillippa L. Connerton, Ian F. Connerton
      Consumption of foods containing chicken liver has been associated with Campylobacter enteritis. Campylobacters can contaminate the surface of livers post-mortem but can also arise through systemic infection of colonising bacteria in live birds. The use of bacteriophage to reduce levels of Campylobacter entering the food chain is a promising intervention approach but most phages have been isolated from chicken excreta. This study examined the incidence and contamination levels of Campylobacter and their bacteriophage in UK retail chicken liver. Using enrichment procedures, 87% of 109 chicken livers were surface contaminated with Campylobacter and 83% contaminated within internal tissues. Direct plating on selective agar allowed enumeration of viable bacteria from 43% of liver samples with counts ranging from 1.8–>3.8log10 CFU/cm2 for surface samples, and 3.0–>3.8log10 CFU/g for internal tissue samples. Three C. jejuni isolates recovered from internal liver tissues were assessed for their ability to colonise the intestines and extra-intestinal organs of broiler chickens following oral infection. All isolates efficiently colonised the chicken intestines but were variable in their abilities to colonise extra-intestinal organs. One isolate, CLB104, could be recovered by enrichment from the livers and kidneys of three of seven chickens. Campylobacter isolates remained viable within fresh livers stored at 4°C over 72h and frozen livers stored at −20°C over 7days in atmospheric oxygen, and therefore constitute a risk to human health. Only three Campylobacter-specific bacteriophages were isolated, and these exhibited a limited host range against the Camplylobacter chicken liver isolates. All were identified as group III virulent bacteriophage based on their genome size of 140kb. The application of broad host range group II virulent phages (8log10 PFU/g) to liver homogenates containing C. jejuni strains of diverse origin at 4°C resulted in modest but significant reductions in the viable counts ranging from 0.2 to 0.7log10 CFU/g.

      PubDate: 2016-08-27T14:00:08Z
  • Dielectric barrier discharge atmospheric cold plasma inhibits Escherichia
           coli O157:H7, Salmonella, Listeria monocytogenes, and Tulane virus in
           Romaine lettuce
    • Abstract: Publication date: 21 November 2016
      Source:International Journal of Food Microbiology, Volume 237
      Author(s): Sea C. Min, Si Hyeon Roh, Brendan A. Niemira, Joseph E. Sites, Glenn Boyd, Alison Lacombe
      The present study investigated the effects of dielectric barrier discharge atmospheric cold plasma (DACP) treatment on the inactivation of Escherichia coli O157:H7, Salmonella, Listeria monocytogenes, and Tulane virus (TV) on Romaine lettuce, assessing the influences of moisture vaporization, modified atmospheric packaging (MAP), and post-treatment storage on the inactivation of these pathogens. Romaine lettuce was inoculated with E. coli O157:H7, Salmonella, L. monocytogenes (~6logCFU/g lettuce), or TV (~2logPFU/g lettuce) and packaged in either a Petri dish (diameter: 150mm, height: 15mm) or a Nylon/polyethylene pouch (152×254mm) with and without moisture vaporization. Additionally, a subset of pouch-packaged leaves was flushed with O2 at 5% or 10% (balance N2). All of the packaged lettuce samples were treated with DACP at 34.8kV for 5min and then analyzed either immediately or following post-treatment storage for 24h at 4°C to assess the inhibition of microorganisms. DACP treatment inhibited E. coli O157:H7, Salmonella, L. monocytogenes, and TV by 1.1±0.4, 0.4±0.3, 1.0±0.5logCFU/g, and 1.3±0.1logPFU/g, respectively, without environmental modifications of moisture or gas in the packages. The inhibition of the bacteria was not significantly affected by packaging type or moisture vaporization (p >0.05) but a reduced-oxygen MAP gas composition attenuated the inhibition rates of E. coli O157:H7 and TV. L. monocytogenes continued to decline by an additional 0.6logCFU/g in post-treatment cold storage for 24h. Additionally, both rigid and flexible conventional plastic packages appear to be suitable for the in-package decontamination of lettuce with DACP.

      PubDate: 2016-08-27T14:00:08Z
  • Activity of R(+) limonene on the maximum growth rate of fish spoilage
           organisms and related effects on shelf-life prolongation of fresh gilthead
           sea bream fillets
    • Abstract: Publication date: 21 November 2016
      Source:International Journal of Food Microbiology, Volume 237
      Author(s): Filippo Giarratana, Daniele Muscolino, Chiara Beninati, Graziella Ziino, Alessandro Giuffrida, Antonio Panebianco
      R(+)limonene (LMN) is the major aromatic compound in essential oils obtained from oranges, grapefruits, and lemons. The improvement of preservation techniques to reduce the growth and activity of spoilage microorganisms in foods is crucial to increase their shelf life and to reduce the losses due to spoilage. The aim of this work is to evaluate the effect of LMN on the shelf life of fish fillets. Its effectiveness was preliminarily investigated in vitro against 60 strains of Specific Spoilage Organisms (SSOs) and then on gilt-head sea bream fillets stored at 2±0.5°C for 15days under vacuum. LMN showed a good inhibitory effect against tested SSOs strains. On gilt-head sea bream fillets, LMN inhibited the growth SSOs effectively, and its use resulted in a shelf-life extension of ca. 6–9days of treated fillets, compared to the control samples. The LMN addition in Sparus aurata fillets giving a distinctive smell and like-lemon taste to fish fillets that resulted pleasant to panellists. Its use contributed to a considerable reduction of fish spoilage given that the fillets treated with LMN were still sensory acceptable after 15days of storage. LMN may be used as an effective antimicrobial system to reduce the microbial growth and to improve the shelf life of fresh gilt-head sea bream fillets.

      PubDate: 2016-08-22T13:54:07Z
  • Contamination of salmon fillets and processing plants with spoilage
    • Abstract: Publication date: 21 November 2016
      Source:International Journal of Food Microbiology, Volume 237
      Author(s): Trond Møretrø, Birgitte Moen, Even Heir, Anlaug Å. Hansen, Solveig Langsrud
      The processing environment of salmon processing plants represents a potential major source of bacteria causing spoilage of fresh salmon. In this study, we have identified major contamination routes of important spoilage associated species within the genera Pseudomonas, Shewanella and Photobacterium in pre-rigor processing of salmon. Bacterial counts and culture-independent 16S rRNA gene analysis on salmon fillet from seven processing plants showed higher levels of Pseudomonas spp. and Shewanella spp. in industrially processed fillets compared to salmon processed under strict hygienic conditions. Higher levels of Pseudomonas spp. and Shewanella spp. were found on fillets produced early on the production day compared to later processed fillets. The levels of Photobacterium spp. were not dependent on the processing method or time of processing. In follow-up studies of two plants, bacterial isolates (n =2101) from the in-plant processing environments (sanitized equipment/machines and seawater) and from salmon collected at different sites in the production were identified by partial 16S rRNA gene sequencing. Pseudomonas spp. dominated in equipment/machines after sanitation with 72 and 91% of samples from the two plants being Pseudomonas-positive. The phylogenetic analyses, based on partial 16S rRNA gene sequencing, showed 48 unique sequence profiles of Pseudomonas of which two were dominant. Only six profiles were found on both machines and in fillets in both plants. Shewanella spp. were found on machines after sanitation in the slaughter department while Photobacterium spp. were not detected after sanitation in any parts of the plants. Shewanella spp. and Photobacterium spp. were found on salmon in the slaughter departments. Shewanella was frequently present in seawater tanks used for bleeding/short term storage. In conclusion, this study provides new knowledge on the processing environment as a source of contamination of salmon fillets with Pseudomonas spp. and Shewanella spp., while Photobacterium spp. most likely originate from the live fish and seawater. The study show that strict hygiene during processing is a prerequisite for optimal shelf life of salmon fillets and that about 90% reductions in the initial levels of bacteria on salmon fillets can be obtained using optimal hygienic conditions.

      PubDate: 2016-08-22T13:54:07Z
  • Microbial degradation of aflatoxin B1: Current status and future advances
    • Abstract: Publication date: 21 November 2016
      Source:International Journal of Food Microbiology, Volume 237
      Author(s): C. Verheecke, T. Liboz, F. Mathieu
      Aflatoxin B1 (AFB1) is a natural toxin produced by many food-contaminant fungi and is a threat to human and animal health. This review summarizes current knowledge of the different ways to limit AFB1 in the food chain. We start by introducing current data and reviews available on the prevention of AFB1 occurrence, on AFB1 non-biological decontamination and biological adsorption. We then focus on microbial AFB1-degradation. The latter has already been well studied using living organisms, supernatants or purified enzymes. This review compiles information on the variety of protocols and the efficacy of the different sub-kingdoms or classes of microorganisms or their enzymes. We pay particular attention to publications closest to in vivo applications of microbial AFB1-degradation. In addition, this review also provides a summary of the currently known microbial degradation metabolites of AFB1 and their levels of toxicity, and provides recommendations on the most promising techniques to pursue the aim of minimizing ABF1 in the food supply.

      PubDate: 2016-08-18T16:22:00Z
  • Microbiological and molecular characterization of commercially available
           probiotics containing Bacillus clausii from India and Pakistan
    • Abstract: Publication date: 21 November 2016
      Source:International Journal of Food Microbiology, Volume 237
      Author(s): Vania Patrone, Paola Molinari, Lorenzo Morelli
      Probiotics are actively used for treatment of diarrhoea, respiratory infections, and prevention of infectious gastrointestinal diseases. The efficacy of probiotics is due to strain-specific features and the number of viable cells; however, several reports of deviations from the label in the actual content of strains in probiotic products are a matter of concern. Most of the available data on quality focuses on probiotic products containing lactobacilli and/or bifidobacteria, while very few data are available on spore-forming probiotics. The present study evaluates the label claims for spore count and species identification in five commercial probiotic products marketed in India and Pakistan that claim to contain Bacillus clausii: Tufpro, Ecogro, Enterogermina, Entromax, and Ospor. Bacterial enumeration from three batches was done by microbiological plating methods by two independent operators. Species identification was done using PCR amplification and sequence analysis of the 16S rRNA gene, and determination of the total amount of species present in the products was done using PCR-denaturing gradient gel electrophoresis (PCR-DGGE) analysis followed by DNA sequencing of the excised bands. Plate count methods demonstrated poor correlations between quantitative label indications and bacteria recovered from plates for Tufpro, Ecogro, and Ospor. The 16S rRNA analysis performed on bacteria isolated from plate counts showed that only Enterogermina and Ospor contained homogenous B. clausii. PCR-DGGE analysis revealed that only Enterogermina had a homogenous B. clausii population while other products had mixed bacterial populations. In conclusion, the current analysis clearly demonstrates that of the five analysed commercial probiotics, only Enterogermina followed the label claims.

      PubDate: 2016-08-18T16:22:00Z
  • Mould and mycotoxin exposure assessment of melon and bush mango seeds, two
           common soup thickeners consumed in Nigeria
    • Abstract: Publication date: 21 November 2016
      Source:International Journal of Food Microbiology, Volume 237
      Author(s): Chibundu N. Ezekiel, Michael Sulyok, Yinka Somorin, Foluke I. Odutayo, Stella U. Nwabekee, Afeez T. Balogun, Rudolf Krska
      An examination of the mould and fungal metabolite pattern in melon and bush mango seeds locally produced in Nigeria was undertaken in order to understand the mycotoxicological risk posed to consumers of both of these important and commonly consumed soup thickeners. The variation in mycotoxin levels in graded categories of both foodstuffs were also determined. Aspergillus, Fusarium, Penicillium, Mucorales and Trichoderma were the recovered fungi from the foodstuffs with Aspergillus species dominating (melon=97.8%; bush mango=89.9%). Among the Aspergillus species identified Aspergillus section Flavi dominated (melon: 72%; bush mango: 57%) and A. flavus, A. parasiticus, A. parvisclerotigenus and A. tamarii were the recovered species. About 56% and 73% of the A. flavus isolates from melon and bush mango seed samples, respectively were aflatoxigenic. Thirty-four and 59 metabolites including notable mycotoxins were found in the melon and bush mango seeds respectively. Mean aflatoxin levels (μg/kg) in melon (aflatoxin B1 (AFB1)=37.5 and total aflatoxins=142) and bush mango seeds (AFB1 =68.1 and total aflatoxins=61.7) were higher than other mycotoxins, suggesting potential higher exposure for consumer populations. Significantly (p <0.05) higher levels of mycotoxins were found in hand-peeled melon and discoloured bush mango seeds than in machine-peeled melon and non-discoloured seeds except for HT-2 and T-2 toxins which occurred conversely. All melon and bush mango seeds exceeded the 2μg/kg AFB1 limit whereas all melon and 55% of bush mango seeds exceeded the 4μg/kg total aflatoxin EU limit adopted in Nigeria. This is the first report of (1) mycotoxin co-occurrence in bush mango seeds, (2) cyclopiazonic acid, HT-2 toxin, moniliformin, mycophenolic acid, T-2 toxin and tenuazonic acid occurrence, and (3) mycotoxin exposure assessment of both foodstuffs.

      PubDate: 2016-08-18T16:22:00Z
  • Morin inhibits biofilm production and reduces the virulence of Listeria
           monocytogenes — An in vitro and in vivo approach
    • Abstract: Publication date: 21 November 2016
      Source:International Journal of Food Microbiology, Volume 237
      Author(s): Murugesan Sivaranjani, Shanmugaraj Gowrishankar, Arumugam Kamaladevi, Shunmugiah Karutha Pandian, Kirshnaswamy Balamurugan, Arumugam Veera Ravi
      The current study explores the in vitro and in vivo antibiofilm efficacy of morin against a leading foodborne pathogen-Listeria monocytogenes (LM). Minimum inhibitory concentration (MIC) of morin against LM strains was found to be 100μg/ml. The non-antibacterial effect of morin at its sub-MICs (6.25, 12.5 and 25μg/ml) was determined through growth curve and XTT assay. Morin at its sub-MICs demonstrated a significant dose dependent inhibitory efficacy against LM biofilm formation which was also evidenced through light, confocal and scanning electron microscopic analyses. However, morin failed to disperse the mature biofilm of LM even at its MIC. Our data also revealed the anti-virulence efficacy of morin, as it significantly inhibited the production of hemolysin and motility of LM. Concentration-dependent susceptibility of morin treated LM cells to normal human serum was observed. In vivo studies revealed that morin extended the lifespan of LM infected Caenorhabditis elegans by about 85%. Furthermore, the non-toxic nature and in vivo anti-adherence efficacy of morin were also ascertained through C. elegans-LM infection model. Overall, the data of the current study identifies morin as a promising antibiofilm agent and its suitability to formulate protective strategies against biofilm associated infections caused by LM.

      PubDate: 2016-08-18T16:22:00Z
  • The four-component aureocin A70 as a promising agent for food
    • Abstract: Publication date: 21 November 2016
      Source:International Journal of Food Microbiology, Volume 237
      Author(s): Patrícia Carlin Fagundes, Felipe Miceli de Farias, Olinda Cabral da Silva Santos, Juliana Aparecida Souza da Paz, Hilana Ceotto-Vigoder, Daniela Sales Alviano, Maria Teresa Villela Romanos, Maria do Carmo de Freire Bastos
      Aureocin A70 is the only four-component bacteriocin described to date. As it inhibits the growth of a wide range of Gram-positive bacteria, including Listeria monocytogenes strains isolated from food, its potential for improving food safety was investigated in this study. Aureocin A70 (10,240AU/mL) proved to be bactericidal, but not extensively lytic, against listerial strains. The antibacterial activity of aureocin A70 (16AU/mL) was then tested in UHT-treated skimmed milk inoculated with the food-associated L. monocytogenes L12 strain (4-log CFU/mL) during storage at 4°C for one week. Aureocin A70 caused a time-dependent reduction in the listerial viable cell counts (5.51-log units) up to 7days of incubation. Aureocin A70 was neither toxic to the Vero and the L-929 cell lines nor exhibited a hemolytic activity against sheep red blood cells. Aureocin A70 proved to be completely stable for one month at 25°C, 16weeks at 4°C and 20weeks at −20°C. Aureocin A70 exhibited a time-dependent susceptibility to simulated gastric juice and bile salts mimicking gastrointestinal conditions. The entrapment of aureocin A70 in an alginate/gelatin matrix revealed that this bacteriocin can be released from this matrix. Moreover, it remained adsorbed to and active on a low-density polyethylene plastic surface suggesting that aureocin A70 may be employed in bioactive packaging to control the growth of undesirable bacteria. Taken together these results suggest that aureocin A70 is a promising alternative to be used in food applications.

      PubDate: 2016-08-18T16:22:00Z
  • Occurrence of Coxiella burnetii in goat and ewe unpasteurized cheeses:
           Screening and genotyping
    • Abstract: Publication date: 21 November 2016
      Source:International Journal of Food Microbiology, Volume 237
      Author(s): Alessia Galiero, Filippo Fratini, Cesare Cammà, Marco Di Domenico, Valentina Curini, Irene Baronti, Barbara Turchi, Domenico Cerri
      Q fever is a zoonosis caused by Coxiella burnetii which infects humans as well as several animal species; sheep, goats and cattle are the primary animal reservoir. The main route of human exposure to Coxiella burnetii is inhalation of contaminated aerosols from excreta, especially birth products, while the role of unpasteurized dairy products in the transmission of Q fever to humans remains still controversial. The aim of this work was to evaluate the presence of Coxiella burnetii in unpasteurized cheese samples (n=84) by PCR and to genotype the circulating strains by Multispacer sequence typing (MST) analysis. Coxiella burnetii DNA was detected in 27/84 (32.14%) cheeses and positivity rate of handicraft cheeses reached 17.24%, while positivity rate of non-handicraft cheeses reached 65.38%. In addition, the MST profile of Coxiella burnetii detected in 5 cheese samples have shown the circulation of ST12 and ST32 genotypes in Tuscany.

      PubDate: 2016-08-18T16:22:00Z
  • Unconventional bacterial association for dough leavening
    • Abstract: Publication date: 21 November 2016
      Source:International Journal of Food Microbiology, Volume 237
      Author(s): Alida Musatti, Chiara Mapelli, Roberto Foschino, Claudia Picozzi, Manuela Rollini
      The purpose of the research was to obtain innovative yeast-free doughs leavened by Zymomonas mobilis and Lactobacillus sanfranciscensis. Z. mobilis, as well as Saccharomyces cerevisiae, produces an equimolar mixture of ethanol and CO2 through glucose, fructose or sucrose fermentation. In the present work, the inability of Z. mobilis to metabolize maltose has been circumvented by the addition of L. sanfranciscensis in the formulation. Indeed, L. sanfranciscensis, a heterofermentative lactic acid bacterium (LAB) typical of sourdough environment, hydrolyzes maltose releasing glucose which can be used by Z. mobilis for its metabolism. Biomass samples of Z. mobilis subs. mobilis DSM 424 and L. sanfranciscensis DSM 20663 were grown separately in liquid media and then associated in a model dough. Leavening trials set up by using three different microbial combinations (Lactobacillus:Zymomonas 80+80mg, 15+145mg and 145+15mg biomass, i.e. 1:1, 1:10 and 10:1 respectively on cell dry weight basis) evidenced CO2 production levels (mL) higher than the mathematical sum of CO2 produced by the single bacteria. In particular, when the biomass combination of L. sanfranciscensis and Z. mobilis was 1:1 (80+80mg cdw) and 10:1 (145+15mg cdw) a CO2 production of 46.3–41.4mL versus 26.7–28.5mL was achieved. The calculated productivity gain showed positive performances of the microbial combination up to 180–240min leavening. The subsequent efficiency loss may be due several factors, above all glucose shortage for Z. mobilis, as well as decrease of dough pH that can negatively affect both Lactobacillus and Zymomonas metabolism. As in traditional sourdoughs, L. sanfranciscensis was responsible for the souring activity with positive effects on both dough tasting and reduction of spoilage microbiota; Z. mobilis was instead responsible for most of the CO2 production. A bakery product leavened with the unconventional association Z. mobilis - L. sanfranciscensis will be addressed to people having adverse responses to the ingestion of bakery goods, thus providing innovation in the area of yeast-free leavened food.

      PubDate: 2016-08-18T16:22:00Z
  • Protease and lipase activities of fungal and bacterial strains derived
           from an artisanal raw ewe's milk cheese
    • Abstract: Publication date: 21 November 2016
      Source:International Journal of Food Microbiology, Volume 237
      Author(s): Sebnem Ozturkoglu-Budak, Ad Wiebenga, Peter A. Bron, Ronald P. de Vries
      We previously identified the microbiota present during cheese ripening and observed high protease and lipase activity in Divle Cave cheese. To determine the contribution of individual isolates to enzyme activities, we investigated a range of species representing this microbiota for their proteolytic and lipolytic ability. In total, 17 fungal, 5 yeast and 18 bacterial strains, previously isolated from Divle Cave cheese, were assessed. Qualitative protease and lipase activities were performed on skim-milk agar and spirit-blue lipase agar, respectively, and resulted in a selection of strains for quantitative assays. For the quantitative assays, the strains were grown on minimal medium containing irradiated Divle Cave cheese, obtained from the first day of ripening. Out of 16 selected filamentous fungi, Penicillium brevicompactum, Penicillium cavernicola and Penicillium olsonii showed the highest protease activity, while Mucor racemosus was the best lipase producer. Yarrowia lipolytica was the best performing yeast with respect to protease and lipase activity. From the 18 bacterial strains, 14 and 11 strains, respectively showed protease and lipase activity in agar plates. Micrococcus luteus, Bacillus stratosphericus, Brevibacterium antiquum, Psychrobacter glacincola and Pseudomonas proteolytica displayed the highest protease and lipase activity. The proteases of yeast and filamentous fungi were identified as mainly aspartic protease by specific inhibition with Pepstatin A, whereas inhibition by PMSF (phenylmethylsulfonyl fluoride) indicated that most bacterial enzymes belong to serine type protease. Our results demonstrate that aspartic proteases, which usually have high milk clotting activity, are predominantly derived from fungal strains, and therefore fungal enzymes appear to be more suitable for use in the cheese industry. Microbial enzymes studied in this research might be alternatives for rennin (chymosin) from animal source because of their low cost and stable availability. Future studies will aim to purify these enzymes to test their suitability for use in similar artisanal cheeses or in large scale commercial cheeses.

      PubDate: 2016-08-18T16:22:00Z
  • Conventional and molecular methods used in the detection and subtyping of
           Yersinia enterocolitica in food
    • Abstract: Publication date: 21 November 2016
      Source:International Journal of Food Microbiology, Volume 237
      Author(s): Stefanos Petsios, Maria Fredriksson-Ahomaa, Hercules Sakkas, Chrissanthy Papadopoulou

      PubDate: 2016-08-18T16:22:00Z
  • Mexican unpasteurised fresh cheeses are contaminated with Salmonella spp.,
           non-O157 Shiga toxin producing Escherichia coli and potential
           uropathogenic E. coli strains: A public health risk
    • Abstract: Publication date: 21 November 2016
      Source:International Journal of Food Microbiology, Volume 237
      Author(s): Rosa Guzman-Hernandez, Araceli Contreras-Rodriguez, Rosa Hernandez-Velez, Iza Perez-Martinez, Ahide Lopez-Merino, Mussaret B. Zaidi, Teresa Estrada-Garcia
      Fresh cheeses are a main garnish of Mexican food. Consumption of artisanal fresh cheeses is very common and most of them are made from unpasteurised cow milk. A total of 52 fresh unpasteurised cheeses of five different types were purchased from a variety of suppliers from Tabasco, Mexico. Using the most probable number method, 67% and 63% of samples were positive for faecal coliforms and E. coli, respectively; revealing their low microbiological quality. General hygienic conditions and practices of traditional cheese manufacturers were poor; most establishments had unclean cement floors, all lacked windows and doors screens, and none of the food-handlers wore aprons, surgical masks or bouffant caps. After analysing all E. coli isolates (121 strains) for the presence of 26 virulence genes, results showed that 9 (17%) samples were contaminated with diarrheagenic E. coli strains, 8 harboured non-O157 Shiga toxin producing E. coli (STEC), and one sample contained both STEC and diffusely adherent E. coli strains. All STEC strains carried the stx1 gene. Potential uropathogenic E. coli (UPEC) strains were isolated from 15 (29%) samples; the most frequent gene combination was fimA-agn43. Two samples were contaminated with Salmonella. The results demonstrated that unpasteurised fresh cheeses produced in Tabasco are of poor microbiological quality and may frequently harbour foodborne pathogens. Food safety authorities in Mexico need to conduct more rigorous surveillance of fresh cheeses. Furthermore, simple and inexpensive measures as establishing programs emphasizing good hand milking practices and hygienic manufacturing procedures may have a major effect on improving the microbiological quality of these food items.

      PubDate: 2016-08-18T16:22:00Z
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