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MICROBIOLOGY (221 journals)                  1 2 3     

Acta Microbiologica et Immunologica Hungarica     Full-text available via subscription   (Followers: 6)
Addiction Genetics     Open Access   (Followers: 3)
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: 3)
African Journal of Clinical and Experimental Microbiology     Open Access   (Followers: 1)
African Journal of Microbiology Research     Open Access   (Followers: 1)
Algorithms for Molecular Biology     Open Access   (Followers: 6)
American Journal of Infectious Diseases and Microbiology     Open Access   (Followers: 13)
American Journal of Microbiological Research     Open Access  
American Journal of Microbiology     Open Access   (Followers: 15)
American Journal of Molecular Biology     Open Access   (Followers: 3)
American Journal of Stem Cell Research     Open Access   (Followers: 1)
Annals of Clinical Microbiology and Antimicrobials     Open Access   (Followers: 5)
Annals of Microbiology     Hybrid Journal   (Followers: 9)
Annual Review of Microbiology     Full-text available via subscription   (Followers: 22)
Antimicrobial Agents and Chemotherapy     Full-text available via subscription   (Followers: 15)
Applied and Environmental Microbiology     Full-text available via subscription   (Followers: 24)
Applied Biochemistry and Microbiology     Hybrid Journal   (Followers: 7)
Applied Microbiology and Biotechnology     Hybrid Journal   (Followers: 24)
Archives of Microbiology     Hybrid Journal   (Followers: 4)
Avicenna Journal of Clinical Microbiology and Infection     Open Access  
Beneficial Microbes     Full-text available via subscription   (Followers: 2)
Bio-Research     Full-text available via subscription  
BioArchitecture     Full-text available via subscription  
Biocell     Open Access   (Followers: 1)
Bioethanol     Open Access  
Biomaterials Science     Full-text available via subscription   (Followers: 4)
Biomedical Research     Open Access   (Followers: 3)
BioMolecular Concepts     Full-text available via subscription   (Followers: 2)
Biomolecules     Open Access   (Followers: 1)
BMC Microbiology     Open Access   (Followers: 7)
Brazilian Journal of Microbiology     Open Access   (Followers: 2)
Canadian Journal of Infectious Diseases & Medical Microbiology     Hybrid Journal   (Followers: 1)
Canadian Journal of Microbiology     Full-text available via subscription   (Followers: 4)
Cell Biology : Research & Therapy     Partially Free  
Cell Host & Microbe     Full-text available via subscription   (Followers: 8)
Cell Medicine     Open Access  
Cell Regeneration     Open Access  
Cell Stem Cell     Full-text available via subscription   (Followers: 19)
CellBio     Open Access  
Cells     Open Access   (Followers: 1)
Cellular & Molecular Immunology     Hybrid Journal   (Followers: 8)
Cellular Microbiology     Hybrid Journal   (Followers: 5)
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: 14)
Clinical Microbiology Newsletter     Hybrid Journal   (Followers: 3)
Clinical Microbiology Reviews     Full-text available via subscription   (Followers: 10)
Comparative Immunology, Microbiology and Infectious Diseases     Hybrid Journal   (Followers: 8)
Computational Molecular Bioscience     Open Access   (Followers: 1)
Continental Journal of Microbiology     Open Access   (Followers: 3)
Critical Reviews in Microbiology     Hybrid Journal   (Followers: 6)
Current Issues in Molecular Biology     Open Access  
Current Microbiology     Hybrid Journal   (Followers: 5)
Current Molecular Imaging     Hybrid Journal  
Current Opinion in Microbiology     Hybrid Journal   (Followers: 15)
Current Tissue Engineering     Hybrid Journal   (Followers: 1)
Current Topics in Microbiology and Immunology     Hybrid Journal   (Followers: 4)
Diagnostic Microbiology and Infectious Disease     Hybrid Journal   (Followers: 3)
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: 7)
Environmental Microbiology Reports     Hybrid Journal   (Followers: 3)
Enzyme and Microbial Technology     Hybrid Journal   (Followers: 5)
Epigenetics of Degenerative Diseases     Open Access   (Followers: 3)
European Journal of Clinical Microbiology & Infectious Diseases     Hybrid Journal   (Followers: 11)
European Journal of Microbiology and Immunology     Open Access   (Followers: 6)
Experimental and Molecular Pathology     Hybrid Journal   (Followers: 2)
Fems Immunology & Medical Microbiology     Hybrid Journal   (Followers: 6)
Fems Microbiology Ecology     Hybrid Journal   (Followers: 6)
Fems Microbiology Letters     Hybrid Journal   (Followers: 13)
Fems Microbiology Reviews     Hybrid Journal   (Followers: 17)
Folia Histochemica et Cytobiologica     Open Access  
Folia Microbiologica     Hybrid Journal   (Followers: 1)
Food Microbiology     Hybrid Journal   (Followers: 12)
Frontiers in Cell and Developmental Biology     Open Access   (Followers: 1)
Frontiers in Cellular and Infection Microbiology     Open Access   (Followers: 2)
Frontiers in Cellular Neuroscience     Open Access  
Frontiers in Microbiology     Open Access   (Followers: 5)
Frontiers in Molecular Neuroscience     Open Access  
Future Microbiology     Full-text available via subscription   (Followers: 2)
Future Virology     Full-text available via subscription   (Followers: 4)
Gene Expression     Full-text available via subscription  
Genetica si Biologie Moleculara     Open Access   (Followers: 1)
Genetics and Molecular Research     Open Access   (Followers: 3)
Geomicrobiology Journal     Hybrid Journal   (Followers: 1)
Gut Microbes     Full-text available via subscription   (Followers: 2)
Indian Journal of Microbiology     Hybrid Journal   (Followers: 1)
Indian Journal of Pathology and Microbiology     Open Access   (Followers: 1)
Infection Ecology & Epidemiology     Open Access   (Followers: 6)
International Arabic Journal of Antimicrobial Agents     Open Access   (Followers: 5)
International Journal of Antimicrobial Agents     Hybrid Journal   (Followers: 2)
International Journal of Bacteriology     Open Access  
International Journal of Bioassays     Open Access   (Followers: 6)
International Journal of Biotechnology and Molecular Biology Research     Open Access  
International Journal of Food Microbiology     Hybrid Journal   (Followers: 11)
International Journal of Infection and Microbiology     Open Access   (Followers: 1)

        1 2 3     

Journal Cover International Journal of Food Microbiology
   [13 followers]  Follow    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
     ISSN (Print) 0168-1605
     Published by Elsevier Homepage  [2571 journals]   [SJR: 1.386]   [H-I: 108]
  • Temperature effect on high salinity depuration of Vibrio vulnificus and V.
           parahaemolyticus from the Eastern oyster (Crassostrea virginica)
    • Abstract: Publication date: 2 January 2015
      Source:International Journal of Food Microbiology, Volume 192
      Author(s): A.M. Larsen , F.S. Rikard , W.C. Walton , C.R. Arias
      Vibrio vulnificus (Vv) and Vibrio parahaemolyticus (Vp) are opportunistic human pathogens naturally associated with the Eastern oyster Crassostrea virginica. The abundances of both pathogens in oysters are positively correlated with temperature, thus ingestion of raw oysters during the warm summer months is a risk factor for contracting illness from these bacteria. Current post-harvest processing (PHP) methods for elimination of these pathogens are expensive and kill the oyster, changing their organoleptic properties and making them less appealing to some consumers. High salinity has proven effective in reducing Vv numbers in the wild and our research aims at developing an indoor recirculating system to reduce pathogenic Vibrios while maintaining the taste and texture of live oysters. The goal of this study was to determine the influence of temperature on the efficacy of high salinity depuration. Vv was enumerated as most probable number (MPN) per gram of oyster tissue using the FDA-approved modified cellobiose polymyxin colistin (mCPC) protocol and with an alternative Vibrio specific media CHROMagar™ Vibrio (CaV). CaV was also used to quantify Vp. Oysters were held at 35psu for 10days at three temperatures: low (20°C), mid (22.5°C) and high (25°C). There was no difference in MPN/g of Vv between media; however more Vv isolates were obtained from mCPC than CaV. There was no significant effect of temperature on reduction of Vv or Vp throughout depuration but there was a tendency for low temperatures to be less effective than the higher ones. High salinity resulted in a significant decrease in Vv by day 3 and again by day 10, and a decrease in Vp by day 3. Oyster condition indices were maintained throughout depuration and mortality was low (4% across three trials). Overall these results support the use of mCPC for Vv enumeration and demonstrate the promise of high salinity depuration for PHP of the Eastern oyster. The trend for lower temperatures to be less effective is surprising and indicates a potential interaction between salinity and temperature that should be further investigated.


      PubDate: 2014-10-12T20:35:37Z
       
  • In vitro determination of volatile compound development during starter
           culture-controlled fermentation of Cucurbitaceae cotyledons
    • Abstract: Publication date: 2 January 2015
      Source:International Journal of Food Microbiology, Volume 192
      Author(s): Aristide Guillaume Silapeux Kamda , Cíntia Lacerda Ramos , Elie Fokou , Whasley Ferreira Duarte , Achu Mercy , Kansci Germain , Disney Ribeiro Dias , Rosane Freitas Schwan
      The effects of Lactobacillus plantarum UFLA CH3, Pediococcus acidilactici UFLA BFFCX 27.1, and Torulaspora delbrueckii UFLA FFT2.4 inoculation on the volatile compound profile of fermentation of Cucumeropsis mannii cotyledons were investigated. Different microbial associations were used as starters. All associations displayed the ability to ferment the cotyledons as judged by lowering the pH from 6.4 to 4.4–5 within 24h and increasing organic acids such as lactate and acetate. The population of lactic acid bacteria (LAB) and yeasts increased during fermentation. In the fermentation performed without inoculation (control), the LAB and yeast populations were lower than those in inoculated assays at the beginning, but they reached similar populations after 48h. The Enterobacteriaceae population decreased during the fermentation, and they were not detected at 48h in the L. plantarum UFLA CH3 and P. acidilactici UFLA BFFCX 27.1 (LP+PA) and L. plantarum UFLA CH3, P. acidilactici UFLA BFFCX 27.1, and T. delbrueckii UFLA FFT2.4 (LP+PA+TD) samples. The assays inoculated with the yeast T. delbrueckii UFLA FFT2.4 exhibited the majority of volatile compounds (13 compounds) characterized by pleasant notes. The LP+PA+TD association seemed to be appropriate to ferment C. mannii cotyledons. It was able to control the Enterobacteriaceae population, and achieved high concentrations of esters and low concentrations of aldehydes and ketones.


      PubDate: 2014-10-12T20:35:37Z
       
  • Growth/no growth models for Zygosaccharomyces rouxii associated with
           acidic, sweet intermediate moisture food products
    • Abstract: Publication date: 2 January 2015
      Source:International Journal of Food Microbiology, Volume 192
      Author(s): C.L. Marvig , R.M. Kristiansen , D.S. Nielsen
      The most notorious spoilage organism of sweet intermediate moisture foods (IMFs) is Zygosaccharomyces rouxii, which can grow at low water activity, low pH and in the presence of organic acids. Together with an increased consumer demand for preservative free and healthier food products with less sugar and fat and a traditionally long self-life of sweet IMFs, the presence of Z. rouxii in the raw materials for IMFs has made assessment of the microbiological stability a significant hurdle in product development. Therefore, knowledge on growth/no growth boundaries of Z. rouxii in sweet IMFs is important to ensure microbiological stability and aid product development. Several models have been developed for fat based, sweet IMFs. However, fruit/sugar based IMFs, such as fruit based chocolate fillings and jams, have lower pH and aw than what is accounted for in previously developed models. In the present study growth/no growth models for acidified sweet IMFs were developed with the variables aw (0.65–0.80), pH (2.5–4.0), ethanol (0–14.5% (w/w) in water phase) and time (0–90days). Two different strains of Z. rouxii previously found to show pronounced resistance to the investigated variables were included in model development, to account for strain differences. For both strains data sets with and without the presence of sorbic acid (250ppm on product basis) were built. Incorporation of time as an exploratory variable in the models gave the possibility to predict the growth/no growth boundaries at each time between 0 and 90days without decreasing the predictive power of the models. The influence of ethanol and aw on the growth/no growth boundary of Z. rouxii was most pronounced in the first 30days and 60days of incubation, respectively. The effect of pH was almost negligible in the range of 2.5–4.0. The presence of low levels of sorbic acid (250ppm) eliminated growth of both strains at all conditions tested. The two strains tested have previously been shown to have similar tolerance towards the single stress factors included in the study, but when the stress factors were combined the two strains showed difference in their ability to grow illustrating the importance of including more strains when developing growth/no growth models. The developed models can be useful tools for development of new acidic sweet IMFs.


      PubDate: 2014-10-12T20:35:37Z
       
  • Batch testing for noroviruses in frozen raspberries
    • Abstract: Publication date: 2 January 2015
      Source:International Journal of Food Microbiology, Volume 192
      Author(s): Ann De Keuckelaere , Dan Li , Bart Deliens , Ambroos Stals , Mieke Uyttendaele
      Berries, in particular raspberries, have been associated with multiple recalls due to norovirus contamination and were linked to a number of norovirus (NoV) outbreaks. In the present study a total of 130 samples of frozen raspberries were collected from 26 batches in four different raspberry processing companies. In two companies the samples consisted of bulk frozen raspberries serving as raw material for the production of raspberry puree (an intermediate food product in a business to business setting). In two other companies, the samples consisted of bulk individually quick frozen (IQF) raspberries serving as raw material for the production of frozen fruit mixes (as a final food product for consumer). Enumeration of Escherichia coli and coliforms was performed as well as real-time reverse transcription PCR (RT-qPCR) detection of GI and GII NoV (in 2×10g). In addition, in cases where positive NoV GI or GII RT-qPCR signals were obtained, an attempt to sequence the amplicons was undertaken. Six out of 70 samples taken from the 14 batches of frozen raspberries serving raspberry puree production provided a NoV RT-qPCR signal confirmed by sequencing. Four of these six positive samples clustered in one batch whereas the other two positive samples clustered in another batch from the same company. All six positive samples showed NoV RT-qPCR signals above the limit of quantification of the RT-qPCR assay. These two positive batches of frozen raspberries can be classified as being of insufficient sanitary quality. The mean NoV level in 20g of these raspberry samples was 4.3 log genomic copies NoV GI/20g. The concern for public health is uncertain as NoV RT-qPCR detection is unable to discriminate between infectious and non-infectious virus particles. For the IQF raspberries, one batch out of 12 tested NoV positive, but only 1 out of the 5 samples analyzed in this batch showed a positive RT-qPCR GI NoV signal confirmed by sequencing. The RT-qPCR signal was below the limit of quantification of the assay used (<3.7 log genomic copies/20g). It was shown that the applied protocol for sequencing of the amplicon to confirm the specificity of the RT-qPCR signal was successful for GI NoV amplicons but often failed and provided an inconclusive result for GII NoV amplicons.


      PubDate: 2014-10-12T20:35:37Z
       
  • The effect of carvacrol on enteric viruses
    • Abstract: Publication date: 2 January 2015
      Source:International Journal of Food Microbiology, Volume 192
      Author(s): C. Sánchez , R. Aznar , G. Sánchez
      Carvacrol, a monoterpenic phenol, is said to have extensive antimicrobial activity in a wide range of food spoilage or pathogenic fungi, yeast and bacteria. The aim of this study was to assess its antiviral activity on norovirus surrogates, feline calicivirus (FCV), murine norovirus (MNV), and hepatitis A virus (HAV), as well as its potential in food applications. Initially, different concentrations of carvacrol (0.25, 0.5, 1%) were individually mixed with each virus at titers of ca. 6–7 log TCID50/ml and incubated 2h at 37°C. Carvacrol at 0.5% completely inactivated the two norovirus surrogates, whereas 1% concentration was required to achieve ca. 1 log reduction of HAV. In lettuce wash water, carvacrol efficacy on MNV was dependent on the chemical oxygen demand (COD), with no effect over 300ppm. A 4 log reduction in FCV infectivity was observed when 0.5% carvacrol was used to sanitize lettuce wash water, regardless of COD. Carvacrol was also evaluated as a natural disinfectant of produce, showing 1% carvacrol reduced inoculated NoV surrogates titers in lettuce by 1 log after 30min contact. These results represent a step forward in improving food safety by using carvacrol as an alternative natural additive to reduce viral contamination in the fresh vegetable industry.


      PubDate: 2014-10-12T20:35:37Z
       
  • Modelling of the growth/no growth interface of Wallemia sebi and Eurotium
           herbariorum as a function of pH, aw and ethanol concentration
    • Abstract: Publication date: 2 January 2015
      Source:International Journal of Food Microbiology, Volume 192
      Author(s): N. Deschuyffeleer , A. Vermeulen , J. Daelman , E. Castelein , M. Eeckhout , F. Devlieghere
      High sugar products (sugar content>50%) are generally considered to be stable against all forms of microbial spoilage during a prolonged shelf life of several months. However, one specific subgroup of micro-organisms, the xerophilic moulds, can develop quite fast on the surface of food products with a reduced water activity (<0.85). The chance whether these xerophilic moulds are able to grow on the food product depends on the combination of intrinsic factors (e.g., water activity and pH) and the storage conditions (e.g., temperature). This study examines the development of growth/no growth models for the xerophilic moulds Wallemia sebi and Eurotium herbariorum in a sugar rich broth. Growth/no growth models are predictive models that are designed to give a prediction about the probability of growth of a spoilage micro-organism under a specific set of environmental conditions. In this research, a water activity between 0.75 and 0.90, a pH between 5.0 and 6.2, an ethanol concentration between 0% and 5% (g EtOH/g H2O) and their interactions were tested. The inoculated media were stored at 22°C (±1°C) during a prolonged test period (up to 120days). The obtained models were also validated in a chocolate-based food product (ganache). The resulting growth/no growth models show that the growth of W. sebi and E. herbariorum can be inhibited for a prolonged time (>3months) if an ethanol concentration of 5% on the water phase is present in the food product, irrespective of water activity values between 0.89 and 0.755. The necessary amount of ethanol for shorter shelf lives can be calculated with the models that were built. Although the models have not been validated thoroughly in actual food products, the preliminary results that were obtained by testing the model on a ganache indicated that the models are capable of delivering safe predictions.


      PubDate: 2014-10-12T20:35:37Z
       
  • Guidelines for experimental design protocol and validation procedure for
           the measurement of heat resistance of microorganisms in milk
    • Abstract: Publication date: 2 January 2015
      Source:International Journal of Food Microbiology, Volume 192
      Author(s): Robin Condron , Choreh Farrokh , Kieran Jordan , Peter McClure , Tom Ross , Olivier Cerf
      Studies on the heat resistance of dairy pathogens are a vital part of assessing the safety of dairy products. However, harmonized methodology for the study of heat resistance of food pathogens is lacking, even though there is a need for such harmonized experimental design protocols and for harmonized validation procedures for heat treatment studies. Such an approach is of particular importance to allow international agreement on appropriate risk management of emerging potential hazards for human and animal health. This paper is working toward establishment of a harmonized protocol for the study of the heat resistance of pathogens, identifying critical issues for establishment of internationally agreed protocols, including a harmonized framework for reporting and interpretation of heat inactivation studies of potentially pathogenic microorganisms.


      PubDate: 2014-10-12T20:35:37Z
       
  • The involvement of bacterial quorum sensing in the spoilage of
           refrigerated Litopenaeus vannamei
    • Abstract: Publication date: 2 January 2015
      Source:International Journal of Food Microbiology, Volume 192
      Author(s): Suqin Zhu , Haohao Wu , Mingyong Zeng , Zunying Liu , Ying Wang
      Quorum-sensing signals in refrigerated shrimp (Litopenaeus vannamei) undergoing spoilage were examined using bioreporter assays, thin-layer chromatography and gas chromatography–mass spectrometry, and the results revealed the presence of three types of autoinducers including acetylated homoserine lactones (AHLs) (i.e., N-hexanoyl-homoserine lactone, N-oxohexanoyl-homoserine lactone and N-octanoyl-homoserine lactone), autoinducer-2, and cyclic dipeptides (i.e., cyclo-(l-Pro-l-Leu), cyclo-(l-Leu-l-Leu) and cyclo-(l-Pro-l-Phe)). Autoinducer-2, rather than any AHL, was detected in extracts from pure cultures of the specific spoilage organisms (SSO), i.e., Shewanella putrefaciens (SS01) and Shewanella baltica (SA02). As for the cyclic peptides, only SA02 was determined to produce cyclo-(l-Pro-l-Leu). According to the transcription levels of LuxR (the master quorum-sensing regulator) in the SSO in response to exogenous autoinducers, the SSO could sense AHLs and cyclo-(l-Leu-l-Leu), rather than autoinducer-2, cyclo-(l-Leu-l-Leu) and cyclo-(l-Pro-l-Phe). In accordance with the results of LuxR expression, the production of biofilm matrixes and extracellular proteases in the SSO was regulated by exogenous AHLs and cyclo-(l-Pro-l-Leu), rather than 4,5-dihydroxy-2,3-pentanedione (the autoinducer-2 precursor), cyclo-(l-Leu-l-Leu) and cyclo-(l-Pro-l-Phe). Exogenous N-hexanoyl-homoserine lactone and cyclo-(l-Pro-l-Leu) increased the growth rates and population percentages of the SSO in shrimp samples under refrigerated storage, and interestingly, exogenous 4,5-dihydroxy-2,3-pentanedione also increased the population percentages of the SSO in vivo by inhibiting the growth of the competing bacteria. However, according to the levels of TVB-N and the volatile organic components in the shrimp samples, exogenous 4,5-dihydroxy-2,3-pentanedione did not accelerate the shrimp spoilage process as N-hexanoyl-homoserine lactone and cyclo-(l-Pro-l-Leu) did. In summary, our results suggest that quorum sensing involves the spoilage of refrigerated Litopenaeus vannamei.


      PubDate: 2014-10-12T20:35:37Z
       
  • Control of cell morphology of probiotic Lactobacillus acidophilus for
           enhanced cell stability during industrial processing
    • Abstract: Publication date: 2 January 2015
      Source:International Journal of Food Microbiology, Volume 192
      Author(s): Martin Senz , Bernhard van Lengerich , Johannes Bader , Ulf Stahl
      The viability of bacteria during industrial processing is an essential quality criterion for bacterial preparations, such as probiotics and starter cultures. Therefore, producing stable microbial cultures during proliferation is of great interest. A strong correlation between the culture medium and cellular morphology was observed for the lactic acid bacterium Lactobacillus acidophilus NCFM, which is commonly used in the dairy industry as a probiotic supplement and as a starter culture. The cell shapes ranged from single short rods to long filamentous rods. The culture medium composition could control this phenomenon of pleomorphism, especially the use of peptone in combination with an adequate heating of the medium during preparation. Furthermore, we observed a correlation between the cell size and stability of the microorganisms during industrial processing steps, such as freeze-drying, extrusion encapsulation and storage following dried preparations. The results revealed that short cells are more stable than long cells during each of the industrially relevant processing steps. As demonstrated for L. acidophilus NCFM, the adaptation of the medium composition and optimized medium preparation offer the possibility to increase the concentration of viable cells during up- and survival rate during down-stream processing.


      PubDate: 2014-10-12T20:35:37Z
       
  • Static tank depuration and chronic short-term experimental contamination
           of Eastern oysters (Crassostrea virginica) with Giardia duodenalis cysts
    • Abstract: Publication date: 2 January 2015
      Source:International Journal of Food Microbiology, Volume 192
      Author(s): Jessica E. Willis , J.T. McClure , Carol McClure , Jonathan Spears , Jeff Davidson , Spencer J. Greenwood
      Cysts of the protozoan parasite Giardia have been detected in many bivalve shellfish species worldwide. The detection of zoonotic Giardia duodenalis assemblages A and B is of public health concern, yet there is limited data available demonstrating the bioaccumulation and elimination of Giardia cysts in bivalve shellfish. This study quantified G. duodenalis cysts that were filtered and retained by oysters (Crassostrea virginica) over a one week chronic exposure period, or 24hour exposure followed by a 6day depuration period, using static tank systems containing 10L of 29ppt water inoculated with 1000 or 10,000 cysts. Under chronic exposure, each oyster retained a mean of 13.4 and 87.4 cysts during the first 24h of exposure at low and high doses, respectively, and the cysts bioaccumulated at a rate of 1.2 and 6.8cysts/oyster/day, respectively, for the remaining duration of the trials. In acute exposure trials, oysters retained 13.8 cysts or 78.9 cysts at low and high doses, respectively, during the initial 24hour exposure and naturally depurated cysts at a rate of −0.92cysts/oyster/day and −2.2cysts/oyster/day, respectively, after transfer. Although most G. duodenalis cysts were eliminated within the first 24h via pseudofeces and feces, detection of some cysts in the fecal material on day 7 of acute exposure trials was indicative of cysts which passed through the digestive tract and released in feces. Only 48–53% of the initial tank inocula were recovered and may indicate that some cysts were selectively filtered by oysters but degraded through digestion.


      PubDate: 2014-10-12T20:35:37Z
       
  • Psychrotrophic lactic acid bacteria associated with production batch
           recalls and sporadic cases of early spoilage in Belgium between 2010 and
           2014
    • Abstract: Publication date: 17 November 2014
      Source:International Journal of Food Microbiology, Volume 191
      Author(s): Vasileios Pothakos , Bernard Taminiau , Geert Huys , Carine Nezer , Georges Daube , Frank Devlieghere
      Between 2010 and 2014 several spoilage cases in Belgium occurring in retail foodstuffs prior to the end of shelf-life have been reported to our laboratory. Overall, seven cases involved strictly psychrotrophic lactic acid bacteria (LAB) contamination in packaged and chilled-stored food products. The products derived either from recalls of entire production batches or as specimens of sporadic spoilage manifestations. Some of these samples were returned to the manufacturing companies by consumers who observed the alterations after purchasing the products. The products covered a wide range of foodstuffs (i.e. meat, dairy, vegetable, egg products and composite food) and denoted different spoilage defects. However, the microbiota determined by means of 16S rRNA gene high-throughput sequencing analysis underpin few LAB genera (i.e. Leuconostoc, Lactobacillus, Weissella and Lactococcus), which are frequently encountered nowadays as specific spoilage organisms (SSO) albeit overlooked by mesophilic enumeration methods due to their strictly psychrotrophic character. The present study confirms the spreading of psychrotrophic LAB in Belgian food processing environments leading to unexpected spoilage, corroborating their spoilage dynamics and prevalence in all kinds of packaged and refrigerated foodstuffs in Northern Europe.


      PubDate: 2014-10-02T20:11:40Z
       
  • Monoculture parameters successfully predict coculture growth kinetics of
           Bacteroides thetaiotaomicron and two Bifidobacterium strains
    • Abstract: Publication date: 17 November 2014
      Source:International Journal of Food Microbiology, Volume 191
      Author(s): A.S. Van Wey , A.L. Cookson , N.C. Roy , W.C. McNabb , T.K. Soboleva , P.R. Shorten
      Microorganisms rarely live in isolation but are most often found in a consortium. This provides the potential for cross-feeding and nutrient competition among the microbial species, which make it challenging to predict the growth kinetics in coculture. In this paper we developed a mathematical model to describe substrate consumption and subsequent microbial growth and metabolite production for bacteria grown in monoculture. The model characterized substrate utilization kinetics of 18 Bifidobacterium strains. Some bifidobacterial strains demonstrated preferential degradation of oligofructose in that sugars with low degree of polymerization (DP) (DP≤3 or 4) were metabolized before sugars of higher DP, or vice versa. Thus, we expanded the model to describe the preferential degradation of oligofructose. In addition, we adapted the model to describe the competition between human colonic bacteria Bacteroides thetaiotaomicron LMG 11262 and Bifidobacterium longum LMG 11047 or Bifidobacterium breve Yakult for inulin as well as cross-feeding of breakdown products from the extracellular hydrolysis of inulin by B. thetaiotaomicron LMG 11262. We found that the coculture growth kinetics could be predicted based on the respective monoculture growth kinetics. Using growth kinetics from monoculture experiments to predict coculture dynamics will reduce the number of in vitro experiments required to parameterize multi-culture models.


      PubDate: 2014-10-02T20:11:40Z
       
  • Selection of functional lactic acid bacteria as starter cultures for the
           fermentation of Korean leek (Allium tuberosum Rottler ex Sprengel.)
    • Abstract: Publication date: 17 November 2014
      Source:International Journal of Food Microbiology, Volume 191
      Author(s): Jaesik Yang , Yosep Ji , Hyunjoon Park , Jieun Lee , Soyoung Park , Soyoung Yeo , Hyunkil Shin , Wilhelm H. Holzapfel
      The purpose of this research was to find safe and suitable starter cultures for the fermentation of Korean leek (Allium tuberosum Rottler), also known as garlic chives or Oriental garlic. This traditional herb has several functional properties and a strong flavour; its leaves are used as food material. Eighteen strains of lactic acid bacteria (LAB) were isolated from well-fermented leek kimchi. Controlled fermentation of the leek leaves was conducted with 2 strains (Weissella confusa LK4 and Lactobacillus plantarum LK8), selected as potential starter cultures on the basis of their safety properties, and on the pH, total titratable acidity (TTA), and viable cell numbers [colony forming units (CFUml−1)] achieved during the fermentation. Microbial dynamics was also followed during fermentation by using PCR-DGGE (Denaturing Gradient Gel Electrophoresis) on DNA level. To analyse bioactive compounds such as thiols and allicin (diallyl thiosulfinates), the total flavonoid and polyphenolic contents were determined by colorimetric methods. Functional properties were assessed on the basis of anti-oxidative capacities by determining the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical-scavenging effect, and ferric reducing antioxidant power (FRAP). W. confusa LK4 rapidly increased during the first stage of leek fermentation, and was mainly responsible for accelerated fermentation during the early period in contrast to L. plantarum LK8, a stronger acid producer during the later stages of fermentation. After 48h fermentation, leeks fermented with W. confusa LK4 showed the highest radical scavenging effects and reducing ability. The detectable amount of allicin of fermented leeks decreased relative to the change in pH, whereas the concentration of thiols significantly increased. Total flavonoid and poly-phenolic contents changed during fermentation and showed correlation with anti-oxidant effects. We therefore suggest the suitability of W. confusa LK4 as a potential starter culture for fermentation of leeks.


      PubDate: 2014-10-02T20:11:40Z
       
  • Glutaminase-producing Meyerozyma (Pichia) guilliermondii isolated from
           Thai soy sauce fermentation
    • Abstract: Publication date: 2 January 2015
      Source:International Journal of Food Microbiology, Volume 192
      Author(s): Phichayaphorn Aryuman , Sittiwat Lertsiri , Wonnop Visessanguan , Nuttawee Niamsiri , Amaret Bhumiratana , Apinya Assavanig
      In this study, 34 yeast isolates were obtained from koji and moromi samples of Thai soy sauce fermentation. However, the most interesting yeast strain was isolated from the enriched 2month-old (M2) moromi sample and identified as Meyerozyma (Pichia) guilliermondii EM2Y61. This strain is a salt-tolerant yeast that could tolerate up to 20% (w/v) NaCl and produce extracellular and cell-bound glutaminases. Interestingly, its glutaminases were more active in 18% (w/v) NaCl which is a salt concentration in moromi. The extracellular glutaminase's activity was found to be much higher than that of cell-bound glutaminase. The highest specific activity and stability of the extracellular glutaminase were found in 18% (w/v) NaCl at pH4.5 and 37°C. A challenge test by adding partially-purified extracellular glutaminase from M. guilliermondii EM2Y61 into 1month-old (M1) moromi sample showed an increased conversion of l-glutamine to l-glutamic acid. This is the first report of glutaminase producing M. guilliermondii isolated from the moromi of Thai soy sauce fermentation. The results suggested the potential application of M. guilliermondii EM2Y61 as starter yeast culture to increase l-glutamic acid during soy sauce fermentation.


      PubDate: 2014-10-02T20:11:40Z
       
  • Selection of potential probiotic Enterococcus faecium isolated from
           Portuguese fermented food
    • Abstract: Publication date: 17 November 2014
      Source:International Journal of Food Microbiology, Volume 191
      Author(s): Joana Barbosa , Sandra Borges , Paula Teixeira
      Four Enterococcus faecium strains isolated from fermented products were evaluated for potential use as probiotic strains. In addition to efaAfm gene, commonly found in E. faecium food isolates, none of the isolates possessed virulence genes and none had positive reactions for the production of tyramine, histamine, putrescine and cadaverine in the screening medium used. All of these four isolates proved to be resistant to 65°C. E. faecium 119 did not show antimicrobial activity against any of the target bacteria investigated. E. faecium 85 and 101 inhibited Listeria innocua and E. faecium DSMZ 13590. The strain E. faecium 120 inhibited seven target bacteria (Listeria monocytogenes 7946, L. monocytogenes 7947, L. innocua 2030c, L. innocua NCTC 11286, E. faecium DSMZ 13590, Enterococcus faecalis ATCC 29212 and Staphylococcus aureus ATCC 29213) and was chosen as the representative to assess the ability to survive gastrointestinal tract passage simulation, as well as the protective role of two food matrices (skim milk and Alheira) during its passage. For both matrices used, no significant differences (p <0.05) were obtained between the types of digestion — quick and slow passage simulation. In the skim milk matrix the isolate was reduced to values below the detection limit of the enumeration technique by the end of the two digestions, in contrast to the Alheira matrix, for which isolate 120 showed a reduction of only ca. 1logCFU/ml. The E. faecium strain 120 was shown to be a potential candidate for further investigations as a potential probiotic culture.


      PubDate: 2014-10-02T20:11:40Z
       
  • Occurrence of anisakid nematode larvae in chub mackerel (Scomber
           japonicus) caught off Korea
    • Abstract: Publication date: 17 November 2014
      Source:International Journal of Food Microbiology, Volume 191
      Author(s): Tae-Jong Bak , Chan-Hyeok Jeon , Jeong-Ho Kim
      Chub mackerel (Scomber japonicus) is a pelagic fish species widely distributing in the Indo-Pacific and a commercially important fish species in Korea. It is known to harbor anisakid nematodes larvae, and ingesting the raw or undercooked fish can accidentally cause human infection. In this study, we isolated the nematode larvae in 417 chub mackerel caught from 7 sampling locations around the Korean Peninsula in 2011 and 2012, and identified them by PCR-RFLP of the ITS (internal transcribed spacer) of ribosomal DNA and the direct sequencing of the mitochondrial DNA cox2 gene. The prevalence of infection was 55.4% (231/417) and the mean intensity was 7.0 (1628/231). Most of the nematodes (1523/1628; 93.6%) were found in the body cavity, while 5.5% (89/1628) were found in the gastrointestinal tract. Four different species were identified by PCR-RFLP and direct sequencing. Most of the nematodes (1535/1628; 94.3%) were identified as Anisakis pegreffii, and 2.8% (46/1628) were identified as Hysterothylacium sp. A hybrid genotype (Anisakis simplex sensu stricto× A. pegreffii) and A. simplex sensu stricto were 2.5% (41/1628) and 0.4% (6/1628) of the identified nematodes, respectively. The anisakid nematode assemblage of chub mackerel in Korea was similar to that of chub mackerel from the Tsushima Current stock in Japan, in that A. pegreffii was the dominant species. Since most of the anisakid nematodes were found in the body cavity and most of them were identified as A. pegreffii or Hysterothylacium sp. by PCR-RFLP and direct sequencing, chub mackerel may not greatly contribute to human anisakidosis in Korea. Alternately, A. pegreffii may be responsible for human anisakidosis in Korea, in addition to A. simplex sensu stricto. Further studies, such as the molecular diagnosis of human anisakidosis, are necessary for assessing the epidemiological role of chub mackerel in Korea.


      PubDate: 2014-10-02T20:11:40Z
       
  • Oxidative stress induces the biosynthesis of citrinin by Penicillium
           verrucosum at the expense of ochratoxin
    • Abstract: Publication date: 2 January 2015
      Source:International Journal of Food Microbiology, Volume 192
      Author(s): Markus Schmidt-Heydt , Dominic Stoll , Peter Schütz , Rolf Geisen
      Penicillium verrucosum is a fungus that can produce ochratoxin A and citrinin, two structurally related nephrotoxic mycotoxins. P. verrucosum usually occurs on wheat but can occasionally also be found in NaCl rich habitats such as salted cheeses or olives, indicating that this fungus can adapt to different environments. The ratio of ochratoxin A to citrinin produced by P. verrucosum is shifted to one of either mycotoxin at the expense of the other dependent on the environmental conditions. High NaCl concentrations shift secondary metabolite biosynthesis towards ochratoxin A production. P. verrucosum copes with NaCl stress by increased ochratoxin A biosynthesis, ensuring chloride homeostasis. Ochratoxin A carries chlorine in its molecule and can excrete chlorine from the cell. It was further shown that the regulation of ochratoxin A by high NaCl conditions is mediated by the HOG MAP kinase signal transduction pathway. Here it is shown that high oxidative stress conditions, evoked for example by increasing concentrations of Cu2+ cations in the growth medium, shift secondary metabolite biosynthesis of P. verrucosum from ochratoxin A to citrinin. The production of citrinin normalizes the oxidative status of the fungal cell under oxidative stress conditions leading to an adaptation to these environmental conditions and protects against increased oxidative stress caused by increased Cu2+ concentrations. Moreover citrinin also protects against light of short wavelength, which may also increase the oxidative status of the environment. The biosynthesis of citrinin is apparently regulated by a cAMP/PKA signaling pathway, because increasing amounts of external cAMP reduce citrinin biosynthesis in a concentration dependent manner. These conditions lead to the cross-regulation of the ochratoxin A/citrinin secondary metabolite pair and support the adaptation of P. verrucosum to different environments.


      PubDate: 2014-10-02T20:11:40Z
       
  • Multilocus sequence typing reveals genetic diversity of foodborne
           Arcobacter butzleri isolates in the North of Spain
    • Abstract: Publication date: 17 November 2014
      Source:International Journal of Food Microbiology, Volume 191
      Author(s): Rodrigo Alonso , Cecilia Girbau , Irati Martinez-Malaxetxebarria , Aurora Fernández-Astorga
      The emerging pathogen Arcobacter butzleri is being increasingly isolated from different animal food products but the routes of its transmission to human are not well established yet. Typing methods would be useful in gaining such knowledge. Here we report the great genetic diversity observed among A. butzleri isolates from different food products. Forty-five isolates were analyzed by Multilocus Sequence Typing (MLST). A total of 157 alleles were identified across all seven loci, ranging from 16 alleles at glnA to 31 at glyA. MLST differentiated the isolates into 34 sequence types (STs), with the majority of isolates containing a unique sequence type. Seventy-four new alleles were identified, which resulted in the assignment of 33 new STs. No association of alleles or STs with food source was observed. For the first time, lateral gene transfer from Arcobacter skirrowii to A. butzleri at the glyA locus is also reported.


      PubDate: 2014-09-28T20:00:26Z
       
  • Co-occurrence of free-living protozoa and foodborne pathogens on
           dishcloths: Implications for food safety
    • Abstract: Publication date: 17 November 2014
      Source:International Journal of Food Microbiology, Volume 191
      Author(s): N. Chavatte , J. Baré , E. Lambrecht , I. Van Damme , M. Vaerewijck , K. Sabbe , K. Houf
      In the present study, the occurrence of free-living protozoa (FLP) and foodborne bacterial pathogens on dishcloths was investigated. Dishcloths form a potentially important source of cross-contamination with FLP and foodborne pathogens in food-related environments. First various protocols for recovering and quantifying FLP from dishcloths were assessed. The stomacher technique is recommended to recover flagellates and amoebae from dishcloths. Ciliates, however, were more efficiently recovered using centrifugation. For enumeration of free-living protozoa on dishcloths, the Most Probable Number method is a convenient method. Enrichment was used to assess FLP diversity on dishcloths (n=38). FLP were found on 89% of the examined dishcloths; 100% of these tested positive for amoebae, 71% for flagellates and 47% for ciliates. Diversity was dominated by amoebae: vahlkampfiids, vannellids, Acanthamoeba spp., Hyperamoeba sp. and Vermamoeba vermiformis were most common. The ciliate genus Colpoda was especially abundant on dishcloths while heterotrophic nanoflagellates mainly belonged to the genus Bodo, the glissomonads and cercomonads. The total number of FLP in used dishcloths ranged from 10 to 104 MPN/cm2. Flagellates were the most abundant group, and ciliates the least abundant. Detergent use was identified as a prime determinant of FLP concentrations on used dishcloths. Bacterial load on dishcloths was high, with a mean total of aerobic bacteria of 7.47log10 cfu/cm2. Escherichia coli was detected in 68% (26/38) of the used dishcloths, with concentrations up to 4log10 cfu/cm2. Foodborne pathogens including Staphylococcus aureus (19/38), Arcobacter butzleri (5/38) and Salmonella enterica subsp. enterica ser. Halle (1/38) were also present. This study showed for the first time that FLP, including some opportunistic pathogens, are a common and diverse group on dishcloths. Moreover, important foodborne pathogens are also regularly recovered. This simultaneous occurrence makes dishcloths a potential risk factor for cross-contamination and a microbial niche for bacteria–FLP interactions.


      PubDate: 2014-09-28T20:00:26Z
       
  • Cold stress improves the ability of Lactobacillus plantarum L67 to survive
           freezing
    • Abstract: Publication date: 17 November 2014
      Source:International Journal of Food Microbiology, Volume 191
      Author(s): Sooyeon Song , Dong-Won Bae , Kwangsei Lim , Mansel W. Griffiths , Sejong Oh
      The stress resistance of bacteria is affected by the physiological status of the bacterial cell and environmental factors such as pH, salts and temperature. In this study, we report on the stress response of Lactobacillus plantarum L67 after four consecutive freeze–thaw cycles. The cold stress response of the cold-shock protein genes (cspC, cspL and cspP) and ATPase activities were then evaluated. The cold stress was adjusted to 5°C when the bacteria were growing at the mid-exponential phase. A comparative proteomic analysis was performed with two-dimensional gel electrophoresis (2D SDS-PAGE) and a matrix assisted laser desorption/ionization-mass spectrometer. Only 56% of the L. plantarum L67 cells without prior exposure to cold stress survived after four consecutive freeze–thaw cycles. However, 78% of the L. plantarum L67 cells that were treated with cold stress at 5°C for 6h survived after freeze–thaw conditions. After applying cold stress to the culture for 6h, the cells were then stored for 60days at 5°C, 25°C and 35°C separately. The cold-stressed culture of L. plantarum L67 showed an 8% higher viability than the control culture. After applying cold stress for 6h, the transcript levels of two genes (cspP and cspL) were up-regulated 1.4 (cspP) and 1.2 (cspL) times compared to the control. However, cspC was not up-regulated. A proteomic analysis showed that the proteins increased after a reduction of the incubation temperature to 5°C. The importance of the expression of 13 other relevant proteins was also determined through the study. The exposure of L. plantarum cells to low temperatures aids their ability to survive through subsequent freeze–thaw processes and lyophilization.


      PubDate: 2014-09-28T20:00:26Z
       
  • Inactivation of Escherichia coli O157:H7 in biofilm on food-contact
           surfaces by sequential treatments of aqueous chlorine dioxide and drying
    • Abstract: Publication date: 17 November 2014
      Source:International Journal of Food Microbiology, Volume 191
      Author(s): Jihyun Bang , Ayoung Hong , Hoikyung Kim , Larry R. Beuchat , Min Suk Rhee , Younghoon Kim , Jee-Hoon Ryu
      We investigated the efficacy of sequential treatments of aqueous chlorine and chlorine dioxide and drying in killing Escherichia coli O157:H7 in biofilms formed on stainless steel, glass, plastic, and wooden surfaces. Cells attached to and formed a biofilm on wooden surfaces at significantly (P ≤0.05) higher levels compared with other surface types. The lethal activities of sodium hypochlorite (NaOCl) and aqueous chlorine dioxide (ClO2) against E. coli O157:H7 in a biofilm on various food-contact surfaces were compared. Chlorine dioxide generally showed greater lethal activity than NaOCl against E. coli O157:H7 in a biofilm on the same type of surface. The resistance of E. coli O157:H7 to both sanitizers increased in the order of wood>plastic>glass>stainless steel. The synergistic lethal effects of sequential ClO2 and drying treatments on E. coli O157:H7 in a biofilm on wooden surfaces were evaluated. When wooden surfaces harboring E. coli O157:H7 biofilm were treated with ClO2 (200μg/ml, 10min), rinsed with water, and subsequently dried at 43% relative humidity and 22°C, the number of E. coli O157:H7 on the surface decreased by an additional 6.4CFU/coupon within 6h of drying. However, when the wooden surface was treated with water or NaOCl and dried under the same conditions, the pathogen decreased by only 0.4 or 1.0logCFU/coupon, respectively, after 12h of drying. This indicates that ClO2 treatment of food-contact surfaces results in residual lethality to E. coli O157:H7 during the drying process. These observations will be useful when selecting an appropriate type of food-contact surfaces, determining a proper sanitizer for decontamination, and designing an effective sanitization program to eliminate E. coli O157:H7 on food-contact surfaces in food processing, distribution, and preparation environments.


      PubDate: 2014-09-28T20:00:26Z
       
  • Salmonella source attribution based on microbial subtyping: Does including
           data on food consumption matter'
    • Abstract: Publication date: 17 November 2014
      Source:International Journal of Food Microbiology, Volume 191
      Author(s): Lapo Mughini-Gras , Wilfrid van Pelt
      Source attribution based on microbial subtyping is being performed in many countries to ascertain the main reservoirs of human salmonellosis and to assess the impact of food safety interventions. To account for differences in exposure, the amount of food available for consumption within a country is often included in Salmonella source attribution models along with the level of contamination. However, not all foods have an equal probability of serving as vehicles for salmonellas, as some foods are more likely to be consumed raw/undercooked than others, posing a relatively higher risk. Using Salmonella data from the Netherlands in 2001–2004, this study aims at elucidating whether and how the incorporation of food consumption data in two source attribution models – the (modified) Dutch and Hald models – affects their attributions. We also propose the incorporation of an additional parameter to weight the amount of food consumed by its likelihood to be consumed raw/undercooked by the population. Incorporating the amount of food consumed caused a drastic change in the ranking of the top reservoirs in the Dutch model, but not in the Hald model, which proved to be insensitive to additional weightings given that its source-dependent factor can account for both food consumption and the ability for foods to serve as vehicles for salmonellas. Compared to attributions without food consumption, the Dutch model including the amount of food consumed showed an increase in the percentage of cases attributable to pigs and a decrease in that of layers/eggs, which became the second reservoir, after pigs. This was not consistent with established knowledge indicating that layers/eggs, rather than pigs, were the main reservoir of human salmonellosis in that period. By incorporating the additional weight reflecting the likelihood for different foods to be consumed raw/undercooked, the attributions of the Dutch model were effectively adjusted, both in terms of ranking and percent contributions of the different reservoirs. We concluded that incorporating food consumption data in the Dutch model can significantly affect the results. Therefore, such data should be either excluded from this model or used together with an additional weight able to adjust the amount of food consumed by its likelihood to be consumed insufficiently cooked. This may help identifying the correct reservoirs, allowing attributions to more closely reflect the real chance for a given food to serve as a vehicle for salmonellas. Conversely, the Hald model works properly irrespective of inclusion of food consumption data.


      PubDate: 2014-09-28T20:00:26Z
       
  • Identification of lactobacilli with inhibitory effect on biofilm formation
           by pathogenic bacteria on stainless steel surfaces
    • Abstract: Publication date: 17 November 2014
      Source:International Journal of Food Microbiology, Volume 191
      Author(s): Fatma Ait Ouali , Imad Al Kassaa , Benoit Cudennec , Marwan Abdallah , Farida Bendali , Djamila Sadoun , Nour-Eddine Chihib , Djamel Drider
      Two hundred and thirty individual clones of microorganisms were recovered from milk tanks and milking machine surfaces at two distinct farms (Bejaja City, Algeria). Of these clones, 130 were identified as lactic acid bacteria (LAB). In addition Escherichia coli, Salmonella, Staphylococcus aureus and Pseudomonas aeruginosa species were identified in the remaining 100 isolates—spoilage isolate. These isolates were assayed for ability to form biofilms. S. aureus, Lactobacillus brevis strains LB1F2, LB14F1 and LB15F1, and Lactobacillus pentosus strains LB2F2 and LB3F2 were identified as the best biofilm formers. Besides, these LAB isolates were able to produce proteinaceous substances with antagonism against the aforementioned spoilage isolates, when grown in MRS or TSB-YE media. During the screening, L. pentosus LB3F2 exhibited the highest antibacterial activity when grown in TSB-YE medium at 30°C. Additionally, L. pentosus LB3F2 was able to strongly hamper the adhesion of S. aureus SA3 on abiotic surfaces as polystyrene and stainless steel slides. LAB isolates did not show any hemolytic activity and all of them were sensitive to different families of antibiotic tested. It should be pointed out that LB3F2 isolate was not cytotoxic on the intestinal cells but could stimulate their metabolic activity. This report unveiled the potential of LB1F2, LB14F1, LB15F1, LB2F2, and LB3F2 isolates to be used as natural barrier or competitive exclusion organism in the food processing sector as well as a positive biofilm forming bacteria.


      PubDate: 2014-09-28T20:00:26Z
       
  • Adhesion of Salmonella Enteritidis and Listeria monocytogenes on stainless
           steel welds
    • Abstract: Publication date: 17 November 2014
      Source:International Journal of Food Microbiology, Volume 191
      Author(s): Letícia Sopeña Casarin , Adriano Brandelli , Fabrício de Oliveira Casarin , Paulo Azevedo Soave , Cesar Henrique Wanke , Eduardo Cesar Tondo
      Pathogenic microorganisms are able to adhere on equipment surfaces, being possible to contaminate food during processing. Salmonella spp. and Listeria monocytogenes are important pathogens that can be transmitted by food, causing severe foodborne diseases. Most surfaces of food processing industry are made of stainless steel joined by welds. However currently, there are few studies evaluating the influence of welds in the microorganism's adhesion. Therefore the purpose of the present study was to investigate the adhesion of Salmonella Enteritidis and L. monocytogenes on surface of metal inert gas (MIG), and tungsten inert gas (TIG) welding, as well as to evaluate the cell and surface hydrophobicities. Results demonstrated that both bacteria adhered to the surface of welds and stainless steel at same levels. Despite this, bacteria and surfaces demonstrated different levels of hydrophobicity/hydrophilicity, results indicated that there was no correlation between adhesion to welds and stainless steel and the hydrophobicity.


      PubDate: 2014-09-28T20:00:26Z
       
  • Safety assessment of greenhouse hydroponic tomatoes irrigated with
           reclaimed and surface water
    • Abstract: Publication date: 17 November 2014
      Source:International Journal of Food Microbiology, Volume 191
      Author(s): Francisco Lopez-Galvez , Ana Allende , Francisco Pedrero-Salcedo , Juan Jose Alarcon , Maria Isabel Gil
      The impact of reclaimed and surface water on the microbiological safety of hydroponic tomatoes was assessed. Greenhouse tomatoes were irrigated with reclaimed and surface water and grown on two hydroponic substrates (coconut fiber and rock wool). Water samples (n=208) were taken from irrigation water, with and without the addition of fertilizers and drainage water, and hydroponic tomatoes (n=72). Samples were analyzed for indicator microorganisms, generic Escherichia coli and Listeria spp., and pathogenic bacteria such as Salmonella spp. and Shiga-toxigenic E. coli (STEC), using multiplex real-time PCR (RT-PCR) after enrichment. The correlation between climatological parameters such as temperature and the levels of microorganisms in water samples was also determined. In irrigation water, generic E. coli counts were higher in reclaimed than in surface water whereas Listeria spp. numbers increased after adding the fertilizers in both water sources. In drainage water, no clear differences in E. coli and Listeria numbers were observed between reclaimed and surface water. No positive samples for STEC were found in irrigation water. Presumptive positives for Salmonella spp. were found in 7.7% of the water samples and 62.5% of these samples were reclaimed water. Salmonella-positive samples by RT-PCR could not be confirmed by conventional methods. Higher concentrations of E. coli were associated with Salmonella-presumptive positive samples. Climatological parameters, such as temperature, were not correlated with the E. coli and Listeria spp. counts. Tomato samples were negative for bacterial pathogens, while generic E. coli and Listeria spp. counts were below the detection limit. The prevalence of presumptive Salmonella spp. found in irrigation water (reclaimed and surface water) was high, which might present a risk of contamination. The absence of pathogens on greenhouse hydroponic tomatoes indicates that good agricultural practices (GAP) were in place, avoiding the microbial contamination of the fruit.


      PubDate: 2014-09-28T20:00:26Z
       
  • Antibacterial and physical effects of modified chitosan based-coating
           containing nanoemulsion of mandarin essential oil and three non-thermal
           treatments against Listeria innocua in green beans
    • Abstract: Publication date: 17 November 2014
      Source:International Journal of Food Microbiology, Volume 191
      Author(s): Renato Severino , Khanh Dang Vu , Francesco Donsì , Stephane Salmieri , Giovanna Ferrari , Monique Lacroix
      The antimicrobial activity against Listeria innocua of three different combined non-thermal treatments, along with the impact on color and texture on green bean samples, was evaluated. In this study a bioactive coating formulation based on modified chitosan containing 0.05% nanoemulsion of mandarin essential oil was tested in combination with γ-irradiation, UV-C and ozonated water treatments, and the results in terms of antimicrobial activity, color and texture changes, were evaluated during 14days storage. The combined coating and γ-irradiation treatment gave promising results, showing 3.3 log CFU/g initial microbial reduction, and exhibiting a strong synergistic antimicrobial effect. The treatment based on UV-C and coating formulation allowed a 3 log CFU/g reduction of initial L. innocua population on samples, showing a good residual antimicrobial activity and preventing loss of firmness and color changes during storage. The combined treatment of coating and ozonated water did not show any synergistic or additive antimicrobial effect, but they showed an impact on firmness and color. In conclusion UV-C and γ-irradiation treatments, in combination with the bioactive coating, represent an effective approach to control the growth of L. innocua on vegetable foods.


      PubDate: 2014-09-24T19:37:41Z
       
  • Antimicrobial properties of nisin after glycation with lactose,
           maltodextrin and dextran and the thyme oil emulsions prepared thereof
    • Abstract: Publication date: 17 November 2014
      Source:International Journal of Food Microbiology, Volume 191
      Author(s): Huaiqiong Chen , P. Michael Davidson , Qixin Zhong
      To clarify the reported conflicting antimicrobial activities of nisin after glycation, nisin was glycated with lactose, maltodextrin, and dextran at 70°C and 50% relative humidity for 1–24h. Nisin before and after glycation was studied for the first time to prepare thyme oil emulsions. The activity of glycated nisin and the thyme oil emulsions was tested in both tryptic soy broth (TSB) and 2% reduced fat milk. Results showed that nisin glycated with a smaller saccharide for a longer duration had a higher degree of glycation and the reduced number of positive charges lowered its antibacterial activity. The emulsified thyme oil had an additive effect with either glycated or native nisin against Listeria monocytogenes Scott A and Bacillus subtilis in TSB and 2% reduced fat milk. However, emulsions were less effective against L. monocytogenes Scott A in milk than same units of native nisin and same concentration of free thyme oil, likely due to the reduced availability of thymol and carvacrol, the main components of thyme oil. These results showed that glycation of nisin cannot broaden its antimicrobial activity and nisin is not a good compound to prepare emulsions of essential oils.


      PubDate: 2014-09-20T19:36:03Z
       
  • Bacteriophage P22 to challenge Salmonella in foods
    • Abstract: Publication date: 17 November 2014
      Source:International Journal of Food Microbiology, Volume 191
      Author(s): Paola Zinno , Chiara Devirgiliis , Danilo Ercolini , Duncan Ongeng , Gianluigi Mauriello
      In this study we considered the influence of phage addition on the fate of Salmonella enterica serovar Typhimurium in different foods. Phage P22 was applied to the following: liquid eggs, energy drinks, whole and skimmed milk, apple juice, chicken breast and chicken mince all spiked with its host, whose growth was monitored for 24 and 48h at 4°C. Appreciable host inactivation, generally in the order of 2 log cycles, was achieved compared to phage-free controls in all food matrices when 104 UFC/g host inoculum was used. Furthermore, wild food strains belonging to the serotypes Typhimurium, Enteritidis, Derby Give, Newport, Muenchen and Muenster were assayed towards phage P22. Only isolates of Salmonella Typhimurium as well as Salmonella Derby and Salmonella Enteritidis was inhibited by the presence of P22 phage. Additional challenge experiments were carried out by spiking liquid-eggs, chicken breast and chicken mince with mixes of wild Salmonella Typhimurium (at concentration of about 104 UFC/g) strains along with their relative phage P22. The results showed a reduction of 2–3 log cycles after 48h at 4°C depending on both mix of strains and the specific food. Overall, the results indicate that phages may be useful in the control of food-borne pathogens. The food matrices considered, the liquid more than the solid, do not seem to affect the phage ability of infection compared to similar tests performed in vitro.


      PubDate: 2014-09-20T19:36:03Z
       
  • Great interspecies and intraspecies diversity of dairy propionibacteria in
           the production of cheese aroma compounds
    • Abstract: Publication date: 17 November 2014
      Source:International Journal of Food Microbiology, Volume 191
      Author(s): Alyson L. Yee , Marie-Bernadette Maillard , Nathalie Roland , Victoria Chuat , Aurélie Leclerc , Tomislav Pogačić , Florence Valence , Anne Thierry
      Flavor is an important sensory property of fermented food products, including cheese, and largely results from the production of aroma compounds by microorganisms. Propionibacterium freudenreichii is the most widely used species of dairy propionibacteria; it has been implicated in the production of a wide variety of aroma compounds through multiple metabolic pathways and is associated with the flavor of Swiss cheese. However, the ability of other dairy propionibacteria to produce aroma compounds has not been characterized. This study sought to elucidate the effect of interspecies and intraspecies diversity of dairy propionibacteria on the production of aroma compounds in a cheese context. A total of 76 strains of Propionibacterium freudenreichii, Propionibacterium jensenii, Propionibacterium thoenii, and Propionibacterium acidipropionici were grown for 15days in pure culture in a rich medium derived from cheese curd. In addition, one strain each of two phylogenetically related non-dairy propionibacteria, Propionibacterium cyclohexanicum and Propionibacterium microaerophilum were included. Aroma compounds were analyzed using headspace trap-gas chromatography-mass spectrometry (GC–MS). An analysis of variance performed on GC–MS data showed that the abundance of 36 out of the 45 aroma compounds detected showed significant differences between the cultures. A principal component analysis (PCA) was performed for these 36 compounds. The first two axes of the PCA, accounting for 60% of the variability between cultures, separated P. freudenreichii strains from P. acidipropionici strains and also differentiated P. freudenreichii strains from each other. P. freudenreichii strains were associated with greater concentrations of a variety of compounds, including free fatty acids from lipolysis, ethyl esters derived from these acids, and branched-chain acids and alcohols from amino acid catabolism. P. acidipropionici strains produced less of these compounds but more sulfur-containing compounds from methionine catabolism. Meanwhile, branched-chain aldehydes and benzaldehyde were positively associated with certain strains of P. jensenii and P. thoenii. Moreover, the production of compounds with a common origin was correlated. Compound abundance varied significantly by strain, with fold changes between strains of the same species as high as in the order of 500 for a single compound. This suggests that the diversity of dairy propionibacteria can be exploited to modulate the flavor of mild cheeses.


      PubDate: 2014-09-20T19:36:03Z
       
  • Mupirocin-mucin agar for selective enumeration of Bifidobacterium bifidum
    • Abstract: Publication date: 17 November 2014
      Source:International Journal of Food Microbiology, Volume 191
      Author(s): Radko Pechar , Vojtech Rada , Lucia Parafati , Sarka Musilova , Vera Bunesova , Eva Vlkova , Jiri Killer , Jakub Mrazek , Vladimir Kmet , Roman Svejstil
      Bifidobacterium bifidum is a bacterial species exclusively found in the human intestinal tract. This species is becoming increasingly popular as a probiotic organism added to lyophilized products. In this study, porcine mucin was used as the sole carbon source for the selective enumeration of B. bifidum in probiotic food additives. Thirty-six bifidobacterial strains were cultivated in broth with mucin. Only 13 strains of B. bifidum utilized the mucin to produce acids. B. bifidum was selectively enumerated in eight probiotic food supplements using agar (MM agar) containing mupirocin (100mg/L) and mucin (20g/L) as the sole carbon source. MM agar was fully selective if the B. bifidum species was presented together with Bifidobacterium animalis subsp. lactis, Bifidobacterium breve, and Bifidobacterium longum subsp. longum species and with lactic acid bacteria (lactobacilli, streptococci). Isolated strains of B. bifidum were identified using biochemical, PCR, MALDI-TOF procedures and 16S rRNA gene sequencing. The novel selective medium was also suitable for the isolation of B. bifidum strains from human fecal samples.


      PubDate: 2014-09-16T19:21:42Z
       
  • Editorial Board
    • Abstract: Publication date: 3 November 2014
      Source:International Journal of Food Microbiology, Volume 190




      PubDate: 2014-09-16T19:21:42Z
       
  • Control of Listeria monocytogenes in fresh cheese using protective lactic
           acid bacteria
    • Abstract: Publication date: 17 November 2014
      Source:International Journal of Food Microbiology, Volume 191
      Author(s): M.C. Coelho , C.C.G. Silva , S.C. Ribeiro , M.L.N.E. Dapkevicius , H.J.D. Rosa
      In the past years, there has been a particular focus on the application of bacteriocins produced by lactic acid bacteria (LAB) in controlling the growth of pathogenic bacteria in foods. The aim of this study was to select LAB strains with antimicrobial activity, previously isolated from a traditional Azorean artisanal cheese (Pico cheese), in order to identify those with the greatest potential in reducing Listeria monocytogenes in fresh cheese. Eight bacteriocin producer strains identified as Lactococcus lactis (1) and Enterococcus faecalis (7) were tested. In general, the bacteriocin-producing strains presented a moderate growth in fresh cheese at refrigeration temperatures (4°C), increasing one log count in three days. They exhibited slow acidification capacity, despite the increased production of lactic acid displayed by some strains after 24h. Bacteriocin activity was only detected in the whey of fresh cheese inoculated with two Enterococcus strains, but all cheeses made with bacteriocin-producing strains inhibited L. monocytogenes growth in the agar diffusion bioassay. No significant differences were found in overall sensory evaluation made by a non-trained panel of 50–52 tasters using the isolates as adjunct culture in fresh cheese, with the exception of one Enterococcus strain. To test the effect of in situ bacteriocin production against L. monocytogenes, fresh cheese was made from pasteurized cows' milk inoculated with bacteriocin-producing LAB and artificially contaminated with approximately 106 CFU/mL of L. monocytogenes. The numbers of L. monocytogenes were monitored during storage of fresh cheese at refrigeration temperature (4°C) for up to 15days. All strains controlled the growth of L. monocytogenes, although some Enterococcus were more effective in reducing the pathogen counts. After 7days, this reduction was of approximately 4 log units compared to the positive control. In comparison, an increase of 4logCFU/mL in pathogen numbers was detected over the same period, in the absence of bacteriocin-producing LAB. The combination of two bacteriocin producing Enterococcus sp. optimized the reduction of L. monocytogenes counts in fresh cheese, reducing by approximately 5logunits after 7days. The present work demonstrates that using bacteriocin-producing strains in the manufacture of fresh cheese might contribute to preventing the growth of undesirable pathogenic bacteria such as L. monocytogenes. A blend of two strains demonstrated great potential as a protective culture for the cheese making process.


      PubDate: 2014-09-16T19:21:42Z
       
  • Genetic diversity of FLO1 and FLO5 genes in wine flocculent Saccharomyces
           cerevisiae strains
    • Abstract: Publication date: 17 November 2014
      Source:International Journal of Food Microbiology, Volume 191
      Author(s): Rosanna Tofalo , Giorgia Perpetuini , Paola Di Gianvito , Maria Schirone , Aldo Corsetti , Giovanna Suzzi
      Twenty-eight flocculent wine strains were tested for adhesion and flocculation phenotypic variability. Moreover, the expression patterns of the main genes involved in flocculation (FLO1, FLO5 and FLO8) were studied both in synthetic medium and in presence of ethanol stress. Molecular identification and typing were achieved by PCR-RFLP of the 5.8S ITS rRNA region and microsatellite PCR fingerprinting, respectively. All isolates belong to Saccharomyces cerevisiae species. The analysis of microsatellites highlighted the intraspecific genetic diversity of flocculent wine S. cerevisiae strains allowing obtaining strain-specific profiles. Moreover, strains were characterized on the basis of adhesive properties. A wide biodiversity was observed even if none of the tested strains were able to form biofilms (or ‘mats’), or to adhere to polystyrene. Moreover, genetic diversity of FLO1 and FLO5 flocculating genes was determined by PCR. Genetic diversity was detected for both genes, but a relationship with the flocculation degree was not found. So, the expression patterns of FLO1, FLO5 and FLO8 genes was investigated in a synthetic medium and a relationship between the expression of FLO5 gene and the flocculation capacity was established. To study the expression of FLO1, FLO5 and FLO8 genes in floc formation and ethanol stress resistance qRT-PCR was carried out and also in this case strains with flocculent capacity showed higher levels of FLO5 gene expression. This study confirmed the diversity of flocculation phenotype and genotype in wine yeasts. Moreover, the importance of FLO5 gene in development of high flocculent characteristic of wine yeasts was highlighted. The obtained collection of S. cerevisiae flocculent wine strains could be useful to study the relationship between the genetic variation and flocculation phenotype in wine yeasts.


      PubDate: 2014-09-16T19:21:42Z
       
  • Exploring the diversity of extremely halophilic archaea in food-grade
           salts
    • Abstract: Publication date: 17 November 2014
      Source:International Journal of Food Microbiology, Volume 191
      Author(s): Olivier Henriet , Jeanne Fourmentin , Bruno Delincé , Jacques Mahillon
      Salting is one of the oldest means of food preservation: adding salt decreases water activity and inhibits microbial development. However, salt is also a source of living bacteria and archaea. The occurrence and diversity of viable archaea in this extreme environment were assessed in 26 food-grade salts from worldwide origin by cultivation on four culture media. Additionally, metagenomic analysis of 16S rRNA gene was performed on nine salts. Viable archaea were observed in 14 salts and colony counts reached more than 105 CFU per gram in three salts. All archaeal isolates identified by 16S rRNA gene sequencing belonged to the Halobacteriaceae family and were related to 17 distinct genera among which Haloarcula, Halobacterium and Halorubrum were the most represented. High-throughput sequencing generated extremely different profiles for each salt. Four of them contained a single major genus (Halorubrum, Halonotius or Haloarcula) while the others had three or more genera of similar occurrence. The number of distinct genera per salt ranged from 21 to 27. Halorubrum had a significant contribution to the archaeal diversity in seven salts; this correlates with its frequent occurrence in crystallization ponds. On the contrary, Haloquadratum walsbyi, the halophilic archaea most commonly found in solar salterns, was a minor actor of the food-grade salt diversity. Our results indicate that the occurrence and diversity of viable halophilic archaea in salt can be important, while their fate in the gastrointestinal tract after ingestion remains largely unknown.


      PubDate: 2014-09-16T19:21:42Z
       
  • Membrane lipid composition and stress/virulence related gene expression of
           Salmonella Enteritidis cells adapted to lactic acid and trisodium
           phosphate and their resistance to lethal heat and acid stress
    • Abstract: Publication date: 17 November 2014
      Source:International Journal of Food Microbiology, Volume 191
      Author(s): Yishan Yang , Mellissa Irlianti Kadim , Wei Jie Khoo , Qianwang Zheng , Magdiel Inggrid Setyawati , Yu-Jin Shin , Seung-Cheol Lee , Hyun-Gyun Yuk
      This study evaluated the acid and heat resistance of Salmonella Enteritidis in simulated gastric fluid (pH2.0) and during thermal treatment (54–60°C), respectively, after adaptation to lactic acid (LA) or trisodium phosphate (TSP) at various pHs (pH5.3–9.0). The changes in membrane lipid composition and expression levels of RpoS and RpoH were examined to elucidate their roles in bacterial stress resistance. Transcriptional profile of several virulence-related genes was also analyzed. Results showed that LA-adapted cells at pH5.3 and 6.3 had higher acid and heat resistance than control cells and cells adapted to TSP at pH8.3 and 9.0. LA-adapted cells had the lowest ratio of unsaturated to saturated fatty acids, indicating that they might possess a less fluid membrane. It was observed that the expression levels of RpoH and RpoS were upregulated in TSP-adapted cells but not in LA-adapted cells. Thus, these results indicate that the increased acid and heat resistance of LA-adapted S. Enteritidis was possibly due to the decreased membrane fluidity instead of the upregulation of RpoS and RpoH. About 6.0, 2.1, and 2.46-fold upregulation of spvR, avrA, and hilA were observed in cells adapted to TSP at pH9.0, except sefA that had its highest expression level in the control cells, indicating that the expression of these virulence genes highly depends on environmental conditions. This is the first study to show that the alteration in the cytoplasmic membrane rather than RpoS and RpoH plays a more crucial role in conferring greater acid and heat resistance on LA-adapted S. Enteritidis, thus providing a better understanding on the bacterial stress response to acidic conditions.


      PubDate: 2014-09-16T19:21:42Z
       
  • Applicability of a Lactobacillus amylovorus strain as co-culture for
           natural folate bio-enrichment of fermented milk
    • Abstract: Publication date: 17 November 2014
      Source:International Journal of Food Microbiology, Volume 191
      Author(s): Jonathan Emiliano Laiño , Marianela Juarez del Valle , Graciela Savoy de Giori , Jean Guy Joseph LeBlanc
      The ability of 55 strains from different Lactobacillus species to produce folate was investigated. In order to evaluate folic acid productivity, lactobacilli were cultivated in the folate-free culture medium (FACM). Most of the tested strains needed folate for growth. The production and the extent of vitamin accumulation were distinctive features of individual strains. Lactobacillus amylovorus CRL887 was selected for further studies because of its ability to produce significantly higher concentrations of vitamin (81.2±5.4μg/L). The safety of this newly identified folate producing strain was evaluated through healthy experimental mice. No bacterial translocation was detected in liver and spleen after consumption of CRL887 during 7 days and no undesirable side effects were observed in the animals that received this strain. This strain in co-culture with previously selected folate producing starter cultures (Lactobacillus bulgaricus CRL871, and Streptococcus thermophilus CRL803 and CRL415) yielded a yogurt containing high folate concentrations (263.1±2.4μg/L); a single portion of which would provide 15% of the recommended dietary allowance. This is the first report where a Lactobacillus amylovorus strain was successfully used as co-culture for natural folate bio-enrichment of fermented milk.


      PubDate: 2014-09-16T19:21:42Z
       
  • Combined effects of benomyl and environmental factors on growth and
           expression of the fumonisin biosynthetic genes FUM1 and FUM19 by Fusarium
           verticillioides
    • Abstract: Publication date: 17 November 2014
      Source:International Journal of Food Microbiology, Volume 191
      Author(s): A. Cruz , P. Marín , N. Magan , M.T. González-Jaén
      Fusarium verticillioides is predominantly responsible of fumonisin contamination of maize and other cereals in Mediterranean climatic regions. This study examined the interaction of the fungicide benomyl, at ED50 and ED90 concentrations (effective doses of benomyl to reduce growth by 50% and 90%, respectively), with a range of temperatures (20–35°C) and water potentials (−0.7, −2.8 and −7.0MPa) compatible with current and foreseen climate change scenarios for these regions on growth and fumonisin biosynthesis in in vitro assays. The expression of fumonisin biosynthetic genes (FUM1 and FUM19) was quantified by real time RT-PCR. FUM1 encodes a polyketide synthase and FUM19 an ABC-type transporter, located both in the fumonisin biosynthetic cluster. The ED50 and ED90 concentrations obtained at 25°C were 0.93mg/L and 3.30mg/L, respectively. Benomyl affected growth and fumonisin gene expression differently but it generally reduced fungal growth and fumonisin biosynthesis and both were significantly affected by temperature and water potential. This indicated that efficacy of benomyl might be compromised at certain conditions, although at similar or lower levels than other fungicides tested. Both fumonisin biosynthetic genes had similar expression patterns in all treatments and their correlation was positive and significant. The results suggested that Mediterranean climatic scenarios might suffer an additional negative impact of climate change by reducing the efficacy of antifungals used to control pathogens and toxigenic fungi.


      PubDate: 2014-09-16T19:21:42Z
       
  • Monitoring of Saccharomyces cerevisiae, Hanseniaspora uvarum, and
           Starmerella bacillaris (synonym Candida zemplinina) populations during
           alcoholic fermentation by fluorescence in situ hybridization
    • Abstract: Publication date: 17 November 2014
      Source:International Journal of Food Microbiology, Volume 191
      Author(s): Chunxiao Wang , Braulio Esteve-Zarzoso , Albert Mas
      Various molecular approaches have been applied as culture-independent techniques to monitor wine fermentations over the last decade. Among them, those based on RNA detection have been widely used for yeast cell detection, assuming that RNA only exists in live cells. Fluorescence in situ hybridization (FISH) targeting intracellular rRNA is considered a promising technique for the investigation of wine ecology. For the present study, we applied the FISH technique in combination with epifluorescence microscopy and flow cytometry to directly quantify populations of Saccharomyces cerevisiae, Hanseniaspora uvarum, and Starmerella bacillaris during alcoholic fermentations. A new specific probe that hybridizes with eight species of Hanseniaspora genus and a second probe specific for Starm. bacillaris were designed, and the conditions for their application to pure cultures, mixed cultures, and wine samples were optimized. Single and mixed fermentations were performed with natural, concentrated must at two different temperatures, 15°C and 25°C. The population dynamics revealed that the Sacch. cerevisiae population increased to 107–108 cells/ml during all fermentations, whereas H. uvarum and Starm. bacillaris tended to increase in single fermentations but remained at levels similar to their inoculations at 106 cells/ml in mixed fermentations. Temperature mainly affected the fermentation duration (slower at the lower temperature) but did not affect the population sizes of the different species. The use of these probes in natural wine fermentations has been validated.


      PubDate: 2014-09-16T19:21:42Z
       
  • Variable flocculation profiles of yeast strains isolated from cachaça
           distilleries
    • Abstract: Publication date: 3 November 2014
      Source:International Journal of Food Microbiology, Volume 190
      Author(s): Florencia Alvarez , Lygia Fátima da Mata Correa , Thalita Macedo Araújo , Bruno Eduardo Fernandes Mota , Luís Eduardo F. Ribeiro da Conceição , Ieso de Miranda Castro , Rogelio Lopes Brandão
      In cachaça production, the use of yeast cells as starters with predictable flocculation behavior facilitates the cell recovery at the end of each fermentation cycle. Therefore, the aim of this work was to explain the behavior of cachaça yeast strains in fermentation vats containing sugarcane through the determination of biochemical and molecular parameters associated with flocculation phenotypes. By analyzing thirteen cachaça yeast strains isolated from different distilleries, our results demonstrated that neither classic biochemical measurements (e.g., percentage of flocculation, EDTA sensitivity, cell surface hydrophobicity, and sugar residues on the cell wall) nor modern molecular approaches, such as polymerase chain reaction (PCR) and real-time PCR (q-PCR), were sufficient to distinctly classify the cachaça yeast strains according to their flocculation behavior. It seems that flocculation is indeed a strain-specific phenomenon that is difficult to explain and/or categorize by the available methodologies.


      PubDate: 2014-09-11T19:18:51Z
       
  • Genetic diversity and dynamics of bacterial and yeast strains associated
           to Spanish-style green table-olive fermentations in large manufacturing
           companies
    • Abstract: Publication date: 3 November 2014
      Source:International Journal of Food Microbiology, Volume 190
      Author(s): Helena Lucena-Padrós , Belén Caballero-Guerrero , Antonio Maldonado-Barragán , José Luis Ruiz-Barba
      We have genotyped a total of 1045 microbial isolates obtained along the fermentation time of Spanish-style green table olives from the fermentation yards (patios) of two large manufacturing companies in the Province of Sevilla, south of Spain. Genotyping was carried out using RAPD-PCR fingerprinting. In general, isolates clustered well into the relevant phylogenetic dendrograms, forming separate groups in accordance to their species adscription. We could identify which bacterial and yeast genotypes (strains) persisted throughout the fermentation at each patio. Also, which of them were more adapted to any of the three stages, i.e. initial, middle and final, described for this food fermentation. A number of genotypes were found to be shared by both patios. Fifty seven of these belonged to five different bacterial species, i.e. Lactobacillus pentosus, Lactobacillus paracollinoides/collinoides, Lactobacillus rapi, Pediococcus ethanolidurans and Staphylococcus sp., although most of them (51) belonged to L. pentosus. Four yeast genotypes were also shared, belonging to the species Candida thaimueangensis, Saccharomyces cerevisiae and Hanseniaspora sp. Two genotypes of L. pentosus were found to be grouped with those of two strains used in commercially available starter cultures, one of them bacteriocinogenic, which were used up to three years before this study in these patios, demonstrating the persistence of selected strains in this environment. Biodiversity was assessed though different indexes, including richness, diversity and dominance. A statistically significant decrease in biodiversity between the initial and final stages of the fermentation was found in both patios. However, values of biodiversity indexes in the fermenters were very similar, and no significant differences were found in the total biodiversity between both patios. This study allowed us to identify a range of well adapted strains (genotypes), especially those belonging to the lactic acid bacteria, which could be useful to improve safety and quality of table olive fermentations.


      PubDate: 2014-09-11T19:18:51Z
       
  • Microbial succession of grass carp (Ctenopharyngodon idellus) filets
           during storage at 4°C and its contribution to biogenic amines'
           formation
    • Abstract: Publication date: 3 November 2014
      Source:International Journal of Food Microbiology, Volume 190
      Author(s): Hang Wang , Yongkang Luo , Heping Huang , Qian Xu
      Investigation on the microbial succession of grass carp filets during storage at 4°C was carried out. For identification, 16S rRNA genes of the isolated pure strains were sequenced and analyzed. Acinetobacter was dominant in fresh grass carp. Species from the genera Brevundimonas, Empedobacter, Pseudomonas, Microbacterium, Flavobacterium, Moraxella, Shewanella and Soonwooa were also detected at the initial day. The communities were dominated by Aeromonas and Acinetobacter after 6days. Aeromonas followed by Pseudomonas was the predominant genera at the end of shelf-life of grass carp, while other genera such as Shewanella, Acinetobacter, Flavobacteriaceae and Psychrobacter were present in smaller numbers. We investigated biogenic amines' (BAs) production by six strains isolated from spoiled grass carp filets. Shewanella putrefaciens showed significantly higher abilities to produce putrescine, than those from other genera. Aeromonas veronii revealed a strong ability to produce putrescine and cadaverine. However, Pseudomonas and Acinetobacter showed little ability to produce BAs.


      PubDate: 2014-09-11T19:18:51Z
       
  • African fermented foods and probiotics
    • Abstract: Publication date: 3 November 2014
      Source:International Journal of Food Microbiology, Volume 190
      Author(s): Charles M.A.P. Franz , Melanie Huch , Julius Maina Mathara , Hikmate Abriouel , Nabil Benomar , Gregor Reid , Antonio Galvez , Wilhelm H. Holzapfel
      Africa has an age old history of production of traditional fermented foods and is perhaps the continent with the richest variety of lactic acid fermented foods. These foods have a large impact on the nutrition, health and socio-economy of the people of the continent, often plagued by war, drought, famine and disease. Sub-Saharan Africa is the world's region with the highest percentage of chronically malnourished people and high child mortality. Further developing of traditional fermented foods with added probiotic health features would be an important contribution towards reaching the UN Millennium Development Goals of eradication of poverty and hunger, reduction in child mortality rates and improvement of maternal health. Specific probiotic strains with documented health benefits are sparsely available in Africa and not affordable to the majority of the population. Furthermore, they are not used in food fermentations. If such probiotic products could be developed especially for household food preparation, such as cereal or milk foods, it could make a profound impact on the health and well-being of adults and children. Suitable strains need to be chosen and efforts are needed to produce strains to make products which will be available for clinical studies. This can gauge the impact of probiotics on consumers' nutrition and health, and increase the number of people who can benefit.


      PubDate: 2014-09-11T19:18:51Z
       
  • Multilocus variable-number of tandem repeat analysis (MLVA) for
           Clostridium tyrobutyricum strains isolated from cheese production
           environment
    • Abstract: Publication date: 3 November 2014
      Source:International Journal of Food Microbiology, Volume 190
      Author(s): Masaharu Nishihara , Hajime Takahashi , Tomoko Sudo , Daisuke Kyoi , Toshio Kawahara , Yoshihiro Ikeuchi , Takashi Fujita , Takashi Kuda , Bon Kimura , Shuichi Yanahira
      Clostridium tyrobutyricum is a gram-positive spore-forming anaerobe that is considered as the main causative agent for late blowing in cheese due to butyric acid fermentation. In this study, multilocus variable-number of tandem repeat (VNTR) analysis (MLVA) for C. tyrobutyricum was developed to identify the source of contamination by C. tyrobutyricum spores in the cheese production environment. For each contig constructed from the results of a whole genome draft sequence of C. tyrobutyricum JCM11008T based on next-generation sequencing, VNTR loci that were effective for typing were searched using the Tandem Repeat Finder program. Five VNTR loci were amplified by polymerase chain reaction (PCR) to determine their number of repeats by sequencing, and MLVA was conducted. 25 strains of C. tyrobutyricum isolated from the environment, raw milk, and silage were classified into 18 MLVA types (DI=0.963). Of the C. tyrobutyricum strains isolated from raw milk, natural cheese, and blown processed cheese, strains with identical MLVA type were detected, which suggested that these strains might have shifted from natural cheese to blown processed cheese. MLVA could be an effective tool for monitoring contamination of natural cheese with C. tyrobutyricum in the processed cheese production environment because of its high discriminability, thereby allowing the analyst to trace the source of contamination.


      PubDate: 2014-09-06T19:11:50Z
       
  • Phytic acid degrading lactic acid bacteria in tef-injera fermentation
    • Abstract: Publication date: 3 November 2014
      Source:International Journal of Food Microbiology, Volume 190
      Author(s): Maren M. Fischer , Ines M. Egli , Isabelle Aeberli , Richard F. Hurrell , Leo Meile
      Ethiopian injera, a soft pancake, baked from fermented batter, is preferentially prepared from tef (Eragrostis tef) flour. The phytic acid (PA) content of tef is high and is only partly degraded during the fermentation step. PA chelates with iron and zinc in the human digestive tract and strongly inhibits their absorption. With the aim to formulate a starter culture that would substantially degrade PA during injera preparation, we assessed the potential of microorganisms isolated from Ethiopian household-tef fermentations to degrade PA. Lactic acid bacteria (LAB) were found to be among the dominating microorganisms. Seventy-six isolates from thirteen different tef fermentations were analyzed for phytase activity and thirteen different isolates of seven different species were detected to be positive in a phytase screening assay. In 20-mL model tef fermentations, out of these thirteen isolates, the use of Lactobacillus (L.) buchneri strain MF58 and Pediococcus pentosaceus strain MF35 resulted in lowest PA contents in the fermented tef of 41% and 42%, respectively of its initial content. In comparison 59% of PA remained when spontaneously fermented. Full scale tef fermentation (0.6L) and injera production using L. buchneri MF58 as culture additive decreased PA in cooked injera from 1.05 to 0.34±0.02g/100g, representing a degradation of 68% compared to 42% in injera from non-inoculated traditional fermentation. The visual appearance of the pancakes was similar. The final molar ratios of PA to iron of 4 and to zinc of 12 achieved with L. buchneri MF58 were decreased by ca. 50% compared to the traditional fermentation. In conclusion, selected LAB strains in tef fermentations can degrade PA, with L. buchneri MF58 displaying the highest PA degrading potential. The 68% PA degradation achieved by the application of L. buchneri MF58 would be expected to improve human zinc absorption from tef-injera, but further PA degradation is probably necessary if iron absorption has to be increased.


      PubDate: 2014-09-01T18:44:46Z
       
  • An educationally inspired illustration of two-dimensional Quantitative
           Microbiological Risk Assessment (QMRA) and sensitivity analysis
    • Abstract: Publication date: 3 November 2014
      Source:International Journal of Food Microbiology, Volume 190
      Author(s): G.A. Vásquez , P. Busschaert , L.U. Haberbeck , M. Uyttendaele , A.H. Geeraerd
      Quantitative Microbiological Risk Assessment (QMRA) is a structured methodology used to assess the risk involved by ingestion of a pathogen. It applies mathematical models combined with an accurate exploitation of data sets, represented by distributions and – in the case of two-dimensional Monte Carlo simulations – their hyperparameters. This research aims to highlight background information, assumptions and truncations of a two-dimensional QMRA and advanced sensitivity analysis. We believe that such a detailed listing is not always clearly presented in actual risk assessment studies, while it is essential to ensure reliable and realistic simulations and interpretations. As a case-study, we are considering the occurrence of listeriosis in smoked fish products in Belgium during the period 2008–2009, using two-dimensional Monte Carlo and two sensitivity analysis methods (Spearman correlation and Sobol sensitivity indices) to estimate the most relevant factors of the final risk estimate. A risk estimate of 0.018% per consumption of contaminated smoked fish by an immunocompromised person was obtained. The final estimate of listeriosis cases (23) is within the actual reported result obtained for the same period and for the same population. Variability on the final risk estimate is determined by the variability regarding (i) consumer refrigerator temperatures, (ii) the reference growth rate of L. monocytogenes, (iii) the minimum growth temperature of L. monocytogenes and (iv) consumer portion size. Variability regarding the initial contamination level of L. monocytogenes tends to appear as a determinant of risk variability only when the minimum growth temperature is not included in the sensitivity analysis; when it is included the impact regarding the variability on the initial contamination level of L. monocytogenes is disappearing. Uncertainty determinants of the final risk indicated the need of gathering more information on the reference growth rate and the minimum growth temperature of L. monocytogenes. Uncertainty in the dose–response relationship was not included in the analysis, hence the level of its influence cannot be assessed in the present research. Finally, a baseline global workflow for QMRA and sensitivity analysis is proposed.


      PubDate: 2014-09-01T18:44:46Z
       
  • Microbial communities in air and wine of a winery at two consecutive
           vintages
    • Abstract: Publication date: 3 November 2014
      Source:International Journal of Food Microbiology, Volume 190
      Author(s): Fátima Pérez-Martín , Susana Seseña , Mónica Fernández-González , María Arévalo , María Llanos Palop
      The aim of this study was to assess, both quantitatively and qualitatively, the populations of lactic acid bacteria (LAB) and yeasts in air and wine of a winery, in order to evaluate the possible exchange of microorganisms between them. Samples were taken in a winery located in Castilla-La Mancha (Spain) during the winemaking period of two consecutive vintages (2011 and 2012). The microbial composition was determined by using both a culture-dependent method and a culture-independent method, PCR-denaturing gradient gel electrophoresis (PCR-DGGE). In addition, genetic characterization of isolates from plates was carried out. A high diversity of species was detected in air and wine samples from both vintages. Leuconostoc mesenteroides was the predominant lactic acid bacteria in air from both vintages while Oenococcus oeni was the predominant in wine. Saccharomyces cerevisiae was the most frequently isolated yeast in both air and wine. Typing of O. oeni and S. cerevisiae isolates from air and wine samples showed the presence of coincident genotypes in both samples, that would confirm the exchange of microorganisms between the two environments, air and wine, and furthermore some of these genotypes were also found at samples taken at different vintages, indicating that they would remain in the winery. The results display the influence of the activity taking place in the winery and the moment of fermentation of the wines in tanks, on the microorganisms present in the air and the role of the air for the dispersal of microorganisms within the winery.


      PubDate: 2014-09-01T18:44:46Z
       
  • Bovicin HC5 and nisin reduce Staphylococcus aureus adhesion to polystyrene
           and change the hydrophobicity profile and Gibbs free energy of adhesion
    • Abstract: Publication date: 3 November 2014
      Source:International Journal of Food Microbiology, Volume 190
      Author(s): Natan de Jesus Pimentel-Filho , Mayra Carla de Freitas Martins , Guilherme Bicalho Nogueira , Hilário Cuquetto Mantovani , Maria Cristina Dantas Vanetti
      Staphylococcus aureus is an opportunistic pathogen often multidrug-resistant that not only causes a variety of human diseases, but also is able to survive on biotic and abiotic surfaces through biofilm communities. The best way to inhibit biofilm establishment is to prevent cell adhesion. In the present study, subinhibitory concentrations of the bacteriocins bovicin HC5 and nisin were tested for their capability to interfere with the adhesion of S. aureus to polystyrene. Subinhibitory dosages of the bacteriocins reduced cell adhesion and this occurred probably due to changes in the hydrophobicity of the bacterial cell and polystyrene surfaces. After treatment with bovicin HC5 and nisin, the surfaces became more hydrophilic and the free energy of adhesion (∆G adhesion) between bacteria and the polystyrene surface was unfavorable. The transcriptional level of selected genes was assessed by RT-qPCR approach, revealing that the bacteriocins affected the expression of some important biofilm associated genes (icaD, fnbA, and clfB) and rnaIII, which is involved in the quorum sensing mechanism. The conditioning of food-contact surfaces with bacteriocins can be an innovative and powerful strategy to prevent biofilms in the food industry. The results are relevant for food safety as they indicate that bovicin HC5 and nisin can inhibit bacterial adhesion and consequent biofilm establishment, since cell adhesion precedes biofilm formation.


      PubDate: 2014-09-01T18:44:46Z
       
  • Benzalkonium chloride and heavy-metal tolerance in Listeria monocytogenes
           from retail foods
    • Abstract: Publication date: 3 November 2014
      Source:International Journal of Food Microbiology, Volume 190
      Author(s): Dongyang Xu , Yanli Li , M. Shamim Hasan Zahid , Shinji Yamasaki , Lei Shi , Jian-rong Li , He Yan
      Phenotypic and genotypic tolerance in 71 Listeria monocytogenes isolates from different varieties of foods to benzalkonium chloride (BC) and cadmium were investigated by susceptibility test and molecular methods. To investigate the role of efflux pumps in BC tolerance, reserpine, an efflux pump inhibitor, was added to the BC tolerant strains. Tolerance to BC and cadmium were 26.8% (19/71) and 49.3% (35/71) respectively. Strains with BC tolerance were significantly more frequent among those of serotype 4b (100%, 6/6) than among those of serotype 1/2a (or 3a) (13.5%, 5/37), which represent the predominant number of strains (52.1%, 37/71). Tolerance to cadmium was encountered among 62.2% (23/37) and 50.0% (3/6) of the serotype 1/2a (or 3a) and 4b strains, respectively, and among 19.0% (4/21) of the strains of the serotype 1/2c. All of the 10 (14.1%) isolates found to be BC and cadmium co-tolerance were isolated from raw meat or quick-frozen food made of wheat flour and rice. Five multi-drug resistant strains were tolerant to cadmium as well. Among 71 isolates examined, one contained qacA and three contained qacEΔ1-sul. To the best of our knowledge, this is the first detection of qacA and qacEΔ1-sul in L. monocytogenes, an indication of the possible horizontal transfer of the two genes. Addition of reserpine to the tolerant strains resulted in the loss of tolerance among seven out of 19 BC strains, suggesting a certain role the efflux pump played in mediating BC tolerance. Of the three distinct cadA types known to date in L. monocytogenes, the cadA1 and cadA2 genes were detected among 24 (33.8%) and three (4.2%) isolates respectively. The presence of cadA1 and cadA2 largely corresponded to the susceptibility phenotype. A subset (9/35 [25.7%]) of the cadmium-tolerant isolates lacked the known cadmium resistance determinants. These findings suggest that food products could act as a reservoir for L. monocytogenes harboring tolerance to BC and cadmium and will further our understanding of the adaptations of this organism to these two compounds.


      PubDate: 2014-09-01T18:44:46Z
       
  • Control of tyramine and histamine accumulation by lactic acid bacteria
           using bacteriocin forming lactococci
    • Abstract: Publication date: 3 November 2014
      Source:International Journal of Food Microbiology, Volume 190
      Author(s): Giulia Tabanelli , Chiara Montanari , Eleonora Bargossi , Rosalba Lanciotti , Veronica Gatto , Giovanna Felis , Sandra Torriani , Fausto Gardini
      The aim of this study was to evaluate the competitive effects of three bacteriocin producing strains of Lactococcus lactis subsp. lactis against two aminobiogenic lactic acid bacteria, i.e. the tyramine producing strain Enterococcus faecalis EF37 and the histamine producing strain Streptococcus thermophilus PRI60, inoculated at different initial concentrations (from 2 to 6logcfu/ml). The results showed that the three L. lactis subsp. lactis strains were able to produce bacteriocins: in particular, L. lactis subsp. lactis VR84 and EG46 produced, respectively, nisin Z and lacticin 481, while for the strains CG27 the bacteriocin has not been yet identified, even if its peptidic nature has been demonstrated. The co-culture of E. faecalis EF37 in combination with lactococci significantly reduced the growth potential of this aminobiogenic strain, both in terms of growth rate and maximum cell concentration, depending on the initial inoculum level of E. faecalis. Tyramine accumulation was strongly reduced when E. faecalis EF37 was inoculated at 2logcfu/ml and, to a lesser extent, at 3logcfu/ml, as a result of a lower cell load of the aminobiogenic strain. All the lactococci were more efficient in inhibiting streptococci in comparison with E. faecalis EF37; in particular, L. lactis subsp. lactis VR84 induced the death of S. thermophilus PRI60 and allowed the detection of histamine traces only at higher streptococci inoculum levels (5–6logcfu/ml). The other two lactococcal strains did not show a lethal action against S. thermophilus PRI60, but were able to reduce its growth extent and histamine accumulation, even if L. lactis subsp. lactis EG46 was less effective when the initial streptococci concentration was 5 and 6logcfu/ml. This preliminary study has clarified some aspects regarding the ratio between bacteriocinogenic strains and aminobiogenic strains with respect to the possibility to accumulate BA and has also showed that different bacteriocins can have different effects on BA production on the same strain. This knowledge is essentially aimed to use bacteriocinogenic lactococci as a predictable strategy against aminobiogenic bacteria present in cheese or other fermented foods.


      PubDate: 2014-09-01T18:44:46Z
       
  • Removal of Salmonella enterica Enteritidis and Escherichia coli from green
           peppers and melons by ultrasound and organic acids
    • Abstract: Publication date: 3 November 2014
      Source:International Journal of Food Microbiology, Volume 190
      Author(s): Jackline Freitas Brilhante de São José , Hiasmyne Silva de Medeiros , Patrícia Campos Bernardes , Nélio José de Andrade
      The aim of this study was to evaluate the effectiveness of ultrasound treatment combined with organic acids in the decontamination step for green peppers and melons. The influence of the surface roughness of the peppers and melons on bacterial adhesion was evaluated, as measured using a profilometer. The adhesion of Salmonella enterica serovar Enteritidis and Escherichia coli to the green pepper and melon surfaces was also evaluated by measuring the hydrophobicity of the microorganisms and the surfaces. The bacteria that adhered to the surface of green peppers and melons was quantified by plate count and visualized by scanning electron microscopy. In addition, the efficiency of ultrasound and organic acids to remove bacteria from the pepper and melon surfaces was examined. The average roughness (R a) of the green peppers (13.0±2.7nm) was significantly different (p >0.05) from the melons (33.5±7.9nm). Adherence of S. Enteritidis and E. coli are thermodynamically unfavorable for both surfaces studied (∆G adhesion >0). Despite these data, good adhesion occurred on both surfaces. The number of bacteria on green pepper slices was 7.3 and 7.0logCFU/cm2 for E. coli and S. enterica Enteritidis, respectively. For melon surfaces, the number of bacteria was 7.0 and 6.9logCFU/cm2 for E. coli and S. Enteritidis, respectively. The greater adherence of both bacteria on the green peppers can be explained by its hydrophobic surface; the hydrophilic surfaces of melons resulted in lower adherence. These results suggest that the adhesion observed in this experiment is a multifactorial process. Among the treatments evaluated for green peppers, a higher removal of pathogens was observed after use of a combination of ultrasound and 1% lactic acid; this treatment reduced E. coli and Salmonella by 2.9 and 2.8logCFU/cm2, respectively. For melons, the combination of ultrasound and lactic acid showed a reduction of 2.5 and 3.1logCFU/cm2 for E. coli and S. Enteritidis, respectively. These results indicate that it is possible to replace the chlorinated compounds that are commonly used to sanitize fruits and vegetables. These results confirm that ultrasound, an emerging technology for food processing applications, could enhance the microbial safety of fresh produce.


      PubDate: 2014-09-01T18:44:46Z
       
 
 
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