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Biodegradation
Journal Prestige (SJR): 0.876  Citation Impact (citeScore): 2 Number of Followers: 2  Hybrid journal (It can contain Open Access articles)ISSN (Print) 1572-9729 - ISSN (Online) 0923-9820 Published by Springer-Verlag  [2658 journals]
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- Biodegradation of 4-hydroxybenzoic acid by Acinetobacter johnsonii FZ-5
and Klebsiella oxytoca FZ-8 under anaerobic conditions-
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Abstract: 4-Hydroxybenzoic acid (4-HBA) is a common organic compound that is prevalent in the environment, and the persistence of 4-HBA residues results in exertion of pollution-related detrimental effects. Bioremediation is an effective method for the removal of 4-HBA from the environment. In this study, two bacterial strains FZ-5 and FZ-8 capable of utilizing 4-HBA as the sole carbon and energy source under anaerobic conditions were isolated from marine sediment samples. Phylogenetic analysis identified the two strains FZ-5 and FZ-8 as Acinetobacter johnsonii and Klebsiella oxytoca, respectively. The strains FZ-5 and FZ-8 degraded 2000 mg·L−1 4-HBA in 72 h with degradation rates of 71.04% and 80.10%, respectively. The optimum culture conditions for degradation by the strains and crude enzymes were also investigated. The strains FZ-5 and FZ-8 also exhibited the ability to degrade other lignin-derived compounds, such as protocatechuic acid, cinnamic acid, and vanillic acid. Immobilization of the two strains showed that they could be used for the bioremediation of 4-HBA in an aqueous environment. Soils inoculated with the strains FZ-5 and FZ-8 showed higher degradation of 4-HBA than the uninoculated soil, and the strains could survive efficiently in anaerobic soil. This is the first report of 4-HBA-degrading bacteria, belonging to the two genera, which showed degradation ability under anaerobic conditions. This study expound the strains could efficiently degrade 4-HBA in anaerobic soil and will help in the development of 4-HBA anaerobic bioremediation systems.
PubDate: 2021-10-05
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- RETRACTED ARTICLE: Role of UV photolysis in accelerating the
biodegradation of 2,4,6-TCP-
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Abstract: The Editor in Chief and the authors have retracted this article because of multiple errors in the data that undermine the conclusions of the study. Bruce E Rittman agreed to this retraction wording. Yanqing Wu stated on behalf of all remaining authors that they agree to this retraction. The online version of this article contains the full text of the retracted article as Supplementary Information.
PubDate: 2021-10-01
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- Assessment of polyethylene degradation by biosurfactant producing
ligninolytic bacterium-
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Abstract: Accumulation of plastic waste has become an environmental threat and a global problem. In this research, polyethylene degrading ligninolytic bacteria were isolated from plastic waste polluted soil. Two bacterial isolates, namely PE2 and PE3 have been obtained from the soil samples. Polyethylene degrading ability of the isolates has been assessed individually in a synthetic media containing polyethylene as a carbon source. The results indicated that maximum weight reduction of polyethylene (6.68%) was found in PE3 inoculated media after thirty days of incubation. Fourier Transform Infrared Spectroscopic results showed the appearance of carbonyl peaks. 16S rRNA gene sequencing studies revealed that the potential isolate PE3 belongs to the genus Bacillus and it was named Bacillus sp. strain PE3. From the scanning electron microscopic results, it is inferred that Bacillus sp. strain PE3 could colonize on the polyethylene surface and form a biofilm. Besides, the viable Bacillus sp. strain PE3 on polyethylene surface was confirmed by fluorescence microscopic analysis. Alkanes and fatty acids were identified in the degraded products by gas chromatography-mass spectrometer analysis. From the results of native polyacrylamide gel electrophoresis, the activities of laccase and lignin peroxidase were noticed. Furthermore, extracellular production of biosurfactant has been observed in the Bacillus sp. strain PE3 inoculated mineral salt media and synthetic media with glucose and polyethylene as the carbon source respectively. The characterization studies of crude biosurfactant have confirmed that lipopeptide nature biosurfactant. The present study demonstrates that the ligninolytic enzymes laccase, lignin peroxidase, and lipopeptide type biosurfactant are produced by Bacillus sp. strain PE3 in the media with polyethylene as a carbon source. Graphic abstract
PubDate: 2021-10-01
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- Functional interplay between plastic polymers and microbes: a
comprehensive review-
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Abstract: Escalated production of plastic, their worldwide distribution and persistent nature finally results into their environmental accumulation causing severe threats to the ecological environment and biotic health. Thus, development of suitable measurements for environmental remediation of plastic may be an urgent issue in this plastic age. Some recent reviews have categorized the microbial species able to degrade different plastic polymers and the different factors effecting bio-degradation of plastic are poorly understood. This review comprehensively discusses bio-degradation of traditional and biodegradable plastic polymers both in natural and biological environment (gut microbes and fungi) to understand different factors regulating their degradation, and also shows how degradation of plastic polymers under abiotic factors influence subsequent biological degradation. Different physicochemical modifications like - breaking large polymers into small fragments by pre-treatment, functional groups enrichment, identifying potent microbial species (consortia) and engineering microbial enzymes might be crucial for bio-degradations of plastic. Effects of micro/nanoplastic and other chemical intermediates, formed during the bio-degradation of plastic, on species composition, abundance, growth, metabolism and enzymatic systems of microbes involved in the bio-degradation of plastic should be determined in future research.
PubDate: 2021-10-01
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- Efficiencies of selected biotreatments for the remediation of PAH in
diluted bitumen contaminated soil microcosms-
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Abstract: Unconventional oils such as diluted bitumen from oil sands differs from most of conventional oils in terms of physiochemical properties and PAHs composition. This raises concerns regarding the effectiveness of current remediation strategies and protocols originally developed for conventional oil. Here we evaluated the efficiency of different biotreatment approaches, such as fungi inoculation (bioaugmentation), sludge addition (bioaugmentation/biostimulation), perennial grasses plantation (phytoremediation) and their combinations as well as natural attenuation (as control condition), for the remediation of soil contaminated by synthetic crude oil (a product of diluted bitumen) in laboratory microcosms. We specifically monitored the PAHs loss percentage (alkylated PAHs and unsubstituted 16 EPA Priority PAHs), the residue of PAHs and evaluated the ecotoxicity of soil after treatment. All treatments were highly efficient with more than ~ 80% of ∑PAHs loss after 60 days. Distinctive loss efficiencies between light PAHs (≤ 3 rings, ~ 96% average loss) and heavy PAHs (4–6 rings, ~ 29% average loss) were observed. The lowest average PAHs residue (0.10 ± 0.02 mg·kg−1, for an initial concentration of 0.29 ± 0.12 mg·kg−1) was achieved with the “sludge—plants (grasses)” combination. Sludge addition was the only treatment that achieved significantly lower ecotoxicity (3% ± 4% of growth inhibition of L. sativa) than the control (natural attenuation, 13% ± 4% of inhibition). Sludge addition, grasses plantation and “sludge—fungi combination” treatments could result in lower PAH exposure (than other treatments) in post-treated soil when using the Canadian Soil Quality Guidelines for the protection of environmental and human health for potentially carcinogenic and other PAHs.
PubDate: 2021-10-01
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- Temperature-induced difference in microbial characterizations accounts for
the fluctuation of sequencing batch biofilm reactor performance-
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Abstract: Generally, the purification performance of bioreactors could be influenced by temperature variation via shaping different microbial communities. However, the underlying mechanisms remain largely unknown. Here, the variation trends of microbial communities in three sequencing batch biofilm reactors (SBBRs) under four different temperatures (15, 20, 25, 30 °C) were compared. It was found that temperature increment led to an obvious enhancement in nutrient removal which was mainly occurred in the aerobic section. Meanwhile, distinct differences in dominant microbial communities or autotrophic nitrifiers were also observed. The performance of the SBBR reactors was closely associated with nitrifier communities since the treated wastewater was characterized by a severe lack of carbon sources (mean effluent COD ≤ 14.4 mg/L). Spearman correlation unraveled that: most of the differentiated microbes as well as the dominant potential functions were strongly associated with nutrient removal, indicating the temperature-induced difference in microbial community well explained the distinction in purification performance.
PubDate: 2021-10-01
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- Sediments in the mangrove areas contribute to the removal of endocrine
disrupting chemicals in coastal sediments of Macau SAR, China, and harbour
microbial communities capable of degrading E2, EE2, BPA and BPS-
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Abstract: The occurrence of endocrine disrupting chemicals (EDCs) is a major issue for marine and coastal environments in the proximity of urban areas. The occurrence of EDCs in the Pearl River Delta region is well documented but specific data related to Macao is unavailable. The levels of bisphenol-A (BPA), estrone (E1), 17α-estradiol (αE2), 17β-estradiol (E2), estriol (E3), and 17α-ethynylestradiol (EE2) were measured in sediment samples collected along the coastline of Macao. BPA was found in all 45 collected samples with lower BPA concentrations associated to the presence of mangrove trees. Biodegradation assays were performed to evaluate the capacity of the microbial communities of the surveyed ecosystems to degrade BPA and its analogue BPS. Using sediments collected at a WWTP discharge point as inoculum, at a concentration of 2 mg l−1 complete removal of BPA was observed within 6 days, whereas for the same concentration BPS removal was of 95% after 10 days, which is particularly interesting since this compound is considered recalcitrant to biodegradation and likely to accumulate in the environment. Supplementation with BPA improved the degradation of bisphenol-S (BPS). Aiming at the isolation of EDCs-degrading bacteria, enrichments were established with sediments supplied with BPA, BPS, E2 and EE2, which led to the isolation of a bacterial strain, identified as Rhodoccoccus sp. ED55, able to degrade the four compounds at different extents. The isolated strain represents a valuable candidate for bioremediation of contaminated soils and waters.
PubDate: 2021-10-01
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- Increasing electron donor concentration does not accelerate complete
microbial reductive dechlorination in contaminated sediment with native
organic carbon-
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Abstract: Experiments with Fe(III)-rich, chloroethene-contaminated sediment demonstrated that trichloroethylene (TCE) and vinyl chloride (VC) were completely reduced to ethene regardless of whether electron donor(s) were added at 1 × stoichiometry or 10 × stoichiometry relative to all-electron acceptors. Unamended controls uniformly reduced TCE to ethene with a mean time to complete dechlorination (operationally defined as the presence of stoichiometric ethene production) of 79 days. Adding 1 × and 10 × acetate hindered the rate and extent of TCE and VC reduction relative to unamended controls, with several only partially reduced when the experiments were terminated. Adding high molecular mass (soybean oil derivative) substrates did not increase microbial reductive dechlorination relative to unamended incubations, and in many cases, hindered microbial dechlorination in favor of methanogenesis. The mean time to complete dechlorination was comparable between low (× 1) and high (× 10) electron donor concentration for all lipid-based electron donors tested. Those tested included Newman Zone® Standard without sodium lactate (96 vs. 75 days, respectively), CAP 18 ME (85 vs. 94 days, respectively), EOS 598B42 (68 vs. 72 days, respectively), and acetate (134 vs. 125 days, respectively). These data suggest that the addition of an electron donor does not always increase the rate and extent of reductive dechlorination but will increase costs. In particular, increasing the concentration of electron donors higher than the stoichiometric demand only decreased complete microbial reductive dechlorination, which is the opposite of most standard “more time and more electrons” approaches. These data argue that site-specific electron donor demands must be evaluated, and in some cases, a monitored natural attenuation (MNA) approach is most favorable.
PubDate: 2021-10-01
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- Bio-hydrolysis of used soybean oil: environmental-friendly technology
using microbial consortium-
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Abstract: In this work, strains of Bacillus subtilis were inoculated in consortium with Rhodotorula mucilaginosa into spent soy oil as aiming to biological treatment and low-cost reuse. The microorganisms were previously isolated and selected for the lipolytic capacity of the alperujo residue generated during the processing of olive oil. For fermentation, bioassays containing Rhodotorula mucilaginosa isolated from alperujo and Candida rugosa CCMA 00371, both co-inoculated with Bacillus subtilis CCMA 0085 in medium containing (% w/v) 0.075 glucose and 0.375 (NH4)3 PO4 in 75 mL of water and 75 mL of spent soy oil. Despite the low biomass productivity, it has favorable characteristics to be used in animal feed supplementation. Spent soy oil was used as a carbon source proven by Bartha respirometer. The strains of R. mucilaginosa UFLA RAS 144 and B. subtilis CCMA 0085 are promising inoculants for oil degradation and can be applied in a waste treatment system.
PubDate: 2021-10-01
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- An evaluation into the biosorption and biodegradation of azo dyes by
indigenous siderophores-producing bacteria immobilized in chitosan-
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Abstract: The biodegradation and biosorption efficiency of an indigenous siderophores-producing bacterial community on azo dyes with immobilization in chitosan beads was evaluated in this study. 13 bacterial strains were isolated from textile wastewater streams. The bacterial strains were tested for the production of siderophores as well as their ability to decolorize toxic azo dyes in aqueous solution. Both qualitatively and quantitatively, all of the strains displayed high siderophores productivity. Furthermore, they displayed remarkable decolorization efficiency for azo dyes (Acid Black 1 and Reactive Black 5) in both free and immobilized form. The immobilization process was found not only to enhance the decolorization but also the degradation of azo dyes by the bacterial isolates. In a SEM micrograph, bacterial strains were immobilized, and the pores in chitosan bead to be trapped and adsorbed for dyes from synthetic wastewater. The extent of dye compounds degradation were examined using UV–visible and FTIR spectrophotometers on treated water samples and dye absorbed beads. After 72 h of incubation, the UV–visible analysis revealed that the bacterial community could significantly reduce both azo dyes in wastewater by 90% at 300 mgL−1 dyes initial concentration. FTIR study confirmed the bonds of these dyes were broken to form less toxic chemicals via the bacterial community immobilized in chitosan beads. The immobilized bacterial community thus demonstrated effective approach of azo dye biosorption and biodegradation.
PubDate: 2021-09-22
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- Microbial reduction of Cr(VI) in the presence of Ni, Cu and Zn by
bacterial consortium enriched from an electroplating contaminated site-
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Abstract: The bioremediation of Cr(VI) has been intensively reported in recent years, while little information about Cr(VI)-reducing consortium enriched from in-situ contaminated soil has been revealed, specifically the functional genes involved. In this study, we verified a Cr(VI) reduction process by a consortium enriched from in-situ contaminated soil through enzymatic analysis. The chromate reductase gene ChrR has been successfully amplified and further analyzed, provided solid evidence to prove the Cr(VI) bio-reduction was an enzyme-mediated process. Meanwhile, the analysis of metabolic pathways demonstrates that the consortium could detoxicate and resist Cr(VI) and co-existing metals (Ni2+, Zn2+ and Cu2+) through membrane transport and DNA repair process. The co-existing heavy metals Zn and Cu had a relatively significant negative and positive effects on Cr(VI) reduction respectively, which may play important roles in the Cr(VI) contaminated soil bioremediation.
PubDate: 2021-09-15
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- Preparation and performance evaluation of novel magnetic porous carriers
in fluidized bed bioreactor for wastewater treatment-
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Abstract: Biofilm process is a promising wastewater treatment technology and biofilm carrier (biocarrier) is regarded as the core of this process. However, the traditional commercial biocarriers have their inherent drawbacks, therefore, the development of new-type biocarrier to enhance wastewater treatment efficiency is significantly important to biofilm-based reactors. In this study, based on radical suspension polymerization, a novel kind of magnetic porous carriers (PMCs) was prepared by modifying the porous polymer carriers (PPCs) with inorganic particles, and then applied in a fluidized bed bioreactor (FBBR) with a low packing ratio of 10 % (v/v) to synthetic wastewater treatment. The results showed that this novel biocarrier possesses paramagnetism with saturation magnetization of 1.01emu/g, low density (1.26 g/cm3), excellent hydrophilicity (surface water contact angle approaching zero) and rough surface. Besides, compared with the PPCs, the developed PMCs have larger pores (up to 50 μm or more), in which the larger-sized microbes are able to colonize. Moreover, as compared to the PPCs-based FBBR, the PMCs-based reactor achieved shorter time (7 days) for biofilm formaiton and significantly enhanced NH3-N removal efficiency ( nearly 20 % increase at the level of influent NH3-N concentration about 100 mg/L). High-throughput sequencing (HTS) results indicated that this new biocarrier could promote biodiversity and improve the abundance of Nitrosomonadales (the functional bacteria for ammonia removal in the bio-system), thus enhancing the ammonification process. Therefore, the developed PMCs could be preferable biocarriers for biofilm formation and provide an alternative to the traditional suspended biocarrier, demonstrating a promising potential, even at a lower filling ratio, to enhance the pollutants removal performance.
PubDate: 2021-09-13
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- Aerobic degradation of 2,4,6-trinitrophenol by Proteus sp. strain OSES2
obtained from an explosive contaminated tropical soil-
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Abstract: A 2,4,6-trinitrophenol (TNP) degrading bacterial strain isolated from a site polluted with explosives was identified as Proteus sp. strain OSES2 via 16S rRNA gene sequencing. Metabolic investigation showed that the organism grew exponentially on 100 mg l−1 of TNP as a source of carbon, nitrogen, and energy. In addition, the growth of the organism was sustainable on 3-nitrotoluene, 2,4-dinitrotoluene, 2,4,6-trinitrotoluene, 4-nitrophenol, methyl-3-nitrobenzoate, 4-nitroaniline, aniline and nitrobenzene. Strain OSES2 was able to utilize TNP within a concentration range of 100 mg l−1 to 500 mg l−1. The specific growth rate and degradation rates on TNP were 0.01043 h−1 and 0.01766 mg l−1 h−1 respectively. Effective degradation of TNP in a chemically defined medium was evident with a gradual reduction in the concentration of TNP concomitant with an increase in cell density as well as the substantial release of ammonium (NH4+), nitrite (NO2−), and nitrate (NO3−) as metabolites in 96 h. Degradation competence of the organism was enhanced in the presence of starch and acetate. On starch-supplemented TNP, the highest specific growth rate and degradation rates were 0.02634 h−1 and 0.04458 mg l−1 h−1, respectively, while the corresponding values on acetate were 0.02341 h−1 and 0.02811 mg l−1 h−1. However, amendment with nitrogen sources yielded no substantial improvement in degradation. TNP was utilized optimally at pH 7 to 9 and within the temperature range of 30 °C to 37 °C. The enzyme hydride transferase II [HTII], encoded by the npdI gene which is the first step involved in the TNP degradation pathway, was readily expressed by the isolate thus suggesting that substrate was utilized through the classical metabolic pathway.
PubDate: 2021-09-06
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- Efficiency of sulfamethoxazole removal from wastewater using aerobic
granular sludge: influence of environmental factors-
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Abstract: The effects of adsorption, sulfamethoxazole (SMX) content, chemical oxygen demand (COD), and dissolved oxygen (DO) are recognized to be crucial for SMX removal in the aerobic granular sludge (AGS) system. Therefore, we investigated the impact of adsorption and these three different environmental factors on the SMX removal loading rate and removal efficiency of an AGS system, and determined the differences in microbial community composition under different environmental conditions. Adsorption was not the main SMX removal mechanism, as it only accounted for 5% of the total removal. The optimal SMX removal conditions were obtained for AGS when the COD, DO, and SMX concentrations were 600 mg/L, 8 mg/L, and 2,000 µg/L, respectively. The highest SMX removal efficiency was 93.53%. Variations in the three environmental factors promoted the diversity and changes of microbial communities in the AGS system. Flavobacterium, Thauera, and norank_f_Microscillaceae are key microorganisms in the AGS system. Thauera, and norank_f_Microscillaceae were sensitive to increases in SMX concentrations and beneficial for degrading high SMX concentrations. In particular, Flavobacterium abundances gradually decreased with increasing SMX concentrations.
PubDate: 2021-09-04
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- Bacterial biosurfactant increases ex situ biodiesel bioremediation in
clayey soil-
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Abstract: The contamination of soils by oily compounds has several environmental impacts, which can be reversed through bioremediation, using biosurfactants as auxiliaries in the biodegradation process. In this study, we aimed to perform ex situ bioremediation of biodiesel-contaminated soil using biosurfactants produced by Bacillus methylotrophicus. A crude biosurfactant was produced in a whey-based culture medium supplemented with nutrients and was later added to biodiesel-contaminated clayey soil. The produced lipopeptide biosurfactant could reduce the surface tension of the fermentation broth to 30.2 mN/m. An increase in the microbial population was observed in the contaminated soil; this finding can be corroborated by the finding of increased CO2 release over days of bioremediation. Compared with natural attenuation, the addition of a lower concentration of the biosurfactant (0.5% w/w in relation to the mass of diesel oil) to the soil increased biodiesel removal by about 16% after 90 days. The added biosurfactant did not affect the retention of the contaminant in the soil, which is an important factor to be considered when applying in situ bioremediation technologies.
PubDate: 2021-08-01
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- Effect on simultaneous removal of ammonia, nitrate, and phosphorus via
advanced stacked assembly biological filter for rural domestic sewage
treatment-
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Abstract: The discharge of ammonia–nitrogen (NH3–N), total nitrogen (TN), chemical oxygen demand (COD), and total phosphorus (TP) in rural sewage usually exceeds the Pollutant Discharge Standard for Urban Sewage Treatment Plants (GB18918-2002). Efficient and cost-effective removal of these pollutants cannot be simultaneously realized using conventional rural sewage treatment methods. Thus, an assembled biological filter (D50 × W50 × H113 cm), including a phosphorus removal layer filled with solid polymeric ferric sulfate and alternating aerobic-anaerobic layers, is proposed herein. The aerobic (anerobic) layers were filled with zeolite (zeolite and composite soil) at different intervals. This system was used for the treatment of synthetic sewage having COD: 122.0–227.0 mg/L; NH3–N: 29.1–47.0 mg/L; TN: 28.0–58.0 mg/L; and TP: 2.0–3.8 mg/L. Based on optimal operation conditions (40 L/h reflow rate, without artificial aeration, and 12-h operation cycle), the system showed NH3–N, TN, COD, and TP removal efficiencies of 87.1 ± 8.1, 83.4 ± 7.9, 91.0 ± 9.4, and 80.0 ± 6.4%, respectively. Further, in the pilot-scale test, under the same optimal parameters, the removal efficiencies of NH3–N, TN, COD, and TP were 78.9 ± 8.1, 75.4 ± 7.9, 82 ± 9.4, and 76 ± 6.4%, respectively. Furthermore, in the different functional units of the system, a large number of functional bacteria capable of efficiently facilitating the simultaneous removal of the different pollutants from sewage were identified. Therefore, this proposed system, which complies with current environmental discharge regulations, can be a more sustainable approach for the treatment of unattended rural sewage. Graphic abstract
PubDate: 2021-08-01
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- Bioremediation of hexavalent chromium from wastewater using bacteria-a
green technology-
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Abstract: Hexavalent chromium has high toxic effect on the ecological system. The aim of the present study is to isolate and characterize the bacteria that can reduce the toxicity of hexavalent chromium from liquid effluent. The bacterial isolate was identified as Bacillus sp. ltds1 after 16 S rRNA gene sequencing, and annotation has been submitted in National Center for Biotechnology Information (NCBI) GenBank. The bacterial strain was found able to grow in Luria Broth medium at 100 mg/L Cr6+ concentration. A maximum Cr6+ bioremediation (95.24 ± 2.08 %) could be achieved using the said isolate at 40 mg/L, pH 7, and inoculum concentration 4 % at 24 h. The residual chromium was found in the form of less toxic trivalent chromium (Cr3+), which confirms that the bacterial isolate can transform toxic Cr6+ to non-toxic Cr3+. Fourier Transform Infra-Red (FTIR) study was performed to analyze the functional groups and overall nature of chemical bonds involved in the remediation process, whereas, Energy-Dispersive Spectroscopy (EDS) studies of native and treated cells showed the changes in elemental composition in response to metal stress. Artificial Neural Network (ANN) based prediction model is developed based on experimental points. The developed model was found to predict the bioremediation of Cr6+ at various operating conditions. Particle Swarm Optimization (PSO) is used to optimize the variables like the initial concentration of metal, pH, temperature, and inoculum concentration for the said bacterial strain. The results showed that the isolate could be applied as a potential bioremediation agent for Cr6+ removal.
PubDate: 2021-08-01
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- 2,4-Dichlorophenoxyacetic acid degradation in methanogenic mixed cultures
obtained from Brazilian Amazonian soil samples-
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Abstract: 2,4-Dichlorophenoxyacetic acid (2,4-D) is the third most applied pesticide in Brazil to control broadleaf weeds in crop cultivation and pastures. Due to 2,4-D’s high mobility and long half-life under anoxic conditions, this herbicide has high probability for groundwater contamination. Bioremediation is an attractive solution for 2,4-D contaminated anoxic environments, but there is limited understanding of anaerobic 2,4-D biodegradation. In this study, methanogenic enrichment cultures were obtained from Amazonian top soil (0—40 cm) and deep soil (50 -80 cm below ground) that biotransform 2,4-D (5 µM) to 4-chlorophenol and phenol. When these cultures were transferred (10% v/v) to fresh medium containing 40 µM or 160 µM 2,4-D, the rate of 2,4-D degradation decreased, and biotransformation did not proceed beyond 4-chlorophenol and 2,4-dichlorophenol in the top and deep soil cultures, respectively. 16S rRNA gene sequencing and qPCR of a selection of microbes revealed no significant enrichment of known organohalide-respiring bacteria. Furthermore, a member of the genus Cryptanaerobacter was identified as possibly responsible for phenol conversion to benzoate in the top soil inoculated culture. Overall, these results demonstrate the effect of 2,4-D concentration on biodegradation and microbial community composition, which are both important factors when developing pesticide bioremediation technologies.
PubDate: 2021-08-01
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- Outer membrane vesicles mediated horizontal transfer of an aerobic
denitrification gene between Escherichia coli-
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Abstract: Bacterial genetic material can be horizontally transferred between microorganisms via outer membrane vesicles (OMVs) released by bacteria. Up to now, the application of vesicle-mediated horizontal transfer of “degrading genes” in environmental remediation has not been reported. In this study, the nirS gene from an aerobic denitrification bacterium, Pseudomonas stutzeri, was enclosed in a pET28a plasmid, transformed into Escherichia coli (E. coli) DH5α and expressed in E. coli BL21. The E. coli DH5α released OMVs containing the recombination plasmid pET28a–nirS-EGFP. When compared with the free pET28a–nirS-EGFP plasmid’s inability to transform, nirS in OMVs could be transferred into E. coli BL21 with the transformation frequency of 2.76 × 106 CFU/g when the dosage of OMVs was 200 µg under natural conditions, and nirS could express successfully in recipient bacteria. Furthermore, the recipient bacteria that received OMVs containing pET28a–nirS-EGFP could produce 18.16 U/mL activity of nitrite reductase.
PubDate: 2021-08-01
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- Anaerobic semi-fixed bed biofilm reactor (An-SFB-BR) for treatment of high
concentration p-nitrophenol wastewater under shock loading conditions-
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Abstract: P-nitrophenol (PNP or 4-NP) has been widely used as a biorefractory raw material in chemical industry, whereas been highly concerned for its characteristics of mutagenic/carcinogenic activity and food chain bioaccumulation. In this study, an anaerobic semi-fixed bed biofilm reactor (An-SFB-BR) was constructed and used to treat PNP wastewater which discharged from chemical industries. Experimental results revealed that the An-SFB-BR was successfully cultivated with the gradually increasing of influent PNP from 0 to 540 mg/L (gradually increased 10 mg/L every time in stage II and 30–50 mg/L for stage III), with the observation of an average removal efficiency of 98% for PNP and 80% for chemical oxygen demand (COD), also a biogas production and biogas production rate of 2.1 L/(L·d) and 0.57 m3/kg-COD, respectively. Finally, the conversion rate of P-aminophenol (PAP), the primary intermediate of PNP reached 80% after An-SFB-BR biodegradation. A relatively stable pH was maintained throughout the entire process, and insignificant VFA accumulation. The reactor exhibited a strong toxic shock resistance, and 16S rRNA sequencing results demonstrated that the dominant microbial community changed slightly with the gradually increasing of PNP concentration, which guaranteed the PNP removal efficiency.
PubDate: 2021-08-01
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