Showing papers in "Biodegradation in 2018"

Aerobic bacteria degrading both n -alkanes and aromatic hydrocarbons: an undervalued strategy for metabolic diversity and flexibility

Abstract: Environmental pollution with petroleum toxic products has afflicted various ecosystems, causing devastating damage to natural habitats with serious economic implications. Some crude oil components may serve as growth substrates for microorganisms. A number of bacterial strains reveal metabolic capacities to biotransform various organic compounds. Some of the hydrocarbon degraders are highly biochemically specialized, while the others display a versatile metabolism and can utilize both saturated aliphatic and aromatic hydrocarbons. The extended catabolic profiles of the latter group have been subjected to systematic and complex studies relatively rarely thus far. Growing evidence shows that numerous bacteria produce broad biochemical activities towards different hydrocarbon types and such an enhanced metabolic potential can be found in many more species than the already well-known oil-degraders. These strains may play an important role in the removal of heterogeneous contamination. They are thus considered to be a promising solution in bioremediation applications. The main purpose of this article is to provide an overview of the current knowledge on aerobic bacteria involved in the mineralization or transformation of both n-alkanes and aromatic hydrocarbons. Variant scientific approaches enabling to evaluate these features on biochemical as well as genetic levels are presented. The distribution of multidegradative capabilities between bacterial taxa is systematically shown and the possibility of simultaneous transformation of complex hydrocarbon mixtures is discussed. Bioinformatic analysis of the currently available genetic data is employed to enable generation of phylogenetic relationships between environmental strain isolates belonging to the phyla Actinobacteria, Proteobacteria, and Firmicutes. The study proves that the co-occurrence of genes responsible for concomitant metabolic bioconversion reactions of structurally-diverse hydrocarbons is not unique among various systematic groups.

Anaerobic ammonium oxidation linked to sulfate and ferric iron reduction fuels nitrogen loss in marine sediments.

Abstract: Availability of fixed nitrogen is a pivotal driver on primary productivity in the oceans, thus the identification of key processes triggering nitrogen losses from these ecosystems is of major importance as they affect ecosystems function and consequently global biogeochemical cycles. Denitrification and anaerobic ammonium oxidation coupled to nitrite reduction (Anammox) are the only identified marine sinks for fixed nitrogen. The present study provides evidence indicating that anaerobic ammonium oxidation coupled to the reduction of sulfate, the most abundant electron acceptor present in the oceans, prevails in marine sediments. Tracer analysis with 15N-ammonium revealed that this microbial process, here introduced as Sulfammox, accounts for up to 5 μg 15N2 produced g−1 day−1 in sediments collected from the eastern tropical North Pacific coast. Raman and X-ray diffraction spectroscopies revealed that elemental sulfur and sphalerite (ZnFeS) were produced, besides free sulfide, during the course of Sulfammox. Anaerobic ammonium oxidation linked to Fe(III) reduction (Feammox) was also observed in the same marine sediments accounting for up to 2 μg 15N2 produced g−1 day−1. Taxonomic characterization, based on 16S rRNA gene sequencing, of marine sediments performing the Sulfammox and Feammox processes revealed the microbial members potentially involved. These novel nitrogen sinks may significantly fuel nitrogen loss in marine environments. These findings suggest that the interconnections among the oceanic biogeochemical cycles of N, S and Fe are much more complex than previously considered.

1,4-Dioxane degradation characteristics of Rhodococcus aetherivorans JCM 14343.

Abstract: Rhodococcus aetherivorans JCM 14343 can degrade 1,4-dioxane as a sole carbon and energy source. This study aimed to characterize this 1,4-dioxane degradation ability further, and assess the potential use of the strain for 1,4-dioxane removal in industrial wastewater. Strain JCM 14343 was able to degrade 1,4-dioxane inducibly, and its 1,4-dioxane degradation was also induced by tetrahydrofuran and 1,4-butanediol. The demonstration that 1,4-butanediol not only induced but also enhanced 1,4-dioxane degradation was a novel finding of this study. Although strain JCM 14343 appeared not to be an effective 1,4-dioxane degrader considering the maximum specific 1,4-dioxane degradation rate (0.0073 mg-dioxane/mg-protein/h), half saturation concentration (59.2 mg/L), and cell yield (0.031 mg-protein/mg-1,4-dioxane), the strain could degrade over 1100 mg/L of 1,4-dioxane and maintain its degradation activity at a wide range of temperature (5-40 °C) and pH (4-9) conditions. This suggests the usefulness of strain JCM 14343 in 1,4-dioxane treatment under acidic and cold conditions. In addition, 1,4-dioxane degradation experiments in the presence of ethylene glycol (EG) or other cyclic ethers revealed that 1,4-dioxane degradation by strain JCM 14343 was inhibited in the presence of other cyclic ethers, but not by EG, suggesting certain applicability of strain JCM 14343 for industrial wastewater treatment.

Biodegradation of sulfonamides by Shewanella oneidensis MR-1 and Shewanella sp. strain MR-4.

Abstract: Because of extensive sulfonamides application in aquaculture and animal husbandry and the consequent increase in sulfonamides discharged into the environment, strategies to remediate sulfonamide-contaminated environments are essential. In this study, the resistance of Shewanella oneidensis MR-1 and Shewanella sp. strain MR-4 to the sulfonamides sulfapyridine (SPY) and sulfamethoxazole (SMX) were determined, and sulfonamides degradation by these strains was assessed. Shewanella oneidensis MR-1 and Shewanella sp. strain MR-4 were resistant to SPY and SMX concentrations as high as 60 mg/L. After incubation for 5 days, 23.91 ± 1.80 and 23.43 ± 2.98% of SPY and 59.88 ± 1.23 and 63.89 ± 3.09% of SMX contained in the medium were degraded by S. oneidensis MR-1 and Shewanella sp. strain MR-4, respectively. The effects of the initial concentration of the sulfonamides and initial pH of the medium on biodegradation, and the degradation of different sulfonamides were assessed. The products were measured by LC-MS; with SPY as a substrate, 2-AP (2-aminopyridine) was the main stable metabolite, and with SMX as a substrate, 3A5MI (3-amino-5-methyl-isoxazole) was the main stable metabolite. The co-occurrence of 2-AP or 3A5MI and 4-aminobenzenesulfonic acid suggests that the initial step in the biodegradation of the two sulfonamides is S-N bond cleavage. These results suggest that S. oneidensis MR-1 and Shewanella sp. strain MR-4 are potential bacterial resources for biodegrading sulfonamides and therefore bioremediation of sulfonamide-polluted environments.

Simultaneous nitrification–denitrification and microbial community profile in an oxygen-limiting intermittent aeration SBBR with biodegradable carriers

Abstract: To enhance the startup and efficient simultaneous nitrification and denitrification for sewage treatment, sequencing batch biofilm reactors (SBBRs) partially coupled with rice husk were established and operated under various intermittent micro-aeration cycles (IMCs) and COD/N ratios under oxygen-limiting intermittent aeration conditions. Experimental results showed that the increase of IMCs with non-aeration/micro-aeration mode of (8 h/4 h)1 to (2 h/1 h)4 in a 12 h-cycle accelerated the startup performance and improved NH4+–N and COD removal. NH4+–N, TN and COD removal efficiencies were 98.7 ± 0.9, 89.2 ± 5.2 and 82.9 ± 6.7% at COD/N ratio of 7.6 with the highest IMCs in SBBR, respectively. Higher TN removal efficiencies of 87.2 ± 4.0 and 58.1 ± 3.5% were also achieved at lower COD/N ratio of 5.6 and 2.8, respectively. In SBBRs with various IMCs, facultative denitrifier like genus Acinetobacter and solid-phase denitrifier belonging to Comamonadaceae family were enriched. However, aerobic denitrifiers with function of heterotrophic nitrification like Paracoccus were favored to enrich under higher IMCs condition, and more anoxic denitrifiers like sulfur-based autotrophic denitrifier Thiothrix and heterotrophic denitrifiers like Pseudomonas and Methyloversatilis were observed at lower IMCs condition. Autotrophic nitrifier (Nitrosomonas and Nitrosipra) and heterotrophic nitrifiers both contributed to the efficient nitrification.

Anaerobic degradation of 1-methylnaphthalene by a member of the Thermoanaerobacteraceae contained in an iron-reducing enrichment culture.

Abstract: An anaerobic culture (1MN) was enriched with 1-methylnaphthalene as sole source of carbon and electrons and Fe(OH)3 as electron acceptor. 1-Naphthoic acid was produced as a metabolite during growth with 1-methylnaphthalene while 2-naphthoic acid was detected with naphthalene and 2-methylnaphthalene. This indicates that the degradation pathway of 1-methylnaphthalene might differ from naphthalene and 2-methylnaphthalene degradation in sulfate reducers. Terminal restriction fragment length polymorphism and pyrosequencing revealed that the culture is mainly composed of two bacteria related to uncultured Gram-positive Thermoanaerobacteraceae and uncultured gram-negative Desulfobulbaceae. Stable isotope probing showed that a 13C-carbon label from 13C10-naphthalene as growth substrate was mostly incorporated by the Thermoanaerobacteraceae. The presence of putative genes involved in naphthalene degradation in the genome of this organism was confirmed via assembly-based metagenomics and supports that it is the naphthalene-degrading bacterium in the culture. Thermoanaerobacteraceae have previously been detected in oil sludge under thermophilic conditions, but have not been shown to degrade hydrocarbons so far. The second member of the community belongs to the Desulfobulbaceae and has high sequence similarity to uncultured bacteria from contaminated sites including recently proposed groundwater cable bacteria. We suggest that the gram-positive Thermoanaerobacteraceae degrade polycyclic aromatic hydrocarbons while the Desulfobacterales are mainly responsible for Fe(III) reduction.

Biodegradation and chemotaxis of polychlorinated biphenyls, biphenyls, and their metabolites by Rhodococcus spp.

Abstract: Two biphenyl-degrading bacterial strains, SS1 and SS2, were isolated from polychlorinated biphenyl (PCB)-contaminated soil. They were identified as Rhodococcus ruber and Rhodococcus pyridinivorans based on the 16S rRNA gene sequence, as well as morphological, physiological and biochemical characteristics. SS1 and SS2 exhibited tolerance to 2000 and 3000 mg/L of biphenyl. And they could degrade 83.2 and 71.5% of 1300 mg/L biphenyl within 84 h, respectively. In the case of low-chlorinated PCB congeners, benzoate and 3-chlorobenzoate, the degradation activities of SS1 and SS2 were also significant. In addition, these two strains exhibited chemotactic response toward TCA-cycle intermediates, benzoate, biphenyl and 2-chlorobenzoate. This study indicated that, like the flagellated bacteria, non-flagellated Rhodococcus spp. might actively seek substrates through the process of chemotaxis once the substrates are depleted in their surroundings. Together, these data provide supporting evidence that SS1 and SS2 might be good candidates for restoring biphenyl/PCB-polluted environments.

Biodegradation of n-alkanes on oil-seawater interfaces at different temperatures and microbial communities associated with the degradation.

Abstract: Oil biodegradation studies have mainly focused on microbial processes in dispersions, not specifically on the interfaces between the oil and the seawater in the dispersions In this study, a hydrophobic adsorbent system, consisting of Fluortex fabrics, was used to investigate biodegradation of n-alkanes and microbial communities on oil–seawater interfaces in natural non-amended seawater The study was performed over a temperature range from 0 to 20 °C, to determine how temperature affected biodegradation at the oil–seawater interfaces Biodegradation of n-alkanes were influenced both by seawater temperature and chain-length Biotransformation rates of n-alkanes decreased by reduced seawater temperature Low rate coefficients at a seawater temperature of 0 °C were probably associated with changes in physical–chemical properties of alkanes The primary bacterial colonization of the interfaces was predominated by the family Oceanospirillaceae at all temperatures, demonstrating the wide temperature range of these hydrocarbonoclastic bacteria The mesophilic genus Oleibacter was predominant at the seawater temperature of 20 °C, and the psychrophilic genus Oleispira at 5 and 0 °C Upon completion of n-alkane biotransformation, other oil-degrading and heterotrophic bacteria became abundant, including Piscirickettsiaceae (Cycloclasticus), Colwelliaceae (Colwellia), Altermonadaceae (Altermonas), and Rhodobacteraceae This is one of a few studies that describe the biodegradation of oil, and the microbial communities associated with the degradation, directly at the oil–seawater interfaces over a large temperature interval

Screening of a beta-cypermethrin-degrading bacterial strain Brevibacillus parabrevis BCP-09 and its biochemical degradation pathway

Abstract: A novel beta-cypermethrin (Beta-CP)-degrading strain isolated from activated sludge was identified as Brevibacillus parabrevis BCP-09 based on its morphological and physio-biochemical characteristics, and 16S rRNA gene analysis. Strain BCP-09 could effectively degrade Beta-CP at pH 5.0–9.0, 20–40 °C, and 10–500 mg L−1 Beta-CP. Under optimal conditions (pH 7.41, 38.9 °C, 30.9 mg L−1 Beta-CP), 75.87% Beta-CP was degraded within 3 days. Beta-CP degradation (half-life, 33.45 h) and strain BCP-09 growth were respectively described using first-order-kinetic and logistic-kinetic models. Seven metabolites were detected by high-performance liquid chromatography and gas chromatography-mass spectrometry- methyl salicylate, catechol, phthalic acid, salicylic acid, 3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropanecarboxylic acid, 3-phenoxybenzaldehyde, and 3-phenoxybenzoic acid (3-PBA). The major Beta-CP metabolite, 3-PBA was further degraded into phenol, benzoic acid, and 4-methylhexanoic acid. BCP-09 also degraded aromatic compounds such as phenol, catechol, and protocatechuic acid. Beta-CP appears to be mainly degraded into 3-PBA, which is continuously degraded into smaller benzene or chain compounds. Thus, strain BCP-09 could form a complete degradation system for Beta-CP and might be considered a promising strain for application in the bioremediation of environments and agricultural products polluted by Beta-CP.

Nitrogen removal performance and microbial community of an enhanced multistage A/O biofilm reactor treating low-strength domestic wastewater.

Abstract: The low-strength domestic wastewater (LSDW) treatment with low chemical oxygen demand (COD) has drawn extensive attention for the poor total nitrogen (TN) removal performance. In the present study, an enhanced multistage anoxic/oxic (A/O) biofilm reactor was designed to improve the TN removal performance of the LSDW treatment. Efficient nitrifying and denitrifying biofilm carriers were cultivated and then filled into the enhanced biofilm reactor as the sole microbial source. Step-feed strategy and internal recycle were adopted to optimize the substrate distribution and the organics utilization. Key operational parameters were optimized to obtain the best nitrogen and organics removal efficiencies. A hydraulic retention time of 8 h, an influent distribution ratio of 2:1 and an internal recycle ratio of 200% were tested as the optimum parameters. The ammonium, TN and COD removal efficiencies under the optimal operational parameters separately achieved 99.75 ± 0.21, 59.51 ± 1.95 and 85.06 ± 0.79% with an organic loading rate at around 0.36 kg COD/m3 d. The high-throughput sequencing technology confirmed that nitrifying and denitrifying biofilm could maintain functional bacteria in the system during long-period operation. Proteobacteria and Bacteroidetes were the dominant phyla in all the nitrifying and denitrifying biofilm samples. Nitrosomonadaceae_uncultured and Nitrospira sp. stably existed in nitrifying biofilm as the main nitrifiers, while several heterotrophic genera, such as Thauera sp. and Flavobacterium sp., acted as potential genera responsible for TN removal in denitrifying biofilm. These findings suggested that the enhanced biofilm reactor could be a promising route for the treatment of LSDW with a low COD level.

H2S biotreatment with sulfide-oxidizing heterotrophic bacteria

Abstract: Many industrial activities produce H2S, which is toxic at high levels and odorous at even very low levels. Chemolithotrophic sulfur-oxidizing bacteria are often used in its remediation. Recently, we have reported that many heterotrophic bacteria can use sulfide:quinone oxidoreductase and persulfide dioxygenase to oxidize H2S to thiosulfate and sulfite. These bacteria may also potentially be used in H2S biotreatment. Here we report how various heterotrophic bacteria with these enzymes were cultured with organic compounds and the cells were able to rapidly oxidize H2S to zero-valence sulfur and thiosulfate, causing no apparent acidification. Some also converted the produced thiosulfate to tetrathionate. The rates of sulfide oxidation by some of the tested bacteria in suspension, ranging from 8 to 50 µmol min−1 g−1 of cell dry weight at pH 7.4, sufficient for H2S biotreatment. The immobilized bacteria removed H2S as efficiently as the bacteria in suspension, and the inclusion of Fe3O4 nanoparticles during immobilization resulted in increased efficiency for sulfide removal, in part due to chemical oxidation H2S by Fe3O4. Thus, heterotrophic bacteria may be used for H2S biotreatment under aerobic conditions.

Ammonium removal using algae-bacteria consortia: the effect of ammonium concentration, algae biomass, and light.

Abstract: In this study, the effects of ammonium nitrogen concentration, algae biomass concentration, and light conditions (wavelength and intensity) on the ammonium removal efficiency of algae-bacteria consortia from wastewater were investigated. The results indicated that ammonium concentration and light intensity had a significant impact on nitrification. It was found that the highest ammonia concentration (430 mg N/L) in the influent resulted in the highest ammonia removal rate of 108 ± 3.6 mg N/L/days, which was two times higher than the influent with low ammonia concentration (40 mg N/L). At the lowest light intensity of 1000 Lux, algae biomass concentration, light wavelength, and light cycle did not show a significant effect on the performance of algal–bacterial consortium. Furthermore, the ammonia removal rate was approximately 83 ± 1.0 mg N/L/days, which was up to 40% faster than at the light intensity of 2500 Lux. It was concluded that the algae-bacteria consortia can effectively remove nitrogen from wastewater and the removal performance can be stabilized and enhanced using the low light intensity of 1000 Lux that is also a cost-effective strategy.

Effects of fungal-assisted algal harvesting through biopellet formation on pesticides in water.

Abstract: Recent research has demonstrated the potential of using filamentous fungi to form pellets with microalgae (biopellets), in order to facilitate harvesting of microalgae from water following algae-based treatment of wastewater In parallel, there is a need to develop techniques for removing organic pollutants such as pesticides and pharmaceuticals from wastewater In experiments using the microalga Chlorella vulgaris, the filamentous fungus Aspergillus niger and biopellets composed of these microorganisms, this study investigated whether fungal-assisted algal harvesting can also remove pesticides from contaminated water A mixture of 38 pesticides was tested and the concentrations of 17 of these were found to be reduced significantly in the biopellet treatment, compared with the control After harvesting, the concentration of total pesticides in the algal treatment did not differ significantly from that in the control However, in the fungal treatment and biopellet treatment, the concentration was significantly lower (596 ± 20 µg/L and 561 ± 28 µg/L, respectively) than in the control (666 ± 10 µg/L) Thus fungal-assisted algal harvesting through biopellet formation can also provide scope for removing organic pollutants from wastewater, with removal mainly being performed by the fungus

Modulation of microbial consortia enriched from different polluted environments during petroleum biodegradation.

Abstract: Environmental microbial communities are key players in the bioremediation of hydrocarbon pollutants. Here we assessed changes in bacterial abundance and diversity during the degradation of Tunisian Zarzatine oil by four indigenous bacterial consortia enriched from a petroleum station soil, a refinery reservoir soil, a harbor sediment and seawater. The four consortia were found to efficiently degrade up to 92.0% of total petroleum hydrocarbons after 2 months of incubation. Illumina 16S rRNA gene sequencing revealed that the consortia enriched from soil and sediments were dominated by species belonging to Pseudomonas and Acinetobacter genera, while in the seawater-derived consortia Dietzia, Fusobacterium and Mycoplana emerged as dominant genera. We identified a number of species whose relative abundances bloomed from small to high percentages: Dietzia daqingensis in the seawater microcosms, and three OTUs classified as Acinetobacter venetianus in all two soils and sediment derived microcosms. Functional analyses on degrading genes were conducted by comparing PCR results of the degrading genes alkB, ndoB, cat23, xylA and nidA1 with inferences obtained by PICRUSt analysis of 16S amplicon data: the two data sets were partly in agreement and suggest a relationship between the catabolic genes detected and the rate of biodegradation obtained. The work provides detailed insights about the modulation of bacterial communities involved in petroleum biodegradation and can provide useful information for in situ bioremediation of oil-related pollution.

Anaerobic degradation of 2,4-dichlorophenoxyacetic acid by Thauera sp. DKT

Abstract: Thauera sp. strain DKT isolated from sediment utilized 2,4-dichlorophenoxyacetic acid (2,4D) and its relative compounds as sole carbon and energy sources under anaerobic conditions and used nitrate as an electron acceptor. The determination of 2,4D utilization at different concentrations showed that the utilization curve fitted well with the Edward model with the maximum degradation rate as 0.017 ± 0.002 mM/day. The supplementation of cosubstrates (glucose, acetate, sucrose, humate and succinate) increased the degradation rates of all tested chemical substrates in both liquid and sediment slurry media. Thauera sp. strain DKT transformed 2,4D to 2,4-dichlorophenol (2,4DCP) through reductive side-chain removal then dechlorinated 2,4DCP to 2-chlorophenol (2CP), 4-chlorophenol (4CP) and phenol before complete degradation. The relative degradation rates by the isolate in liquid media were: phenol > 2,4DCP > 2CP > 4CP > 2,4D ≈ 3CP. DKT augmentation in sediment slurry enhanced the degradation rates of 2,4D and chlorophenols. The anaerobic degradation rates in the slurry were significantly slower compared to the rates in liquid media.

Exploring potential applications of a novel extracellular polymeric substance synthesizing bacterium (Bacillus licheniformis) isolated from gut contents of earthworm (Metaphire posthuma) in environmental remediation.

Abstract: The aim was to isolate, characterize, and explore potentials of gut bacteria from the earthworm (Metaphire posthuma) and imply these bacteria for remediation of Cu(II) and Zn(II). An extracellular polymeric substance (EPS) producing gut bacteria (Bacillus licheniformis strain KX657843) was isolated and identified based on 16S rRNA sequencing and phylogenetic analysis. The strain showed maximum tolerance of 8 and 6 mM for Cu(II) and Zn(II) respectively. It removed 34.5% of Cu(II) and 54.4% of Zn(II) at 25 mg L-1 after 72 and 96 h incubation respectively. The bacteria possessed a great potential to produce indole acetic acid (38.49 μg mL-1) at 5 mg mL-1 L-tryptophan following 12 days incubation. The sterilized seeds of mung beans (Vigna radiata) displayed greater germination and growth under bacterium enriched condition. We observed that the bacterial strain phosphate solubilization ability with a maximum of 204.2 mg L-1 in absence of Cu(II) and Zn(II). Endowed with biosurfactant property the bacterium exhibited 24% emulsification index. The bacterium offered significant potential of plant growth promotion, Cu(II) and Zn(II) removal, and as such this study is the first report on EPS producing B. licheniformis KX657843 from earthworm which can be applied as powerful tool in remediation programs of Cu(II) and Zn(II) contaminated sites.

Simultaneous nitrification and denitrification with different mixed nitrogen loads by a hypothermia aerobic bacterium.

Abstract: Microorganism with simultaneous nitrification and denitrification ability plays a significant role in nitrogen removal process, especially in the eutrophic waters with excessive nitrogen loads. The nitrogen removal capacity of microorganism may suffer from low temperature or nitrite nitrogen source. In this study, a hypothermia aerobic nitrite-denitrifying bacterium, Pseudomonas tolaasii strain Y-11, was selected to determine the simultaneous nitrification and denitrification ability with mixed nitrogen source at 15 °C. The sole nitrogen removal efficiencies of strain Y-11 in simulated wastewater were obtained. After 24 h of incubation at 15 °C, the ammonium nitrogen fell below the detection limit from an initial value of 10.99 mg/L. Approximately 88.0 ± 0.33% of nitrate nitrogen was removed with the initial concentration of 11.78 mg/L and the nitrite nitrogen was not detected with the initial concentration of 10.75 mg/L after 48 h of incubation at 15 °C. Additionally, the simultaneous nitrification and denitrification nitrogen removal ability of P. tolaasii strain Y-11 was evaluated using low concentration of mixed NH4+-N and NO3−–N/NO2−–N (about 5 mg/L-N each) and high concentration of mixed NH4+–N and NO3−–N/NO2−–N (about 100 mg/L-N each). There was no nitrite nitrogen accumulation at the time of evaluation. The results demonstrated that P. tolaasii strain Y-11 had higher simultaneous nitrification and denitrification capacity with low concentration of mixed inorganic nitrogen sources and may be applied in low temperature wastewater treatment.

Anaerobic biotransformation of hexachlorocyclohexane isomers by Dehalococcoides species and an enrichment culture

Abstract: The biotransformation of hexachlorocyclohexane isomers (HCH) by two Dehalococcoides mccartyi strains (195 and BTF08) and an enrichment culture was investigated and compared to conversion by the obligate anaerobic strain Clostridium pasteurianum strain DSMZ 525. The D. mccartyi strains preferentially transformed γ-HCH over α-HCH and δ-HCH isomers while β-HCH biotransformation was not significant. In case of the enrichment culture, γ-HCH was preferentially transformed over the δ-HCH, β-HCH and α-HCH isomers. Major observed metabolites in both cases were tetrachlorocyclohexene and as end products monochlorobenzene (MCB) and benzene. Dechlorination of the γ-HCH isomer was linked to an increase in cell numbers for strain 195. γ-HCH transformation was linked to considerable carbon stable isotope fractionation with the enrichment factor ec = − 5.5 ± 0.8‰ for D. mccartyi strain 195, ec = − 3.1 ± 0.4‰ for the enrichment culture and ec = − 4.1 ± 0.6‰ for co-metabolic transformation by C. pasteurianum.

Characteristics and metabolic pathway of acetamiprid biodegradation by Fusarium sp. strain CS-3 isolated from soil.

Abstract: An acetamiprid-degrading fungus was isolated from contaminated soil and identified as Fusarium sp. strain CS-3 based on physiological, biochemical, and molecular analyses. Strain CS-3 exploited 50 mg/L as the sole carbon source in liquid culture, removing 98% in 96 h. Strain CS-3 retained its acetamiprid degradation abilities over a wide range of pH (5.0–8.0) and temperature (20–42 °C). HPLC–MS analysis showed that N′-[(6-chloropyridin-3-yl)methyl]-N-methylacetamide, 2-chloro-5-hydroxymethylpyridine, and 6-chloronicotinic acid were identified as the most predominant metabolites, forming the basis for a newly described acetamiprid degradation pathway. Strain CS-3 efficiently degraded 99.6% of 50 mg/kg acetamiprid in soil, indicating potential for soil remediation.

Biochemical pathways and enhanced degradation of di- n -octyl phthalate (DOP) in sequencing batch reactor (SBR) by Arthrobacter sp. SLG-4 and Rhodococcus sp. SLG-6 isolated from activated sludge

Abstract: Two bacterial strains designated as Arthrobacter sp. SLG-4 and Rhodococcus sp. SLG-6, capable of utilizing di-n-octyl phthalate (DOP) as sole source of carbon and energy, were isolated from activated sludge. The analysis of DOP degradation intermediates indicated Arthrobacter sp. SLG-4 could completely degrade DOP. Whereas DOP could not be mineralized by Rhodococcus sp. SLG-6 and the final metabolic product was phthalic acid (PA). The proposed DOP degradation pathway by Arthrobacter sp. SLG-4 was that strain SLG-4 initially transformed DOP to PA via de-esterification pathway, and then PA was metabolized to protocatechuate acid and eventually converted to tricarboxylic acid (TCA) cycle through meta-cleavage pathway. Accordingly, Phthalate 3,4-dioxygenase genes (phtA) responsible for PA degradation were successfully detected in Arthrobacter sp. SLG-4 by real-time quantitative PCR (q-PCR). q-PCR analysis demonstrated that the quantity of phthalate 3,4-dioxygenase was positively correlated to DOP degradation in SBRs. Bioaugmentation by inoculating DOP-degrading bacteria effectively shortened the start-up of SBRs and significantly enhanced DOP degradation in bioreactors. More than 91% of DOP (500 mg L−1) was removed in SBR bioaugmented with bacterial consortium, which was double of the control SBR. This study suggests bioaugmentation is an effective and feasible technique for DOP bioremediation in practical engineering.

Kinetics study of nicosulfuron degradation by a Pseudomonas nitroreducens strain NSA02

Abstract: A bacterial strain NSA02, isolated from contaminated soil and identified as Pseudomonas nitroreducens based on partial 16S rDNA gene sequence analysis and BIOLOG microbiology analysis, was used to study biodegradation of nicosulfuron in the culture medium. The optimal degradation conditions were determined to be 30 °C and pH 7.0. Batch tests were performed for seven different initial substrate concentrations to observe substrate degradation and associated cell growth. The biodegradation kinetics was found to follow a first-order model with regression values greater than 0.98. Specific degradation rate and specific growth rate of bacterial cells were observed to follow substrate inhibition kinetics, and the maximum values of both rates were observed at 100 mg L−1 of nicosulfuron concentration. Kinetic parameters of three substrate inhibition models (Haldane, Aiba–Edwards and Teissier–Edwards) were fitted to the relationship between those rates and substrate concentrations. With the date obtained, Haldane and Teissier–Edwards models provide better representation when compared to Aiba–Edwards model. Inoculating nicosulfuron-treated soil samples with strain NSA02 resulted in a 5–6 times higher rate of nicosulfuron removal than that in non-inoculated soil. Five metabolites of nicosulfuron degradation were detected and identified by liquid chromatography mass spectrometry, and three possible biotransformation pathways were proposed. These results highlight the potential of the isolated bacterium to be used in the bioremediation of nicosulfuron-contaminated soils.

A new aerobic chemolithoautotrophic arsenic oxidizing microorganism isolated from a high Andean watershed.

Abstract: Biological arsenic oxidation has been suggested as a key biogeochemical process that controls the mobilization and fate of this metalloid in aqueous environments. To the best of our knowledge, only four aerobic chemolithoautotrophic arsenite-oxidizing (CAO) bacteria have been shown to grow via direct arsenic oxidation and to have the essential genes for chemolithoautotrophic arsenite oxidation. In this study, a new CAO bacterium was isolated from a high Andean watershed evidencing natural dissolved arsenic attenuation. The bacterial isolate, designated TS-1, is closely related to the Ancylobacter genus, in the Alphaproteobacteria class. Results showed that TS-1 has genes for arsenite oxidation and carbon fixation. The dependence of bacterial growth from arsenite oxidation was demonstrated. In addition, a mathematical model was suggested and the kinetic parameters were obtained by simultaneously fitting the biomass growth, arsenite depletion curves, and arsenate production. This research increases the knowledge of chemolithoautotrophic arsenic oxidizing microorganisms and its potential role as a driver for natural arsenic attenuation.

Contaminant concentration versus flow velocity: drivers of biodegradation and microbial growth in groundwater model systems.

Abstract: Aromatic hydrocarbons belong to the most abundant contaminants in groundwater systems. They can serve as carbon and energy source for a multitude of indigenous microorganisms. Predictions of contaminant biodegradation and microbial growth in contaminated aquifers are often vague because the parameters of microbial activity in the mathematical models used for predictions are typically derived from batch experiments, which don't represent conditions in the field. In order to improve our understanding of key drivers of natural attenuation and the accuracy of predictive models, we conducted comparative experiments in batch and sediment flow-through systems with varying concentrations of contaminant in the inflow and flow velocities applying the aerobic Pseudomonas putida strain F1 and the denitrifying Aromatoleum aromaticum strain EbN1. We followed toluene degradation and bacterial growth by measuring toluene and oxygen concentrations and by direct cell counts. In the sediment columns, the total amount of toluene degraded by P. putida F1 increased with increasing source concentration and flow velocity, while toluene removal efficiency gradually decreased. Results point at mass transfer limitation being an important process controlling toluene biodegradation that cannot be assessed with batch experiments. We also observed a decrease in the maximum specific growth rate with increasing source concentration and flow velocity. At low toluene concentrations, the efficiencies in carbon assimilation within the flow-through systems exceeded those in the batch systems. In all column experiments the number of attached cells plateaued after an initial growth phase indicating a specific "carrying capacity" depending on contaminant concentration and flow velocity. Moreover, in all cases, cells attached to the sediment dominated over those in suspension, and toluene degradation was performed practically by attached cells only. The observed effects of varying contaminant inflow concentration and flow velocity on biodegradation could be captured by a reactive-transport model. By monitoring both attached and suspended cells we could quantify the release of new-grown cells from the sediments to the mobile aqueous phase. Studying flow velocity and contaminant concentrations as key drivers of contaminant transformation in sediment flow-through microcosms improves our system understanding and eventually the prediction of microbial biodegradation at contaminated sites.

The effect of methanogenesis inhibition, inoculum and substrate concentration on hydrogen and carboxylic acids production from cassava wastewater

Abstract: Manipueira is a carbohydrate-rich agro-industrial waste from cassava processing. It is considered well suitable for biotechnological processes, such as hydrogen and carboxylic acids production, due to the high content of easily degradable organic matter. However, the proper methanogenesis inhibition method, inoculum type, and organic loads are factors still limiting the processes. The objective in this work was to evaluate the effects of such factors on byproducts production in anaerobic reactors. Batch experiments were conducted with 2.3-L flasks during two operational phases. In the first phase (P1), inhibition of methanogens in the sludge was evaluated using acetylene (1% v/v of headspace) and heat treatment (120 °C, 1 atm for 30 min). In the second phase (P2), three inoculum types obtained from common anaerobic sludges (bovine rumen and sludges from municipal and textile industrial wastewater treatment plants) were individually assayed. P2 aimed to identify the best inoculum, based on hydrogen production ability, which was tested for three initial concentrations of manipueira in terms of chemical oxygen demand (COD) (10, 20 and 40 g O2/L). Results of P1 indicated that either acetylene or heat treatment efficiently inhibited methanogenesis, with no methane production. However, the maximum H2 production potential by applying heat treatment (~ 563 mL) was more than twice compared with that by acetylene treatment (~ 257 mL); and butyrate was the main carboxylic acid by-product (~ 3 g/L). In P2 experiments after sludge heat treatment, the highest hydrogen yield (1.66 ± 0.07 mol H2/mol glucose) and caproic acid production (~ 2 g/L) were observed at 20 g O2/L of manipueira COD, when bovine rumen was the inoculum. The primary metabolic degradation products in all P2 experiments were ethanol, acetic, butyric, propionic and caproic acids. The finding of caproic acid detection indicated that the applied conditions in manipueira anaerobic degradation favored carbon chain elongation over methanogenesis.

Biodegradation of pentafluorosulfanyl-substituted aminophenol in Pseudomonas spp.

Abstract: The pentafluorosulfanyl (SF5-) substituent conveys properties that are beneficial to drugs and agrochemicals. As synthetic methodologies improve the number of compounds containing this group will expand and these chemicals may be viewed as emerging pollutants. As many microorganisms can degrade aromatic xenobiotics, we investigated the catabolism of SF5-substituted aminophenols by bacteria and found that some Pseudomonas spp. can utilise these compounds as sole carbon and energy sources. GC-MS analysis of the culture supernatants from cultures grown in 5-(pentafluorosulfanyl) 2-aminophenol demonstrated the presence of the N-acetylated derivative of the starting substrate and 4-(pentafluorosulfanyl)catechol. Biotransformation experiments with re-suspended cells were also conducted and fluorine-19 NMR analyses of the organic extract and aqueous fraction from suspended cell experiments revealed new resonances of SF5-substituted intermediates. Supplementation of suspended cell cultures with yeast extract dramatically improved the degradation of the substrate as well as the release of fluoride ion. 4-(Pentafluorosulfanyl)catechol was shown to be a shunt metabolite and toxic to some of the bacteria. This is the first study to demonstrate that microorganisms can biodegrade SF5-substituted aromatic compounds releasing fluoride ion, and biotransform them generating a toxic metabolite.

Whole community transcriptome of a sequencing batch reactor transforming 2,4-dinitroanisole (DNAN) and 3-nitro-1,2,4-triazol-5-one (NTO)

Abstract: Two sequencing batch reactors (SBRs) were run to bio-mineralize 2,4-dinitroanisole (DNAN) and 3-nitro-1,2,4-triazol-5-one (NTO) in lab scale settings. The reactors were shown to reproducibly biotransform these munitions under aerobic and anaerobic conditions during the operations of these SBRs. Complete removal (100% biotransformation) of DNAN (initially 17.7 ± 5.4 mg L-1) and NTO (initially 15.0 ± 7.1 mg L-1) was observed in an anaerobic SBR when Luria-Bertani (LB) broth was present. In contrast, an aerobic SBR degraded only 58 ± 22% of DNAN (initially 19.7 ± 6.2 mg L-1) and 45 ± 24% of NTO (initially 9.7 ± 6.3 mg L-1) when either LB or glucose was also added indicating that anaerobic conditions are more favorable for biotransformation of these munitions. Transcriptomic analysis of the DNAN and NTO degrading anaerobic SBR revealed upregulation of a putative nitroreductase, hydroxylaminophenol mutases, 4-hydroxylphenyl acetate associated genes, and quinone oxioreductases. Major Bacterial populations included Bacteroidales, Campylobacterales, Enterobacteriales, Pseudomonadales, Burkholderiales and Clostridiales. Results from this study can be used to inform investigation of munition degrading organisms and the functional genes responsible.

Anaerobic biodegradation of partially hydrolyzed polyacrylamide in long-term methanogenic enrichment cultures from production water of oil reservoirs

Abstract: The increasing usage of partially hydrolyzed polyacrylamide (HPAM) in oilfields as a flooding agent to enhance oil recovery at so large quantities is an ecological hazard to the subsurface ecosystem due to persistence and inertness. Biodegradation of HPAM is a potentially promising strategy for dealing with this problem among many other methods available. To understand the responsible microorganisms and mechanism of HPAM biodegradation under anaerobic conditions, an enrichment culture from production waters of oil reservoirs were established with HPAM as the sole source of carbon and nitrogen incubated for over 328 days, and analyzed using both molecular microbiology and chemical characterization methods. Gel permeation chromatography, High-pressure liquid chromatography and Fourier-transformed infrared spectroscopy results indicated that, after 328 days of anaerobic incubation, some of the amide groups on HPAM were removed and released as ammonia/ammonium and carboxylic groups, while the carbon backbone of HPAM was converted to smaller polymeric fragments, including oligomers and various fatty acids. Based on these results, the biochemical process of anaerobic biodegradation of HPAM was proposed. The phylogenetic analysis of 16S rRNA gene sequences retrieved from the enrichments showed that Proteobacteria and Planctomycetes were the dominant bacteria in the culture with HPAM as the source of carbon and nitrogen, respectively. For archaea, Methanofollis was more abundant in the anaerobic enrichment. These results are helpful for understanding the process of HPAM biodegradation and provide significant insights to the fate of HPAM in subsurface environment and for possible bioremediation.

Simultaneous removal of hexavalent chromium and o-dichlorobenzene by isolated Serratia marcescens ZD-9

Abstract: Heavy metals–organics mixture pollution is increasingly concerned and simultaneous removal of organic pollutants and heavy metals is becoming significant. In this study, a strain was isolated from the sediment of a tannery effluent outfalls, which can remove o-dichlorobenzene (o-DCB) and Cr(VI) simultaneously. The bacterial isolate was identified as Serratia marcescens by the 16S rRNA gene sequences. The strain removed about 90% of o-DCB and more than 80% of Cr(VI) at the concentration of 1.29 g L−1 o-DCB and 20 mg L−1 Cr(VI). In the presence of concomitant pollutant o-DCB, the optimal pH (8.0) and temperature (30 °C) were determined for Cr(VI) removal. Changes of the bacterial cells and intracellular black Cr(III) sediments were observed by the TEM auxiliary analysis. The results of the FTIR spectroscopy analysis indicated that hydroxyl, amide and polysaccharides were involved in the process of Cr(VI) removal.

Evaluating the mycostimulation potential of select carbon amendments for the degradation of a model PAH by an ascomycete strain enriched from a superfund site.

Abstract: Although ecological flexibility has been well documented in fungi, it remains unclear how this flexibility can be exploited for pollutant degradation, especially in the Ascomycota phylum In this work, we assess three mycostimulation amendments for their ability to induce degradation in Trichoderma harzanium, a model fungus previously isolated from a Superfund site contaminated with polycyclic aromatic hydrocarbons The amendments used in the present study were selected based on the documented ecological roles of ascomycetes Chitin was selected to simulate the parasitic ecological role while cellulose and wood were selected to mimic bulk soil and wood saprobic conditions, respectively Each amendment was tested in liquid basal medium in 01 and 1% (w/v) suspensions Both chitin and cellulose amendments were shown to promote anthracene degradation in T harzanium with the 01% chitin amendment resulting in over 90% removal of anthracene None of the targets monitored for gene expression were found to be upregulated suggesting alternate pathways may be used in T harzanium Overall, our data suggest that mycostimulation amendments can be improved by understanding the ecological roles of indigenous fungi However, further research is needed to better estimate specific amendment requirements for a broader group of target fungi and follow up studies are needed to determine whether the trends observed herein translate to more realistic soil systems

Novel MBR_based main stream biological nutrient removal process: high performance and microbial community

Abstract: For municipal wastewater treatment, main stream biological nutrient removal (BNR) process is becoming more and more important. This lab-scale study, novel MBR_based BNR processes (named A2N-MBR and A2NO-MBR) were built. Comparison of the COD removal, results obtained demonstrated that COD removal efficiencies were almost the same in three processes, with effluent concentration all bellowed 30 mg L−1. However, the two-sludge systems (A2N-MBR and A2NO-MBR) had an obvious advantage over the A2/O for denitrification and phosphorus removal, with the average TP removal rates of 91.20, 98.05% and TN removal rates of 73.00, 79.49%, respectively, higher than that of 86.45 and 61.60% in A2/O process. Illumina Miseq sequencing revealed that Candidatus_Accumulibacter, which is capable of using nitrate as an electron acceptor for phosphorus and nitrogen removal simultaneously, was the dominant phylum in both A2N-MBR and A2NO-MBR process, accounting for 28.74 and 23.98%, respectively. Distinguishingly, major organism groups related to nitrogen and phosphorus removal in A2/O system were Anaerolineaceae_uncultured, Saprospiraceae_uncultured and Thauera, with proportions of 11.31, 8.56 and 5.00%, respectively. Hence, the diversity of dominant PAOs group was likely responsible for the difference in nitrogen and phosphorus removal in the three processes.