Anaerobic Microbial Degradation Research Articles

Assessing anaerobic microbial degradation rates of crude light oil with reverse stable isotope labelling and community analysis

Oil reservoirs represent extreme environments where anaerobic degradation profoundly influences oil composition and quality. Despite the common observation of biodegraded oil, the microbial degradation rates remain largely unknown. To address this knowledge gap, we conducted microcosm incubations with light oil as carbon source, original formation water and sulfate as electron acceptor, closely mimicking in situ conditions to assess oil degradation rates. Samples were taken from a newly drilled oil well to exclude contamination with injection water and allochthonous microorganisms. At the end of the incubations, microbial community analyses with 16S rRNA gene amplicon sequencing revealed the most prominent phyla as Desulfobacterota, Thermotogota, Bacteroidota, Bacillota (formerly Firmicutes), and Synergistota, collectively accounting for up to 44% of relative abundance. Ion chromatography and reverse stable isotope labeling were used to monitor sulfate reduction and CO2 evolution respectively. We calculated an average degradation rate of 0.35 mmol CO2 per year corresponding to 15.2 mmol CO2/mol CH2(oil) per year. This resembles to approximately 200 years to degrade one gram of oil under the applied, presumably ideal conditions. Factoring in the available oil-water-contact (OWC) zone within the incubations yielded a degradation rate of 120 g CH2 m−2 OWC per year, closely aligning with the modeled degradation rates typically observed in oil reservoirs. Moreover, our study highlighted the utility of the reverse stable isotope labeling (RSIL) approach for measuring complex substrate degradation at minute rates.

Bioelectrochemically enhanced biomethane production from low-rank coal using multiple microbial strains

Although microbial in-situ gasification of coal has been established to be an environmentally friendly and sustainable mining method, the low efficiency of methane production via coal micro-gasification limits the commercial applicability of this technology. In this regard, the application of electric fields can contribute to enhancing the efficiency of anaerobic microbial coal degradation. In this study, to investigate the effects of low-intensity electric fields on coal degradation by different exogenous microbial species, we conducted laboratory-scale batch anaerobic fermentation experiments at 0.9, 1.5, and 2.2 V using a micro-gas measuring device to quantify biogas production. The results revealed that application of a low-intensity electric field can promote the production of methane by different microbes, with the highest gas production (7.92 mL/g) obtained at 1.5 V, representing an increase of 131.58 % compared with fermentation conducted in the absence of an applied electric field. The electrodes facilitated the microbial utilization or dissolution of organic matter on the coal surface, leading to a reduction in surface functional groups, with the fermentation medium mainly comprising aromatic hydrocarbons. The coal particles at the anode appeared rough. Collectively, our findings in this study revealed that the application of electric fields contributed to a modification of microbial metabolism and promoted an enhancement of methane production. We believe these findings have important implications for enhancing the microbial production of biomethane from coal.

Anaerobic biodegradation of phenanthrene and pyrene by sulfate-reducing cultures enriched from contaminated freshwater lake sediments

Our current understanding of the susceptibility of hazardous polycyclic aromatic hydrocarbons (PAHs) to anaerobic microbial degradation is very limited. In the present study, we obtained phenanthrene- and pyrene-degrading strictly anaerobic sulfate-reducing enrichments using contaminated freshwater lake sediments as the source material. The highly enriched phenanthrene-degrading culture, MMKS23, was dominated (98%) by a sulfate-reducing bacterium belonging to the genus Desulfovibrio. While Desulfovibrio sp. was also predominant (79%) in the pyrene-degrading enrichment culture, MMKS44, an anoxygenic purple non-sulfur bacterium, Rhodopseudomonas sp., constituted a significant fraction (18%) of the total microbial community. Phenanthrene or pyrene biodegradation by the enrichment cultures was coupled with sulfate reduction, as evident from near stoichiometric consumption of sulfate and accumulation of sulfide. Also, there was almost complete inhibition of substrate degradation in the presence of an inhibitor of sulfate reduction, i.e., 20 mM MoO42−, in the culture medium. After 180 days of incubation, about 79.40 μM phenanthrene was degraded in the MMKS23 culture, resulting in the consumption of 806.80 μM sulfate and accumulation of 625.80 μM sulfide. Anaerobic pyrene biodegradation by the MMKS44 culture was relatively slow. About 22.30 μM of the substrate was degraded after 180 days resulting in the depletion of 239 μM sulfate and accumulation of 196.90 μM sulfide. Biodegradation of phenanthrene by the enrichment yielded a metabolite, phenanthrene-2-carboxylic acid, suggesting that carboxylation could be a widespread initial step of phenanthrene activation under sulfate-reducing conditions. Overall, this novel study demonstrates the ability of sulfate-reducing bacteria (SRB), dwelling in contaminated freshwater sediments to anaerobically biodegrade three-ringed phenanthrene and highly recalcitrant four-ringed pyrene. Our findings suggest that SRB could play a crucial role in the natural attenuation of PAHs in anoxic freshwater sediments.

Development of an in vitro method for activation of X-succinate synthases for fumarate hydroalkylation

Anaerobic microbial degradation of hydrocarbons is often initiated through addition of the hydrocarbon to fumarate by enzymes known as X-succinate synthases (XSSs). XSSs use a glycyl radical cofactor, which is installed by an activating enzyme (XSS-AE), to catalyze this carbon-carbon coupling reaction. The activation step, although crucial for catalysis, has not previously been possible invitro because of insolubility of XSS-AEs. Here, we take a genome mining approach to find an XSS-AE, a 4-isopropylbenzylsuccinate synthase (IBSS)-AE (IbsAE) that can be solubly expressed in Escherichia coli. This soluble XSS-AE can activate both IBSS and the well-studied benzylsuccinate synthase (BSS) invitro, allowing us to explore XSSs biochemically. To start, we examine the role of BSS subunits and find that the beta subunit accelerates the rate of hydrocarbon addition. Looking forward, the methodology and insight gathered here can be used more broadly to understand and engineer XSSs as synthetically useful biocatalysts.

Control Mechanism of Microbial Degradation on the Physical Properties of a Coal Reservoir

This study addressed the effect of microbial methane production on the physical properties of a coal reservoir. Two kinds of coal samples before and after anaerobic degradation were tested by a low-temperature liquid nitrogen adsorption test and an isothermal adsorption and diffusion coefficient test. The influence of the characteristics of microbial gas production on the coal physical properties was analyzed. Due to the differences in the physical properties of the coal samples, the effect of microbial production is different. Coal is a macromolecular organic compound, mainly aromatic and lignin derivatives, containing carbon and nitrogen sources that can be used by microorganisms. Microorganisms secrete extracellular enzymes to decompose covalent bonds and functional groups of macromolecules in coal and eventually produce methane, which will change the physical properties of coal. It was found that microbial anaerobic degradation could increase the content of coalbed methane, change the pore structure of coal, reduce the fractal dimension of the coal surface and smooth the coal surface. At the same time, microbial degradation has changed the physical properties of coal reservoirs to some extent, increased the diffusion of coal reservoirs and improved the pore connectivity of coal reservoirs, which provides more of a scientific basis for the development of coalbed methane.

Anaerobic digestion of hydrothermally pretreated dewatered sewage sludge: effects of process conditions on methane production and the fate of phosphorus.

The hydrothermal pretreatment (HTP) characteristics and the fate of phosphorus (P) and anaerobic digestion (AD) performance of dewatered sewage sludge (DSS) were investigated at different hydrothermal conditions. The maximum methane yield reached 241mL CH4/g COD when the hydrothermal conditions were 200°C-2h-10% (A4), and the yield was 78.28% higher than that without pretreatment (A0) and 29.62% higher than that of the initial hydrothermal conditions (A1, 140°C-1h-5%). Proteins, polysaccharides, and volatile fatty acids (VFAs) were the main hydrothermal products of DSS. 3D-EEM analysis revealed that tyrosine, tryptophan proteins, and fulvic acids decreased after HTP, but the content of humic acid-like substances increased, and this phenomenon was more noticeable after AD. Solid-organic P was converted into liquid-P during the hydrothermal process, and nonapatite inorganic P was converted into organic P during AD. All samples achieved positive energy balance, and the energy balance of A4 was 10.50kJ/g VS. Microbial analysis showed that the composition of the anaerobic microbial degradation community changed as the sludge organic composition was altered. Results showed that the HTP improved the anaerobic digestion of DSS.

Sustained anaerobic degradation of 4-chloro-2-methylphenoxyacetic acid by acclimated sludge in a continuous-flow reactor

4-Chloro-2-methylphenoxyacetic acid (MCPA) is a widely used herbicide across the world. MCPA is persistent and easily transports into anoxic environment, such as groundwater, sediments and deep soils. However, little research on anaerobic microbial degradation of MCPA was carried out. The functional microorganisms as well as the catabolic pathway are still unknown. In this research, an anaerobic MCPA-degrading bacterial consortium was enriched from the river sediment near a pesticide-manufacturing plant. After about 6 months’ acclimation, the MCPA transformation rate of the consortium reached 4.32 μmol g−1 day−1, 25 times faster than that of the original sludge. 96% of added MCPA (2.5 mM) was degraded within 9 d of incubation. Three metabolites including 4-chloro-2-methylphenol (MCP), 2-methylphenol (2-MP) and phenol were identified during the anaerobic degradation of MCPA. An anaerobic catabolic pathway was firstly proposed: firstly, MCPA was transformed to MCP via the cleavage of the aryl ether, then MCP was reductively dechlorinated to 2-MP which was further demethylated to phenol. The 16S rRNA gene amplicon sequencing revealed a substantial shift in the bacterial community composition after the acclimation. SBR1031, Acidaminococcaceae, Aminicenantales, Syntrophorhabdus, Acidaminobacter, Bacteroidetes_vadinHA17, Methanosaeta, Bathyarchaeia, KD4-96, Anaeromyxobacter, and Dehalobacter were significantly increased in the enriched consortium after acclimation, and positively correlated with the anaerobic degradation of MCPA as suggested by heat map correlation analysis. This study provides a basis for further elucidation of the anaerobic catabolism of MCPA, and contributes to developing efficient and low-cost anaerobic treatment technologies for MCPA pollution.

Effect of wine pomace extract on dechlorination of chloroethenes in soil suspension

Chloroethenes are widely used as solvent in the metal industry and the dry cleaning industry, but their spillage into soil and groundwater due to improper handling has negatively impacted human health. Bioremediation using microorganisms is one of the technologies to clean up soil and groundwater contaminated with chloroethenes. In this study, we examined the bioremediation of chloroethene-contaminated soil using wine pomace extract (WPE). WPE is a liquid containing seven major carboxylic acids and other substances extracted from grape pomace produced in winemaking. WPE clearly promoted the anaerobic bioremediation of chloroethenes. In the tetrachloroethene (PCE) degradation test that used fractions derived from WPE, the water-eluted fraction containing l-lactic acid, l-tartaric acid, and others promoted the dechlorination of PCE, whereas the methanol-eluted fraction containing mainly syringic acid did not. In another PCE degradation test that used l-lactic acid, l-tartaric acid, and syringic acid test solutions, l-lactic acid and l-tartaric acid enhanced the dechlorination of PCE, but syringic acid did not. The results suggest that l-lactic acid and l-tartaric acid in WPE function as hydrogen donors in the anaerobic microbial degradation of chloroethene. This technology realizes environmental remediation through the effective use of food by-products.Graphical

Mechanistic characterization of anaerobic microbial degradation of BTBPE in coastal wetland soils: Implication by compound-specific stable isotope analysis

As a novel brominate flame retardants, 1,2-bis(2,4,6-tribromophenoxy)ethane (BTBPE) has been extensively used in various consumer products, and frequently detected in various environmental matrices. However, the microbial degradation of BTBPE remains unclear in the environment. This study comprehensively investigated the anaerobic microbial degradation of BTBPE and therein stable carbon isotope effect in the wetland soils. BTBPE degradation followed the pseudo-first-order kinetic, with degradation rate of 0.0085 ± 0.0008 day−1. Based on identification of degradation products, stepwise reductive debromination was the main transformation pathway of BTBPE, and tended to keep the stable of 2,4,6-tribromophenoxy group during the microbial degradation. The pronounced carbon isotope fractionation was observed for BTBPE microbial degradation, and carbon isotope enrichment factor (εC) was determined to be −4.81 ± 0.37‰, indicating cleavage of C–Br bond as the rate-limiting step. Compared to previously reported isotope effects, carbon apparent kinetic isotope effect (AKIEC = 1.072 ± 0.004) suggested that the nucleophilic substitution (SN2 reaction) was the potential reaction mechanism for reductive debromination of BTBPE in the anaerobic microbial degradation. These findings demonstrated that BTBPE could be degraded by the anaerobic microbes in wetland soils, and the compound-specific stable isotope analysis was a robust method to discover the underlying reaction mechanisms.

Systematic characterization of sediment microbial community structure and function associated with anaerobic microbial degradation of PBDEs in coastal wetland

As the widely used flame retardant, polybrominated diphenyl ethers (PBDEs) have been ubiquitously detected in wetland sediments. Microbial degradation is the importantly natural attenuation process for PBDEs in sediments. In this study, the microbial degradation of PBDEs and inherent alternation of microbial communities were explored in anaerobic sediments from coastal wetland, North China. BDE-47 and BDE-153 could be degraded by the indigenous microbes, with biodegradation following pseudo-first-order kinetic. In sediments, the major genera for BDE-47 and BDE-153 degradation were Paeisporosarcina and Gp7, respectively, in single exposure. However, Marinobacter was dominant genera in the combined exposure to BDE-47 and BDE-153, and competition against Marinobacter existed between BDE-47 and BDE-153 degradation. Analysis of bacterial metabolic function indicated that membrane transport, amino acid and carbohydrate metabolism were included in degradation. This study provides the systematic characterization of the sediment microbial community structure and function associated anaerobic microbial degradation of PBDEs in coastal wetland.

The kinetic reaction of anaerobic microbial chloerobenzenes degradation in contaminated soil

The kinetic reactions of hexachlorobenzene (HCB) and coexisting chlorobenzene congeners in real HCB-contaminated soil and effects of environmental factors on degradation rate, such as solid-liquid ratio, pH and incubation temperatures, were investigated. The Monod model was adopted for the kinetic study and the related kinetic parameters were evaluated. The Monod model showed good fitness for HCB degradation, not for coexisting chlorobenzene congeners. For pentachlorobenzene (PeCB), 1,2,4,5-tetrachlorobenzene(1,2,4,5-TeCB) and 1,2,4-trichlorobenzene(1,2,4-TCB), the calculated value of average degradation rate may not be “positive” or “negative” invariably, depending on production and degradation of these halogenated organic compounds. For HCB, a maximum degradation rate constant of 0.0359 d−1 and half-life time of 19.3 d were achieved, respectively. The hydrogen ion played the most important role in degradation of four chlorobenzenes. However, this role could be weakened if the solubility of compound was considered. Also, the results showed that the initial weak acid to neutral pH (5 – 7) environment with the incubation temperature of 45 °C was favorable for the rapid kinetic degradation of chlorobenzenes and the removal of chlorobenzenes was evaluated to reach 46%. This study offers direct kinetic behaviors and environmental factors analysis of the biodegradation process of HCB and coexisting chlorobenzene congeners, and is beneficial to explored the potential of optimized anaerobic microbial degradation for remediation engineering of chlorobenzenes contained soil.

Microbial production of toluene in oxygen minimum zone waters in the Humboldt Current System off Chile

Expansion of oxygen minimum zones in the world's oceans is likely to enhance the production of anaerobic metabolites by marine microorganisms. Here we show that toluene is present throughout the year in shelf waters of the upwelling ecosystem off Concepción (36° S), Chile, and it is a product of microbial anaerobic metabolism. The intra-annual variability in toluene concentrations is consistent with seasonal variability in the strengths of suboxic equatorial and oxygenated subantarctic water masses. Laboratory incubations of oxygen minimum zone water showed microbial production of toluene in the absence of O2. Toluene concentrations were elevated (up to 96 nM) in deeper O2-depleted waters and followed a seasonal pattern in oceanographic conditions. There is evidence to hypothesize that microbial production of toluene could be a homeostatic biochemical mechanism to thrive in the more acidic oxygen minimum zone waters. On the other hand, evidence indicates that microbial anaerobic degradation of toluene may be a source of NO2− by partial denitrification, as shown for aquifer sediments. Since toluene production was not detected in incubations under aerobic conditions, we hypothesize that oxygen minimum zone waters export toluene to surrounding oxygenated waters. Expansion of hypoxia in the ocean will certainly enhance the production and export of anaerobic metabolites by marine microorganisms.

Diffusion of H2 S from anaerobic thiolated ligand biodegradation rapidly generates bioavailable mercury.

Methylmercury is a potent neurotoxin that biomagnifies through food webs and which production depends on anaerobic microbial uptake of inorganic mercury (Hg) species. One outstanding knowledge gap in understanding Hg methylation is the nature of bioavailable Hg species. It has become increasingly obvious that Hg bioavailability is spatially diverse and temporally dynamic but current models are mostly built on single thiolated ligand systems, omitting ligand exchanges and interactions, or the inclusion of dissolved gaseous phases. In this study, we used a whole-cell anaerobic biosensor to determine the role of a mixture of thiolated ligands on Hg bioavailability. Serendipitously, we discovered how the diffusion of trace amounts of exogenous biogenic H2 S, originating from anaerobic microbial ligand degradation, can alter Hg speciation - away from H2 S production site - to form bioavailable species. Regardless of its origins, H2 S stands as a mobile mediator of microbial Hg metabolism, connecting spatially separated microbial communities. At a larger scale, global planetary changes are expected to accelerate the production and mobilization of H2 S and Hg, possibly leading to increased production of the potent neurotoxin; this work provides mechanistic insights into the importance of co-managing biogeochemical cycle disruptions.

The Kinetic Reaction of Anaerobic Microbial Chloerobenzenes Degradation in Contaminated Soil

The Kinetic Reaction of Anaerobic Microbial Chloerobenzenes Degradation in Contaminated Soil

Application of dual carbon-bromine stable isotope analysis to characterize anaerobic micro-degradation mechanisms of PBDEs in wetland bottom-water

Polybrominated diphenyl ethers (PBDEs), one kind of persistent organic pollutants, were widely detected in coastal wetlands. Microbial reductive debromination is one of the most important attenuation processes for PBDEs in anaerobic environment, whereas the underlying reaction mechanisms remain elusive. Dual-element stable isotope analysis was recently recognized to distinguish different reaction mechanism for degradation of organic pollutants. In this study, the dual carbon-bromine isotope effects associated with the anaerobic microbial degradation were first investigated to characterize the reaction mechanisms for BDE-47 and BDE-153. Presence of lower brominated congeners indicated stepwise debromination as the main degradation pathway, with the preferential removal of bromine in para position > meta/ortho position. The pronounced isotope fractionation was observed for both carbon and bromine, with similar carbon (εC) and bromine isotope enrichment factor (εBr) between BDE-47 (εC = -5.98‰, εBr = -2.44‰) and BDE-153 (εC = -5.57‰, εBr = -2.06‰) during the microbial degradation. Compared to εC and εBr, the correlation of carbon and isotope effects (ΛC/Br = Δδ81Br/Δδ13C) was almost the same between BDE-47 (0.436) and BDE-153 (0.435), indicating the similar reaction mechanism. The calculated carbon and bromine apparent kinetic isotope effects (AKIEC and AKIEBr) were 1.0773 and 1.0098 for BDE-47 and 1.0716 and 1.0125 for BDE-153, within range reported for degradation of halogenated compounds following nucleophilic substitution. Combination analysis of degradation products, ΛC/Br and AKIE, all the results pointed to that the anaerobic reductive debromination of BDE-47 and BDE-153 followed the nucleophilic aromatic substitution, with the addition of cofactor to the benzene ring concomitant with dissociation of carbon-bromine bond via the inner-sphere electron transfer, and the cleavage of C-Br bond was the rate-determining step. This study contributed to the development of dual carbon-bromine isotope analysis as a robust approach to probe the fate of PBDEs in contaminated sites.

The influence of lipid content and taxonomic affiliation on methane and carbon dioxide production from phytoplankton biomass in lake sediment

AbstractThe greenhouse gases methane (CH4) and carbon dioxide (CO2) are end products of microbial anaerobic degradation of organic matter (OM) in lake sediments. Although previous research has shown that phytoplankton lipid content influences sediment methanogenesis, current understanding on how OM quality affects methanogenesis is still limited. Such information is needed to more accurately assess how lake greenhouse gas emissions may change in response to anthropogenic activities. We cultured 11 phytoplankton species from five classes and studied how taxonomic identity, C : N ratio, lipid content, and fatty acid composition of phytoplankton biomass affects the CH4 and net CO2 production in anaerobic lake sediments with an incubation experiment that lasted > 100 d. The carbon‐normalized potential CH4 (0.09–0.23 μmol mg C−1 d−1) and net CO2 (0.09–0.28 μmol mg C−1 d−1) production rates were not related to phytoplankton taxonomic affiliation (e.g., class, species), C : N ratio, or fatty acid composition of algal biomass. Methane or net CO2 production potentials did not increase with higher lipid content (10–30%); however, total fatty acid content had a weak correlation with CH4 production potential. In contrast to previous research, our results suggest that lipid content is of minor importance in determining methanogenesis rates from the biomass of multispecies phytoplankton communities settling on sediments. The decrease in CO2 concentration and the correlation between stable carbon isotope signatures of CH4 and molar ratio of CH4 and CO2 at the end of the experiment may indicate that importance of hydrogenotrophic methanogenesis, which uses CO2 when other substrates become limiting, increased during the long incubation.

Removal efficiency, kinetic, and behavior of antibiotics from sewage treatment plant effluent in a hybrid constructed wetland and a layered biological filter

Sewage treatment plant (STP) is the major point source of antibiotic contamination, yet the advanced treatment of antibiotic polluted STP effluent has not been given necessary attention. This study is conducted to evaluate the removal efficiency, kinetic, and behavior of sulfonamides, quinolones, tetracyclines, and macrolides antibiotics from STP effluent in a hybrid constructed wetland (HCW) and a layered biological filter (LBF) at different hydraulic loading rates (HLRs). The results showed that the removal efficiency of antibiotics in all the HLRs was ranked as follow: quinolones of HCW (70–95%) > macrolides of HCW (58–77%) > tetracyclines of both systems (59–67%) > quinolones of LBF (28–64%) > macrolides of LBF (13–25%) > sulfonamides of both systems (<0%). The optimal HLR is 1.0 m/day for quinolones and 2.0 m/day for tetracyclines-macrolides in the HCW, and 6.4 m/day for quinolones-tetracyclines in the LBF, respectively. Although HCW performed better on the removal of most antibiotics, LBF exhibited stronger total loading toleration and higher removal loading ability to antibiotics. Among them, quinolones were markedly removed by multiple effect of substrate adsorption, microbial anaerobic degradation, and photolysis in the HCW (planted), and by filter sorption and interception in the LBF (unplanted); adsorption is the dominant elimination approach for tetracyclines in both systems; plant uptake plays a significant role on the removal of macrolides in the HCW.

Enzymatic C–H activation of aromatic compounds through CO2 fixation

The direct C-H carboxylation of aromatic compounds is an attractive route to the corresponding carboxylic acids, but remains challenging under mild conditions. It has been proposed that the first step in anaerobic microbial degradation of recalcitrant aromatic compounds is a UbiD-mediated carboxylation. In this study, we use the UbiD enzyme ferulic acid decarboxylase (Fdc) in combination with a carboxylic acid reductase to create aromatic degradation-inspired cascade reactions, leading to efficient functionalization of styrene through CO2 fixation. We reveal that rational structure-guided laboratory evolution can expand the substrate scope of Fdc, resulting in activity on a range of mono- and bicyclic aromatic compounds through a single mutation. Selected variants demonstrated 150-fold improvement in the conversion of coumarillic acid to benzofuran + CO2 and unlocked reactivity towards naphthoic acid. Our data demonstrate that UbiD-mediated C-H activation is a versatile tool for the transformation of aryl/alkene compounds and CO2 into commodity chemicals.

An LC-MS/MS Method for a Comprehensive Determination of Metabolites of BTEX Anaerobic Degradation in Bacterial Cultures and Groundwater

BTEX (benzene, toluene, ethylbenzene, and the different xylene isomers), known for carcinogenic and neurotoxic effects, are common environmental contaminants. The first step for the development of the bioremediation technologies is the detection of intense microbial degradation in contaminated waters in the quest for the most active bacterial strains. This requires the multispecies analysis for BTEX metabolites which are considered as markers of microbial degradation. A direct (50 µL injection) HPLC–electrospray MS/MS analytical method was developed for the simultaneous analysis of 11 BTEX metabolites (o-, m-, p-toluic, salicylic, benzoate, benzyl, and phenyl succinic acids, 2-(1-phenylethyl)-, 2-(2-methylbenzyl), and 2-(3-methylbenzyl)-, 2-(4-methyl benzyl)-succinic acids) in bacterial cultures and ground waters down to 0.1 ng/mL. The optimization of the chromatographic conditions allowed for the resolution of position isomers of toluic and methylbenzyl-succinic acids. The stability of the analytes during sample storage tested in different conditions showed the instability of some of them when stored at room temperature. The feasibility of the method was demonstrated by the detection of all the investigated metabolites in a water sample of a deep aquifer hosting natural gas storage. A model laboratory study emphasized the importance of 2-(2-methylbenzyl)-succinic acid as a marker of anaerobic microbial degradation.

Influence of particle size distribution on anaerobic degradation of phenol and analysis of methanogenic microbial community.

Sludge morphology considerably affects the mechanism underlying microbial anaerobic degradation of phenol. Here, we assessed the phenol degradation rate, specific methanogenic activity, electron transport activity, coenzyme F420 concentration, and microbial community structure of five phenol-degrading sludge of varying particle sizes (i.e., < 20, 20-50, 50-100, 100-200, and > 200μm). The results indicated an increase in phenol degradation rate and microbial community structure that distinctly correlated with an increase in sludge particle size. Although the sludge with the smallest particle size (< 20μm) showed the lowest phenol degradation rate (9.3mg COD·gVSS-1 day-1), its methanogenic activity with propionic acid, butyric acid, and H2/CO2 as substrates was the best, and the concentration of coenzyme F420 was the highest. The small particle size sludge did not contain abundant syntrophic bacteria or hydrogenotrophic methanogens, but contained abundant acetoclastic methanogens. Moreover, the floc sizes of the different sludge varied in important phenol-degrading bacteria and archaea, which may dominate the synergistic mechanism. This study provides a new perspective on the role of sludge floc size on the anaerobic digestion of phenol.