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PubMed2003

Comparison of diethylene glycol and phenol biodegradability by different test methods.

Biodegradation is generally recognised as an important removal mechanism for pollutants in natural ecosystems. It determines the concentration of substances in the environment. According to the legislation of the European Union, there are three levels for biodegradability testing protocols for chemicals which cover different test conditions. This paper describes one such multilevel approach to biodegradation testing. Four different tests were performed on diethylene glycol and phenol. Diethylene glycol did not fulfill the requirements for ready biodegradable substances, while it degraded well in wastewater treatment plant simulation test. Phenol in turn, resulted ready biodegradable, and its biodegradability depended less on experimental conditions than the biodegradability of diethylene glycol. This corroborates the importance of combining different test methods to obtain relevant biodegradability data.

Biodegradation, Environmental↗

PubMed2006

Biodegradability of tannin-containing wastewater from leather industry.

Tannins occur commonly in the wastewaters from forestry, plant medicine, paper and leather industries. The treatment of this kind of wastewaters, including settling and biodegradation, is usually difficult because tannins are highly soluble in water and would inhibit the growth of microorganisms in activated sludge. The objective of this study is to investigate biodegradability of tannin-containing wastewaters, so as to characterize the pollution properties of such wastewaters and provide a reference for their biological treatment in wastewater treatment plants. The research was typified by using the wastewater collected from vegetable tanning process in leather industry. A model was developed to describe the activated sludge process, and the biodegradation kinetics of vegetable tanning wastewater (VET wastewater) was studied. It was found that the biodegradability of tannin-containing wastewater varies heavily with the content of tannins in wastewater. The biodegradation of VET wastewater with tannin content around 4,900 mg/l occurred inefficiently due to the inhibition of tannins to the activated sludge process, and only 34.7% of biodegradation extent was reached in 14 days of incubation. The optimal biodegradability of VET wastewater was observed when its tannin content was diluted to 490 mg/l, where the COD and tannin removals reached 51.3% and 45.1% respectively in 6 days. Hence, it is suggested that a proper control of tannin content is necessary to achieve an effective biodegradation of tannin-containing wastewaters in wastewater treatment plants.

Kinetics↗

PubMed2004

Chemistry of polymer biodegradation and implications on parenteral drug delivery.

Most polymeric implants are biodegraded by one of two common chemical degradation mechanisms: (i). hydrolysis and (ii). oxidation. The chemical structure is among the most important factors which affect the biodegradation of polymeric implants. Hydrolytic biodegradations are often accompanied by substantial decrease of pH, whilst oxidative biodegradation processes are usually very slow due to consumption of stoichiometric amounts of oxidising agents. A dramatic acceleration of the biodegradation can be expected, if the biodegradation can be initiated by catalytic amounts of oxidation agents. Poly(ethylene carbonate) (PEC) and poly(trimethylene carbonate) (PTMC) are presumably biodegraded by such catalytic oxidation processes. Their biodegradation shows all the characteristics of surface erosion. Poly(ethylene carbonate) is utilised as a surface eroding biocompatible polymer for controlled delivery of peptide and protein drugs.

Animals↗

PubMed2005

An evaluation of the clinical application of three different biodegradable osteosynthesis materials for the fixation of zygomatic fractures.

OBJECTIVE: The aim of this prospective study was to compare the clinical handling of 3 different biodegradable osteosynthesis materials and to determine whether they can be used for the fixation of all types of zygomatic fractures. STUDY DESIGN: A total of 54 consecutive patients who presented with displaced fractures of the zygomatic bone between October 2001 and May 2003 were randomly allocated to 3 biodegradable material groups for the fixation of the fractures. A titanium fixation system was used as rescue osteosynthesis whenever biodegradable materials failed. RESULTS: Seventy-one (75.5%) of 94 fracture sites were fixed with biodegradable osteosynthesis; 23 (24.5%) had to be fixed with titanium plates and screws. No statistically significant difference was found between the 3 biodegradable materials with regard to their suitability for zygomatic fracture fixation (P = .16). Nonstable fixation (n = 7) or the need to fix small fragments (n = 16) were the reasons for using the titanium fixation system as rescue osteosynthesis at these sites. Biodegradable materials were most frequently unfeasible for use at the infraorbital rim and in the zygomaticomaxillary/anterior sinus wall area. CONCLUSIONS: It was possible to stabilize 3 of 4 zygomatic fractures with 1.5- or 1.7-mm biodegradable osteosynthesis. Insufficient fracture stabilization, especially at the infraorbital rim and the zygomaticomaxillary crest/anterior sinus wall, was the main reason to switch to titanium osteosynthesis. The biodegradable screw design is possibly too bulky for these particular bony structures.

Absorbable Implants↗

PubMed2006

Complications after zygoma fracture fixation: is there a difference between biodegradable materials and how do they compare with titanium osteosynthesis?

OBJECTIVE: Biodegradable materials are particularly useful for the fixation of zygomatic fractures. Different systems are commercially available. The aim of this study was to compare the clinical outcome of zygomatic fracture fixation using 3 biodegradable systems and a titanium osteosynthesis system. STUDY DESIGN: Patients with displaced fractures of the zygomatic bone presenting at our department from October 2001 to May 2003 were randomly allocated to 1 of 3 treatment groups for fracture fixation (study group A: LactoSorb: n = 18; study group B: BioSorb: n = 18; study group C: Delta: n = 18). Treatment outcome and complication rates were compared with a historic patient group with zygomatic fractures fixed with titanium osteosynthesis (control group D: n = 15). RESULTS: A total of 64 patients (study groups A + B + C: n = 49; control group D: n = 15) were followed for at least 24 months (range: 24 to 44 months). Forty-nine patients in the biodegradable study groups (group A: n = 15; group B: n = 17; group C: n = 17) who had their fractures fixed with biodegradable plates and screws alone or in combination with titanium plates and screws were reviewed postoperatively. Uneventful healing occurred during the entire follow-up period in 39 (80%) out of 49 patients in the biodegradable groups (A + B + C) and in 12 (80%) out of 15 patients in group D. Ten patients in groups A + B + C developed postoperative complications (infection: n = 3; soft tissue dehiscence: n = 2; implant-related tissue reactions: n = 5), compared with 3 patients in group D (soft tissue dehiscence: n = 1; unspecific pain: n = 2) (P = .97). Complications occurred in 4 patients in group A and 3 patients each in groups B and C. Smokers developed significantly more postoperative complications than nonsmokers in groups A + B + C (P = .01). CONCLUSION: There was no significant difference between biodegradable osteosynthesis materials or between biodegradable materials and titanium fixation with respect to fracture healing and postoperative complications. Postoperative complications were of a minor nature and resolved spontaneously or after local therapy. Smoking habits may play a significant role in the incidence of complications with biodegradable materials.

Absorbable Implants↗

PubMed1990

Biodegradation of Dinoseb (2-sec-Butyl-4,6-Dinitrophenol) in Several Idaho Soils with Various Dinoseb Exposure Histories.

We examined the ability of native microorganisms in various Idaho soils to degrade dinoseb and studied some physical and chemical soil characteristics which might affect the biodegradation process. Dinoseb biodegradation rates were higher in silt-loam soils than in loamy-sand soils. Biodegradation rates were not influenced by previous exposure of the soils to dinoseb. Bacterial numbers, measured by standard plate counts on soil extract agar, were the best predictors of biodegradation rates, accounting for 53% of the variability between soils. Soil nitrate-N inhibited dinoseb biodegradation and accounted for 39% of the variability. Sorption of dinoseb to soil surfaces also appeared to influence biodegradation rates. No other soil parameter contributed significantly to the variability in biodegradation rates. Persistence of dinoseb in one soil was due to inhibition of biodegradation by nitrate, while in another soil persistence appeared to be due to lack of native degradative microorganisms.

Journal Article↗

PubMed2026

Bioplastic biodegradability shapes microbial communities in a coastal brackish environment.

Microorganisms are metabolically versatile and central to marine ecosystems, yet the potential of marine microbial communities to degrade different bioplastics and the effect of environmental factors are poorly understood. Employing multi-seasonal in situ and in vitro experiments, we assessed the biodegradation of six commonly used bio-based bioplastic materials at a coastal site in the brackish Baltic Sea and characterized the associated microbial communities using metagenomics and metatranscriptomics. Cellulose acetate (CA), polybutylene succinate (PBS), and polyhydroxybutyrate/valerate (PHB) degraded at varying rates across materials, seasons, and experimental settings, with up to 28% weight attrition after 97 weeks in situ (CA) and 56% carbon loss as CO2 after 4 weeks in vitro (PBS). The three biodegraded plastics developed similar microbial communities that differed markedly from those on the other materials (cellulose acetate propionate, polyamide, and polyethylene) and in the water column. The main microbial populations on the biodegraded plastics included aerobic and facultative anaerobic heterotrophs with a broad capacity for carbohydrate metabolism. Populations with the potential for nitrogen fixation and denitrification were more prevalent on the biodegraded plastics, suggesting that bioplastic biodegradation is constrained by and coupled to the marine nitrogen cycle. Based on the metatranscriptomic signal of key genes involved in the initial hydrolysis of CA, PBS, and PHB, we identified diverse microbial populations that can potentially drive the biodegradation of these materials in the Baltic Sea, many of which encoded the potential to degrade multiple bioplastics. We propose the term 'bioplastisphere' to denote the distinctive microbial communities associated with biodegradable plastics.

Seawater↗

PubMed2024

Identification of a putative novel polycyclic aromatic hydrocarbon-biodegrading gene cluster in a marine Roseobacteraceae bacterium Sagittula sp. MA-2.

UNLABELLED: The ability to biodegrade polycyclic aromatic hydrocarbons (PAHs) and the catabolic enzymes responsible for PAH biotransformation in marine bacteria belonging to the family Roseobacteraceae remain largely unexplored despite their wide distribution and highly diverse physiological traits. A bacterial isolate within Roseobacteraceae originating from coastal seawater, Sagittula sp. strain MA-2, that biotransformed phenanthrene and utilized it as a growth substrate was found to possess a putative PAH-degrading gene cluster on one of the eight circular plasmids in its genome. Subsequent comprehensive investigations utilizing bacterial genomes in public databases revealed that gene clusters potentially homologous to this newly found cluster are widely but heterogeneously distributed within Roseobacteraceae and a few non-Roseobacteraceae (Paracoccaceae and Rhizobiaceae) strains from saline environments. Catabolic functions of the enzymes encoded in strain MA-2 were predicted through the profiling of phenanthrene biotransformation products by liquid chromatography-electrospray ionization high-resolution mass spectrometry and substrate docking simulations using predicted three-dimensional structures of selected proteins, and phenanthrene biodegradation pathways were proposed. Strain MA-2 appeared to biodegrade phenanthrene via two separated, concurrent pathways, namely the salicylate and phthalate pathways. This study serves as the first investigation into the functional genes potentially responsible for PAH biodegradation conserved in Roseobacteraceae bacteria, expanding scientific understanding of the physiological repertoire evolved in this ubiquitous marine bacterial group. IMPORTANCE: The ocean is often characterized as the terminal destination for persistent polycyclic aromatic hydrocarbon (PAH) environmental pollutants; however, the ability to biodegrade PAHs and the corresponding enzymes conserved among marine bacteria are less understood compared to their terrestrial counterparts. A marine bacterial isolate, Sagittula sp. strain MA-2, belonging to the family Roseobacteraceae-a widely distributed and physiologically diverse marine bacterial group-was found to possess a functional gene cluster encoding enzymes potentially responsible for PAH biodegradation in its genome and exhibit the ability to biodegrade the three-ring PAH, phenanthrene. Intriguingly, gene clusters potentially homologous to this cluster were also distributed broadly across genomes from different Roseobacteraceae genera in public databases, which has not been previously investigated. The knowledge provided here expands our understanding of the physiology of Roseobacteraceae and may be applied to explore biotechnologically useful bacteria that contribute to the remediation of polluted marine environments or high-salinity wastewater.

Multigene Family↗

PubMed2001

Evaluation of the interaction between biodegradation and sorption of phenanthrene in soil-slurry systems.

This work develops and utilizes a non-steady-state model for evaluating the interactions between sorption and biodegradation of hydrophobic organic compounds in soil-slurry systems. The model includes sorption/desorption of a target compound, its utilization by microorganisms as a primary substrate existing in the dissolved phase, and/or the sorbed phase in biomass and soil, oxygen transfer, and oxygen utilization as an electron acceptor. Biodegradation tests with phenanthrene were conducted in liquid and soil-slurry systems. The soil-slurry tests were performed with very different mass transfer rates: fast mass transfer in a flask test at 150 rpm, and slow mass transfer in a roller-bottle test at 2 rpm. The results of liquid tests indicate that biodegradation of the soil-soluble organic fraction did not significantly enhance the biodegradation rate. In the slurry tests, phenanthrene was degraded more rapidly than in liquid tests, but at a similar rate in both slurry systems. Modeling analyses with several hypotheses indicate that a model without biodegradation of compound sorbed to the soil was not able to account for the rapid degradation of phenanthrene, particularly in the roller-bottle slurry test. The model with sorbed-phase biodegradation and the same biokinetic parameters, but unique mass transfer coefficients, simulated the experimental data in both slurry tests most successfully. Reduced mass transfer resistance to bacteria attached to the soil is the most likely phenomenon accounting for rapid sorbed-phase biodegradation.

Adsorption↗

PubMed2005

Dual substrate biodegradation of a nonionic surfactant and pentachlorophenol by Sphingomonas chlorophenolica RA2.

The simultaneous biodegradation of the nonionic surfactant Tween 20 (Tw20) and pentachlorophenol (PCP) by Sphingomonas chlorophenolica sp. Strain RA2 (RA2) was measured. As a sole substrate, Tw20 biodegradation was best described by the Contois kinetic model. During concurrent biodegradation of Tw20 and PCP, the biodegradation rates of Tw20 were not significantly affected by 50 or 100 mg/L PCP, but were significantly inhibited by 500 mg/L PCP. Decreases in cell yield in the presence of PCP suggest that PCP was acting as an uncoupler. Cultures were pre-grown on PCP or Tw20 before degradation of PCP to evaluate enzyme induction effects, and long lags before PCP biodegradation after growth on Tw20 occurred. Although biokinetic models could accurately describe some of the data sets of RA2 growth and Tw20 and PCP degradation, finding a single set of kinetic parameters that predicted all dual substrate tests was not achieved. The complicating factors to modeling PCP and Tw20 interactions are described and may be more widely applicable to the biodegradation of toxic organic compounds in the presence of a biodegradable surfactant.

Biodegradation, Environmental↗

PubMed1995

Ready biodegradability test in seawater: a new methodological approach.

To estimate the persistence of xenobiotic in the environment, a new ultimate mineralization approach for assessing ready biodegradability in seawater has been developed, based on the OECD 301 B guideline for freshwater. a few changes in the currently accepted procedure have been made to adapt the test to seawater. The assays, realized with seawater as test medium and inoculum, give high variability results of biodegradability. To lower this variability a synthetic marine medium joined to a highly concentrated inoculum from a marine aquarium filter have been used. The results reveal (i) a decrease of variability, together with an increase in degradation rate of the tested chemicals due to a better control of inoculum and test medium, and (ii) no difference in easy biodegradable compound (sodium benzoate) biodegradation rate when two marine aquarium inocula are tested. This study demonstrates that the ready biodegradability test developed on synthetic marine medium and inoculum from marine aquarium filter minimizes the effect of the sample location on the biodegradation results of compounds and allows classifying chemicals as a function of their biodegradability.

Aniline Compounds↗

PubMed1996

Estimating the removal and biodegradation potential of radiolabeled organic chemicals in activated sludge.

A two-step procedure is described to characterize the removal and biodegradation potential of nonvolatile 14C-labeled organic compounds in activated sludge. In the first step, trace concentrations of radiolabeled test materials are dosed in influent wastewater to continuous-flow activated sludge (CAS) systems which have been previously exposed or acclimated to unlabeled test material. Radiolabel is quantified in influent, effluent, and activated sludge mixed liquor to determine total 14C removal and partitioning of radiolabel in solid and liquid compartments. The 14C data are used to calculate the amount of removal due to sorption and biodegradation and to estimate the apparent sorption coefficients for 14C activity to activated sludge solids. The 14C-labeled CAS studies are followed by biodegradation studies in batch-activated sludge (BAS) systems using sludge derived from the CAS system. The kinetics of biodegradation (defined as mineralization to 14CO2) are measured in the BAS system to confirm the CAS biodegradation results and generate mineralization rate constants for kinetic modeling. The two-step procedure was applied to radiolabeled anionic (linear alkylbenzene sulfonate) and cationic (dodecyltrimethylammonium chloride, distearyldimethylammonium chloride) surfactants which differed greatly in their biodegradation and sorption profiles. Laboratory removal figures for these materials were comparable to values measured in full-scale wastewater treatment systems, although the amount of removal due to sorption and biodegradation varied significantly for the different surfactants. In general, the 14C method has several advantages over standard methods used in the United States and Europe which employ unlabeled materials. These advantages include the use of realistic concentrations and test conditions for acclimating and dosing activated sludge microorganisms and the ability to generate partitioning and kinetic constants that can be used more broadly in environmental fate and exposure models.

Biodegradation, Environmental↗

PubMed1988

Biodegradation of hydrocarbons in the environment.

Studies on the environmental fate of petroleum have demonstrated the nearly ubiquitous distribution of microorganisms that can metabolize hydrocarbons. The rates of degradation depend upon the concentrations of such microbes and upon the environmental characteristics of an oil-contaminated ecosystem. Given the appropriate environmental conditions, microorganisms effectively decontaminate, by their biodegradative metabolism, environments that have received petroleum pollutants. Higher-molecular-weight compounds, especially those with multiple condensed ring structures and with highly branched or substituted compounds, are relatively resistant to microbial attack. Despite the fact that a genetically engineered hydrocarbon degrader was the first organism ever patented and that seed cultures are produced by various commercial firms, enhanced biodegradation as a result of seeding generally has not been shown to be effective. Also, even though some anaerobes have now been demonstrated to be capable of hydrocarbon metabolism, hydrocarbons persist indefinitely in anoxic environments. Environmental modification, on the other hand, such as that achieved by aeration or fertilization with nitrogen and phosphorus, has been shown to enhance biodegradative removal of hydrocarbons. Having considered the various factors that influence the rates of hydrocarbon biodegradation, we are left with the question of what to do when environmental oil contamination occurs in order to minimize its persistence and thus its long-term effects. Clearly, treatment methods should enhance rather than inhibit the natural rates of oil biodegradation. In some cases, it is possible to modify environmental parameters to enhance rates of hydrocarbon biodegradation, but such methods are rarely undertaken. The translation of our scientific knowledge of hydrocarbon biodegradation into practical applications remains a major challenge. Specifically designed organisms are needed to degrade toxic aromatic components of refinery waste streams before environmental treatment. Specially designed reactors with specific microbial populations are also needed if oily sludges are to be degraded by biological means, either aerobically or anaerobically, in contained, environmentally safe reactors.

Biodegradation, Environmental↗

PubMed2004

Microbial diversity during biodegradation of crude oil in seawater from the North Sea.

Microbial communities were characterized during biodegradation of immobilized oil in seawater from the Statfjord field and the German Bight in the North Sea. Seawater samples were collected at different distances from pollution sources at the two locations. A Statfjord oil was immobilized on hydrophobic synthetic Fluortex fabrics and submerged in closed flasks (no headspace) with natural or sterile seawater and incubated at 13 degrees C for 56 days. Biodegradation of immobilized n-alkanes was measured by gas chromatography, total microbes were enumerated by epifluorescence microscopy, and culturable heterotrophic and oil-degrading microorganisms were quantified by most probable number (MPN) analysis. Polymerase chain reaction (PCR) amplification of bacterial 16S rDNA in water samples was conducted during biodegradation experiments. The amplified 16S rDNA fragments were characterized by denaturing gradient gel electrophoresis (DGGE), and by sequence analysis of cloned inserts. Biodegradation rates of alkanes in seawater collected at different distances from the pollution sources did not differ significantly (P > 0.05). Concentrations of oil-degrading microorganisms showed a temporary peak after 7 days of degradation, with a subsequent decline later in the period. DGGE analysis of 16S rRNA genes showed that community diversity decreased during the first 2-3 weeks of biodegradation, with the emergence of a few dominant bands. Cloning, restriction analysis, and sequence analysis of the 16S rDNA fragments revealed >30 different phylotypes. Abundant types during biodegradation belonged to the alpha-Proteobacteria, in waters from both Statfjord and the German Bight. Cloning and sequencing studies indicated that the most abundant bacteria during biodegradation belonged to the family Rhodobacteraceae, with the closest relationship to the genera Sulfitobacter and Roseobacter.

Alkanes↗

PubMed2002

The influence of lignin content and temperature on the biodegradation of lignocellulose in composting conditions.

The aim of this research was to study the influence of lignin content and composting temperature on the biodegradation of lignin-containing pulp and paper products in a controlled composting test (European standard prEN 14046). Lignin reduced the biodegradation of the samples, and there was a linear correlation between the lignin content and the biodegradation of pulp and paper products at 58 degrees C. The influence of incubation temperature (35, 50 and 58 degrees C) on biodegradation was studied using bleached kraft paper containing 0.2 wt% lignin and mechanical pulp (stone-ground wood) containing 24-27 wt% lignin. Mechanical pulp biodegraded better at lower temperatures, while kraft paper biodegraded well at all three temperatures. Microbial activity was evaluated by measuring CO(2) evolution and the change in ATP content, and fungal biomass by measuring the ergosterol content during the composting experiments. Kraft paper strongly increased microbial activity during the controlled composting test, but the activity returned to the background level at the end of the composting test. The proportion of sample carbon converted to microbial biomass carbon was considerably higher at lower incubation temperatures. Changes in microbial community structure during biodegradation of mechanical pulp and kraft paper at 50 degrees C were studied by the PCR-based technique denaturing gradient gel electrophoresis. Changes in the microbial community were observed during the intensive degradation phase of kraft paper.

Bacteria↗

PubMed2004

Biodegradation of hydrocarbon cuts used for diesel oil formulation.

The biodegradability of various types of diesel oil (DO), such as straight-run DO, light-cycle DO, hydrocracking DO, Fischer-Tropsch DO and commercial DO, was investigated in biodegradation tests performed in closed-batch systems using two microflorae. The first microflora was an activated sludge from an urban wastewater treatment plant as commonly used in biodegradability tests of commercial products and the second was a microflora from a hydrocarbon-polluted soil with possible specific capacities for hydrocarbon degradation. Kinetics of CO(2) production and extent of DO biodegradation were obtained by chromatographic procedures. Under optimised conditions, the polluted-soil microflora was found to extensively degrade all the DO types tested, the degradation efficiencies being higher than 88%. For all the DOs tested, the biodegradation capacities of the soil microflora were significantly higher than those of the activated sludge. Using both microflora, the extent of biodegradation was highly dependent upon the type of DO used, especially its hydrocarbon composition. Linear alkanes were completely degraded in each test, whereas identifiable branched alkanes such as farnesane, pristane or phytane were degraded to variable extents. Among the aromatics, substituted mono-aromatics were also variably biodegraded.

Biodegradation, Environmental↗

PubMed1997

Thermophilic biodegradation of BTEX by two consortia of anaerobic bacteria.

Two thermophilic anaerobic bacterial consortia (ALK-1 and LLNL-1), capable of degrading the aromatic fuel hydrocarbons, benzene, toluene, ethylbenzene, and the xylenes (BTEX compounds), were developed at 60 degrees C from the produced water of ARCO'S Kuparuk oil field at Alaska and the subsurface water at the Lawrence Livermore National Laboratory gasoline-spill site, respectively. Both consortia were found to grow at 45-75 degrees C on BTEX compounds as their sole carbon and energy sources with 50 degrees C being the optimal temperature. With 3.5 mg total BTEX added to sealed 50-ml serum bottles, which contained 30 ml mineral salts medium and the consortium, benzene, toluene, ethylbenze, m-xylene, and an unresolved mixture of o- and p-xylenes were biodegraded by 22%, 38%, 42%, 40%, and 38%, respectively, by ALK-1 after 14 days of incubation at 50 degrees C. Somewhat lower, but significant, percentages of the BTEX compounds also were biodegraded at 60 degrees C and 70 degrees C. The extent of biodegradation of these BTEX compounds by LLNL-1 at each of these three temperatures was slightly less than that achieved by ALK-1. Use of [ring-14C]toluene in the BTEX mixture incubated at 50 degrees C verified that 41% and 31% of the biodegraded toluene was metabolized within 14 days to water-soluble products by ALK-1 and LLNL-1, respectively. A small fraction of it was mineralized to 14CO2. The use of [U-14C]benzene revealed that 2.6%-4.3% of the biodegraded benzene was metabolized at 50 degrees C to water-soluble products by the two consortia; however, no mineralization of the degraded [U-14C]benzene to 14CO2 was observed. The biodegradation of BTEX at all three temperatures by both consortia was tightly coupled to sulfate reduction as well as H2S generation. None was observed when sulfate was omitted from the serum bottles. This suggests that sulfate-reducing bacteria are most likely responsible for the observed thermophilic biodegradation of BTEX in both consortial cultures.

Bacteria, Anaerobic↗

PubMed2005

Enhanced anaerobic biodegradation of BTEX-ethanol mixtures in aquifer columns amended with sulfate, chelated ferric iron or nitrate.

Flow-through aquifer columns were used to investigate the feasibility of adding sulfate, EDTA-Fe(III) or nitrate to enhance the biodegradation of BTEX and ethanol mixtures. The rapid biodegradation of ethanol near the inlet depleted the influent dissolved oxygen (8 mg l(-1)), stimulated methanogenesis, and decreased BTEX biodegradation efficiencies from > 99% in the absence of ethanol to an average of 32% for benzene, 49% for toluene, 77% for ethylbenzene, and about 30% for xylenes. The addition of sulfate, EDTA-Fe(III) or nitrate suppressed methanogenesis and significantly increased BTEX biodegradation efficiencies. Nevertheless, occasional clogging was experienced by the column augmented with EDTA-Fe(III) due to iron precipitation. Enhanced benzene biodegradation (> 70% in all biostimulated columns) is noteworthy because benzene is often recalcitrant under anaerobic conditions. Influent dissolved oxygen apparently played a critical role because no significant benzene biotransformation was observed after oxygen was purged out of the influent media. The addition of anaerobic electron acceptors could enhance BTEX biodegradation not only by facilitating their anaerobic biodegradation but also by accelerating the mineralization of ethanol or other substrates that are labile under anaerobic conditions. This would alleviate the biochemical oxygen demand (BOD) and increase the likelihood that entraining oxygen would be used for the biotransformation of residual BTEX.

Aerobiosis↗