Effect of Carbon and Energy Source on Bacterial Chromate Reduction

Studies were conducted to evaluate carbon and energy sources suitable to support hexavalent chromium (Cr(VI)) reduction by a bacterial consortium enriched from dichromate-contaminated aquifer sediments. The consortium was cultured under denitrifying conditions in a minimal, synthetic groundwater medium that was amended with various individual potential carbon and energy sources. The effects of these individual carbon and energy sources on Cr(VI) reduction and growth were measured. The consortium was found to readily reduce Cr(VI) with sucrose, acetate, L-asparagine, hydrogen plus carbon dioxide, ethanol, glycerol, glycolate, propylene glycol, or D-xylose as a carbon and energy source. Minimal Cr(VI) reduction was observed when the consortium was cultured with citrate, 2-ketoglutarate, L-lactate, pyruvate, succinate, or thiosulfate plus carbon dioxide as a carbon and energy source when compared with abiotic controls. The consortium grew on all of the above carbon and energy sources, with the highest cell densities reached using D-xylose and sucrose, demonstrating that the consortium is metabolically diverse and can reduce Cr(VI) using a variety of different carbon and energy sources. The results suggest that the potential exists for the enrichment of Cr(VI)-reducing microbial populations in situ by the addition of a sucrose-containing feedstock such as molasses, which is an economical and readily available carbon and energy source.     

Biodegradation of coumaphos, chlorferon, and diethylthiophosphate using bacteria immobilized in Ca-alginate gel beads

Calcium-alginate immobilized cell systems were developed for the detoxification and biodegradation of coumaphos, an organophosphate insecticide, and its hydrolysis products, chlorferon and diethlythiophosphate (DETP). Optimum bead loadings for bioreactor operation were found to be 200 g-beads/L for chlorferon degradation and 300 g-beads/L for DETP degradation. Using waste cattle dip (UCD) solution as substrate, the degradation rate for an immobilized consortium of chlorferon-degrading bacteria was five times greater than that for freely suspended cells, and hydrolysis of coumaphos by immobilized OPH(+)Escherichia coli was 2.5 times greater. The enhanced degradation of immobilized cells was due primarily to protection of the cells from inhibitory substances present in the UCD solution. In addition, physiological changes of the cells caused by Ca-alginate immobilization may have contributed to increased reaction rates. Degradation rates for repeated operations increased for successive batches indicating that cells became better adapted to the reaction conditions over time.     

A microbial consortium isolated from a crude oil sample that uses asphaltenes as a carbon and energy source

A microbial consortium capable of mineralizing asphaltenes was obtained from the Maya crude oil. The enrichment system was built with a glass column reactor containing mineral medium supplied with asphaltenes as energy and carbon source. The consortium growth was evaluated in Casoy agar during 40 weeks. The steady-state phase of the enriched bacterial community was observed after 10 weeks when the culture reach 10(5) to 10(6) CFU ml(-1). The isolates belong to bacterial genus reported for degradation of other hydrocarbons and they were identified as Corynebacterium sp., Bacillus sp., Brevibacillus sp. and Staphylococcus sp. The bacterial consortium growth was evaluated by a viable counts during 14 days exposed to different aeration, temperature, salinity, and pH conditions. The ability of the consortium to mineralize asphaltenes was evaluated using the method of ISO 9439 in glass column reactors of 20 x 3.2 cm during 13 days. Temperatures of 55 degrees C and salinity of 1.8% were growth limiting. The respiration of the microbial consortium using asphaltenes as a sole carbon source (800 micromoles CO2 in 13 days) was significantly higher than those of the samples containing only the microbial consortium (200 micromoles CO2) or only asphaltenes (300 micromoles CO2). These results indicated the existence of asphaltenes-degradating microbes in the crude oil and confirmed that the consortium could mineralize asphaltenes in conditions of room temperature, salinity of 100 ppm, aeration of 1 l min(-1) and pH of 7.4.     

Biodegradation of chlorpyrifos by enterobacter strain B-14 and its use in bioremediation of contaminated soils

Six chlorpyrifos-degrading bacteria were isolated from an Australian soil and compared by biochemical and molecular methods. The isolates were indistinguishable, and one (strain B-14) was selected for further analysis. This strain showed greatest similarity to members of the order Enterobacteriales and was closest to members of the Enterobacter asburiae group. The ability of the strain to mineralize chlorpyrifos was investigated under different culture conditions, and the strain utilized chlorpyrifos as the sole source of carbon and phosphorus. Studies with ring or uniformly labeled [(14)C]chlorpyrifos in liquid culture demonstrated that the isolate hydrolyzed chlorpyrifos to diethylthiophospshate (DETP) and 3, 5, 6-trichloro-2-pyridinol, and utilized DETP for growth and energy. The isolate was found to possess mono- and diphosphatase activities along with a phosphotriesterase activity. Addition of other sources of carbon (glucose and succinate) resulted in slowing down of the initial rate of degradation of chlorpyrifos. The isolate degraded the DETP-containing organophosphates parathion, diazinon, coumaphos, and isazofos when provided as the sole source of carbon and phosphorus, but not fenamiphos, fonofos, ethoprop, and cadusafos, which have different side chains. Studies of the molecular basis of degradation suggested that the degrading ability could be polygenic and chromosome based. Further studies revealed that the strain possessed a novel phosphotriesterase enzyme system, as the gene coding for this enzyme had a different sequence from the widely studied organophosphate-degrading gene (opd). The addition of strain B-14 (10(6) cells g(-1)) to soil with a low indigenous population of chlorpyrifos-degrading bacteria treated with 35 mg of chlorpyrifos kg(-1) resulted in a higher degradation rate than was observed in noninoculated soils. These results highlight the potential of this bacterium to be used in the cleanup of contaminated pesticide waste in the environment.     

Isolation and Description of a Stable Carbazole-Degrading Microbial Consortium Consisting of <Emphasis Type="Italic">Chryseobacterium</Emphasis> sp. NCY and <Emphasis Type="Italic">Achromobacter</Emphasis> sp<Emphasis Type="Italic">.</Emphasis> NCW

A stable microbial consortium, separated from a refinery wastewater sample, was able to utilize carbazole as the sole source of carbon, nitrogen, and energy, and liberated ammonia from excess nitrogen. Two bacterial strains (NCY and NCW) were isolated from the microbial consortium using a nutrient agar plate. Based on the 16S rDNA sequence analysis, the two bacteria were identified as Chryseobacterium sp. NCY and Achromobacter sp. NCW, respectively. No intermediates of carbazole degradation were detected by high-performance liquid chromatography. The substrate specificity assay showed that the consortium could utilize compounds similar to carbazole, such as phenanthrene, naphthalene, and imidazole. Neither the pure strain NCY nor NCW could degrade carbazole after domestication for several times. It was suggested that the two bacteria formed a microbial consortium capable of metabolizing carbazole.     

Biodegradation of 1,4-dioxane by a <Emphasis Type="Italic">Flavobacterium</Emphasis>

A dioxane-degrading consortium was enriched from soil obtained from a contaminated groundwater plume. The enriched consortium did not use dioxane as the sole source of carbon and energy but co-metabolized dioxane in the presence of tetrahydrofuran (THF). THF and dioxane concentrations up to 1000 ppm were degraded by the enriched consortium in about 2 weeks with a longer lag phase observable at 1000 ppm. Three colonies from the enriched consortium were then obtained on agar plates containing basal salts and glucose as the carbon source. Only one of the three colonies was capable of dioxane degradation. Further enrichment of this colony in liquid media led to a pure culture that grew on glucose and co-metabolically degraded dioxane after THF degradation. The rate and extent of dioxane degradation of this isolate increased with increasing THF concentration. This isolate was subsequently identified as a Flavobacterium by 16S rDNA sequencing. Using polymerase chain reaction (PCR) and denaturing gradient gel electrophoresis (DGGE) analysis of microbial populations, Flavobacterium was determined to be the dominant species in the enriched consortium and was distinct from the two other colonies that did not degrade dioxane. This is the first report of a dioxane-degrading Flavobacterium which is phylogenetically distinct from any previously identified dioxane degrader.     

Enantioselective degradation of the herbicide mecoprop [2-(2-methyl-4-chlorophenoxy) propionic acid] by mixed and pure bacterial cultures

Abstract A consortium of three bacteria was isolated from top soil through their capacity to utilise the chlorinated, aromatic herbicide mecoprop as a single growth substrate. The consortium constituted a tight association of Alcaligenes denitrificans, Pseudomonas glycinea and Pseudomonas marginalis . The culture exclusively degraded the ( R )-(+)-isomer of the herbicide while the ( S )-(−)-enantiomer remained unaffected. The mecoprop-degrading community could also degrade 2,4-dichlorophenoxyacetic acid, 2-methyl-4-chlorophenoxyacetic acid and racemic 2-phenoxypropionic acid. Initially, no single member of the consortium was able to degrade mecoprop as a pure culture but after prolonged incubation, A. denitrificans was able to grow on the herbicide as the sole source of carbon and energy.     

Degradation kinetics of 4-amino naphthalene-1-sulfonic acid by a biofilm-forming bacterial consortium under carbon and nitrogen limitations

By decolorization of azo dyes, caused by reductive cleavage of the azo linkage, toxic or recalcitrant amines are generated. The present study deals with the effect of the inflowing medium composition (C:N ratio) on the kinetic behavior of a bacterial biofilm-forming consortium, able to use as carbon, nitrogen and sulfur source, the molecule of 4-aminonaphthalene-1-sulfonic acid (4ANS), which is one of the most recalcitrant byproducts generated by decolorization of azo dyes. All the experiments were carried out at room temperature in a lab-scale packed-bed biofilm reactor. Because environmental conditions affect the bioreactor performance, two mineral salts media containing 4ANS, with distinct C:N ratios; 0.68 (carbon as the limiting nutrient) and 8.57 (nitrogen as the limiting nutrient) were used to evaluate their effect on 4ANS biodegradation. By HPLC and COD measurements, the 4ANS removal rates and removal efficiencies were determined. The cultivable bacterial strains that compose the consortium were identified by their 16S rDNA gene sequence. With the enrichment technique used, a microbial consortium able to use efficiently 4ANS as the sole carbon source and energy, nitrogen and sulfur, was selected. The bacterial strains that constitute the consortium were isolated and identified. They belong to the following genera: Bacillus, Arthrobacter, Microbacterium, Nocardioides, and Oleomonas. The results obtained with this consortium showed, under nitrogen limitation, a remarkable increase in the 4ANS removal efficiency η(ANS), and in the 4ANS volumetric removal rates R (V,4ANS), as compared to those obtained under carbon limitation. Differences observed in bioreactor performance after changing the nutrient limitation could be caused by changes in biofilm properties and structure.     

Hydrocarbon degradation capacity and population dynamics of a microbial consortium obtained using a sequencing batch reactor in the presence of molasses

A native microbial consortium capable of degrading hydrocarbons was employed as an inoculum source in a sequencing batch reactor (SBR) using molasses as a carbon source. The microbial biomass in the SBR was able to grow in the presence of molasses, degrading 88% of the reducing sugar. Moreover, the consortium produced in the SBR was capable of maintaining 75% of the capacity for biodegradation of oil with respect to the original capacity of the native microbial consortium. Monitoring of the microbial population structure was accomplished using PCR-DGGE. The results indicated that the microbial populations grown in molasses were stable during crude oil degradation, as judged by comparison to the population structure of the native microbial consortium. The results obtained demonstrated that molasses could be used as a carbon source to promote the growth of biomass with oildegrading capacity.     

含有甲烷氧化菌的混合菌群特性研究

为获得高效甲烷氧化微生物体系,从农业土壤中采样,以甲烷作为唯一碳源进行好氧选择性传代培养,得到生长性能稳定、生长优于Methylosinus trichosporium OB3b纯培养的具有甲烷单加氧酶(Methane Monooxygenase,MMO)活性甲烷氧化混合菌。利用MMO的共代谢特性,分别以苯酚和环氧丙烷作为目标对象,考察该混合菌对有机污染物的降解及用于生产有用化学物质的催化特性。结果表明,所得混合菌具有高效降解苯酚能力,对初始浓度为600mg/L的苯酚,经过11h培养,苯酚降解率可达99%。另外,以该混合菌为催化剂可以实现丙烯氧化生产环氧丙烷。通过降低磷酸盐浓度可以有效提高环氧丙烷的积累浓度,最大可至5mmol/L。此外,采用纯种分离方法结合PCR扩增、16SrRNA和MMO功能基因分析技术对混合菌群结构进行解析。结果表明,该混合菌群由Ⅱ型甲烷氧化菌及其它至少4种非甲烷氧化菌组成,它们分别属于Methylosinus trichosporium和Acinetobacter junii、Cupriavidusme tallidurans、Comamonas testosteroni和Stenotrophomonas maltophilia。采用PCR方法从混合菌及纯化菌株M.trichosporiums Y9总DNA中都能扩增得到mmoB、mmoX和pmoA基因片段,表明该甲烷氧化菌同时具有sMMO和pMMO两种形式的MMO。通过对从甲烷氧化混合菌中分离纯化得到的甲烷氧化菌进行PCR产物测序,结果发现其与Methylosinus trichosporium的同源性为99.9%。     

Enhanced Biodegradation of Methyl tert-butyl-ether by a Microbial Consortium

The widespread use of Methyl tert-butyl-ether (MTBE) as a gasoline additive has resulted in a higher detection rate of MTBE in groundwater systems. Therefore, the researchers show more concern about the bioremediation of MTBE-impacted aquifers. In this paper, a MTBE-direct-degrading bacterial consortium was enriched (named RS1) and further studied. In order to identify the microbial community of the consortium, 17 and 12 different single strains were isolated from nutrient medium and MSM media (with MTBE as the sole carbon source), respectively. 16S rDNA-based phylogenetic analysis revealed that these diverse bacteria belonged to 14 genera, in which Pseudomonas was dominant. Several strains which can grow with MTBE as the sole carbon and energy source were also identified, such as M1, related to MTBE-degrading Arthrobacter sp. ATCC27778. Furthermore, the appropriate addition of certain single strain in consortium RS1 (M1:RS1 = 1:2) facilitates MTBE degradation by increasing the quantity of efficient MTBE-degrading bacteria. This work will provide microbial source and theoretical fundament for further bioremediation of MTBE-contaminated aquifers, which has applied potential and environmental importance.     

Biodegradation of Chlorpyrifos by Enterobacter Strain B-14 and Its Use in Bioremediation of Contaminated Soils

Six chlorpyrifos-degrading bacteria were isolated from an Australian soil and compared by biochemical and molecular methods. The isolates were indistinguishable, and one (strain B-14) was selected for further analysis. This strain showed greatest similarity to members of the order Enterobacteriales and was closest to members of the Enterobacter asburiae group. The ability of the strain to mineralize chlorpyrifos was investigated under different culture conditions, and the strain utilized chlorpyrifos as the sole source of carbon and phosphorus. Studies with ring or uniformly labeled [¹⁴C]chlorpyrifos in liquid culture demonstrated that the isolate hydrolyzed chlorpyrifos to diethylthiophospshate (DETP) and 3, 5, 6-trichloro-2-pyridinol, and utilized DETP for growth and energy. The isolate was found to possess mono- and diphosphatase activities along with a phosphotriesterase activity. Addition of other sources of carbon (glucose and succinate) resulted in slowing down of the initial rate of degradation of chlorpyrifos. The isolate degraded the DETP-containing organophosphates parathion, diazinon, coumaphos, and isazofos when provided as the sole source of carbon and phosphorus, but not fenamiphos, fonofos, ethoprop, and cadusafos, which have different side chains. Studies of the molecular basis of degradation suggested that the degrading ability could be polygenic and chromosome based. Further studies revealed that the strain possessed a novel phosphotriesterase enzyme system, as the gene coding for this enzyme had a different sequence from the widely studied organophosphate-degrading gene (opd). The addition of strain B-14 (10⁶ cells g⁻¹) to soil with a low indigenous population of chlorpyrifos-degrading bacteria treated with 35 mg of chlorpyrifos kg⁻¹ resulted in a higher degradation rate than was observed in noninoculated soils. These results highlight the potential of this bacterium to be used in the cleanup of contaminated pesticide waste in the environment.     

Isolation and initial characterization of a bacterial consortium able to mineralize fluorobenzene.

Fluorinated compounds are known to be more resistant to microbial degradation than other halogenated chemicals. A microbial consortium capable of aerobic biodegradation of fluorobenzene (FB) as the sole source of carbon and energy was isolated by selective enrichment from sediments collected in a drain near an industrial site. A combination of three microbial strains recovered from the enriched consortium was shown to be necessary for complete FB mineralization. Two of the strains (F1 and F3) were classified by 16S rRNA analysis as belonging to the Sphingobacterium/Flavobacterium group, while the third (F4) falls in the beta-Proteobacteria group, clustering with Alcaligenes species. Strain F4 was consistently found in the liquid cultures in a much greater proportion than strains F1 and F3 (86:8:6 for F4, F1, and F3, respectively). Stoichiometric release of fluoride ions was measured in batch and fed-batch cultures. In batch cultures, the consortium was able to use FB up to concentrations of 400 mg liter(-1) and was able to utilize a range of other organic compounds, including 4-fluorophenol and 4-fluorobenzoate. To our knowledge this is the first time biodegradation of FB as a sole carbon source has been reported.     

Enzymatic dehalogenation of pentachlorophenol by Pseudomonas fluorescens of the microbial community from tannery effluent

Four different bacterial isolates obtained from a stable bacterial consortium were capable of utilizing pentachlorophenol (PCP) as sole carbon and energy source. The consortium was developed by continuous enrichment in the chemostat. The degradation of PCP by bacterial strain was preceded through an oxidative route as indicated by accumulation of tetrachloro-rho-hydroquinone and dichlorohydroquinone as determined by high performance liquid chromatography (HPLC). Among the four isolates, Pseudomonas fluorescens exhibited maximum degradation capability and enzyme production. PCP-monooxygenase enzyme was extracted from culture extract and fractionated by DEAE-cellulose ion exchange chromatography. The molecular weight of the enzyme, purified from Pseudomonas fluorescens, determined by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) and gel filtration chromatography was found to be 24000 Da.     

Decolourisation of effluent from the textile industry by a microbial consortium

Summary A microbial consortium, PDW, was isolated capable of the rapid decolourisation of commercially important textile dyes under anaerobic conditions. Decolourisation was dependent upon the presence of a carbon and energy source in addition to the textile dyes. PDW was capable of dye decolourisation when utilising cheap and readily available carbon sources such lactose, starch and distillery waste. PDW removed 76% of colour from textile plant effluent after 3 days.     

A GAC biofilm reactor for the continuous degradation of 4-chlorophenol: treatment efficiency and microbial analysis

Using a continuous enrichment technique, a bacterial consortium capable of degrading 4-chlorophenol (4-CP) was obtained from the rhizosphere of Phragmites australis. A granular activated carbon (GAC) biofilm reactor was established using this consortium, and the degradation of 4-CP was investigated under continuous flow operation using a feed of 20-50 mg l(-1) with a hydraulic residence time of 17 min over a 6-month period. Chloride liberation occurred throughout the operation, and the reactor had 4-CP removal efficiencies of 69-100%. Periods of lower performance were attributed to clogging of the column with biomass and the formation of channels. Subsequently, the immobilized biofilm was subjected to a starvation period of 5 months, after which its degradative capacity was still maintained. The microbial consortium was characterized during the continuous flow experiment and dynamic population changes were observed throughout. One isolate recovered from the biofilm was shown to be capable of degrading 4-CP as a sole carbon and energy source.     

First evidence of mineralization of petroleum asphaltenes by a strain of Neosartorya fischeri

A fungal strain isolated from a microbial consortium growing in a natural asphalt lake is able to grow in purified asphaltenes as the only source of carbon and energy. The asphaltenes were rigorously purified in order to avoid contamination from other petroleum fractions. In addition, most of petroporphyrins were removed. The 18S rRNA and β‐tubulin genomic sequences, as well as some morphologic characteristics, indicate that the isolate is Neosartorya fischeri. After 11 weeks of growth, the fungus is able to metabolize 15.5% of the asphaltenic carbon, including 13.2% transformed to CO₂. In a medium containing asphaltenes as the sole source of carbon and energy, the fungal isolate produces extracellular laccase activity, which is not detected when the fungus grow in a rich medium. The results obtained in this work clearly demonstrate that there are microorganisms able to metabolize and mineralize asphaltenes, which is considered the most recalcitrant petroleum fraction.     

Architecture and spatial organization in a triple-species bacterial biofilm synergistically degrading the phenylurea herbicide linuron

Members of a triple-species 3-(3,4-dichlorophenyl)-1-methoxy-1-methyl urea (linuron)-mineralizing consortium, i.e. the linuron- and 3,4-dichloroaniline-degrading Variovorax sp. WDL1, the 3,4-dichloroaniline-degrading Comamonas testosteroni WDL7 and the N,O-dimethylhydroxylamine-degrading Hyphomicrobium sulfonivorans WDL6, were cultivated as mono- or multi-species biofilms in flow cells irrigated with selective or nonselective media, and examined with confocal laser scanning microscopy. In contrast to mono-species biofilms of Variovorax sp. WDL1, the triple-species consortium biofilm degraded linuron completely through apparent synergistic interactions. The triple-species linuron-fed consortium biofilm displayed a heterogeneous structure with an irregular surface topography that most resembled the topography of linuron-fed mono-species WDL1 biofilms, indicating that WDL1 had a dominating influence on the triple-species biofilm architecture. This architecture was dependent on the carbon source supplied, as the biofilm architecture of WDL1 growing on alternative carbon sources was different from that observed under linuron-fed conditions. Linuron-fed triple-species consortium biofilms consisted of mounds composed of closely associated WDL1, WDL7 and WDL6 cells, while this association was lost when the consortium was grown on a nonselective carbon source. In addition, under linuron-fed conditions, microcolonies displaying associated growth developed rapidly after inoculation. These observations indicate that the spatial organization in the linuron-fed consortium biofilm reflected the metabolic interactions within the consortium.     

A lava rock-based biofilter for the treatment of alpha-pinene

Biofiltration is an emerging technology in the United States that utilizes microorganisms to biodegrade harmful contaminants in air to carbon dioxide and water. Biofiltration is not only more cost effective, but also more environmentally friendly than traditional technologies such as thermal oxidation and chemical scrubbing. The primary objectives of the study were to operate a lava rock-based laboratory biofiltration system for the removal of alpha-pinene. A consortium of microorganisms to be used as an inoculum was recovered that was able to use alpha-pinene as a sole source of carbon and energy. The removal of alpha-pinene from the laboratory system was monitored with a total hydrocarbon analyzer (THA). Based on THA analysis, elimination capacities as high as 100+g/m(3)/h were obtained in the laboratory biofilters. Removal efficiencies averaged 99% over a two year period. The solid support maintained a neutral pH with no buffer addition throughout the two year study and microbial levels were maintained between 10(6) and 10(7) colony forming units (CFU)/g of solid support. Bacillus and Rhodococcus species were found to be the majority of the microorganisms in the biofilters over a two year period. This is the first time an organism from either of these genera has been reported to utilize alpha-pinene as a sole source of carbon and energy. Overall, a preselected consortium of microorganisms coupled with lava rock as a biofilter solid support achieved extended alpha-pinene treatment levels that far exceed previously published values.     

Aerobic biodegradation of 4-methylquinoline by a soil bacterium.

Methylquinolines and related N-heterocyclic aromatic compounds are common contaminants associated with the use of hydrocarbons in both coal gasification and wood treatment processes. These compounds have been found in groundwater, and many are known mutagens. A stable, five-member bacterial consortium able to degrade 4-methylquinoline was established by selective enrichment using soil collected from an abandoned coal gasification site. The consortium was maintained for 5 years by serial transfer in a medium containing 4-methylquinoline. A gram-negative soil bacterium, strain Lep1, was isolated from the consortium and shown to utilize 4-methylquinoline as a source of carbon and energy during growth in liquid medium. A time course experiment demonstrated that both the isolate Lep1 and the consortium containing Lep1 were able to degrade 4-methylquinoline under aerobic conditions. Complete degradation of 4-methylquinoline by either strain Lep1 alone or the consortium was characterized by the production and eventual disappearance of 2-hydroxy-4-methylquinoline, followed by the appearance and persistence of a second metabolite tentatively identified as a hydroxy-4-methylcoumarin. Currently, there is no indication that 4-methylquinoline degradation proceeds differently in the consortium culture compared with Lep1 alone. This is the first report of 4-methylquinoline biodegradation under aerobic conditions.