Showing papers in "Biodegradation in 2008"
TL;DR: This review has tried to cover the latest developments on enzyme systems of WRF, their low molecular mass mediators and their potential use for bioremediation of industrial pollutants.
Abstract: Increasing discharge and improper management of liquid and solid industrial wastes have created a great concern among industrialists and the scientific community over their economic treatment and safe disposal. White rot fungi (WRF) are versatile and robust organisms having enormous potential for oxidative bioremediation of a variety of toxic chemical pollutants due to high tolerance to toxic substances in the environment. WRF are capable of mineralizing a wide variety of toxic xenobiotics due to non-specific nature of their extracellular lignin mineralizing enzymes (LMEs). In recent years, a lot of work has been done on the development and optimization of bioremediation processes using WRF, with emphasis on the study of their enzyme systems involved in biodegradation of industrial pollutants. Many new strains have been identified and their LMEs isolated, purified and characterized. In this review, we have tried to cover the latest developments on enzyme systems of WRF, their low molecular mass mediators and their potential use for bioremediation of industrial pollutants.
446 citations
TL;DR: Partial nitrification to nitrite (nitritation) can be achieved in a continuous process without sludge retention by wash out of nitrite oxidisingacteria (NOB) while retaining ammonia oxidising bacteria (AOB) at elevated temperatures and at low dissolved oxygen (DO) concentrations.
Abstract: Partial nitrification to nitrite (nitritation) can be achieved in a continuous process without sludge retention by wash out of nitrite oxidising bacteria (NOB) while retaining ammonia oxidising bacteria (AOB), at elevated temperatures (the SHARON process) and, as demonstrated in this paper, also at low dissolved oxygen (DO) concentrations. Enriched AOB was attained at a low DO concentration (0.4 mg l(-1)) and a dilution rate of 0.42 day(-1) in a continuous process. A higher oxygen affinity of AOB compared to NOB seemed critical to achieving this. This was verified by determining the oxygen half saturation constant, Ko, with similar oxygen mass transfer resistances for enriched AOB and NOB as 0.033+/-0.003 mg l(-1) and 0.43+/-0.08 mg l(-1), respectively. However, the extent of nitritation attained was found to be highly sensitive to process upsets.
355 citations
TL;DR: This study demonstrates the high affinity of C208 to polystyrene which lead to biofilm formation and, presumably, induced partial biodegradation.
Abstract: Polystyrene, which is one of the most utilized thermoplastics, is highly durable and is considered to be non-biodegradable. Hence, polystyrene waste accumulates in the environment posing an increasing ecological threat. In a previous study we have isolated a biofilm-producing strain (C208) of the actinomycete Rhodococcus ruber that degraded polyethylene films. Formation of biofilm, by C208, improved the biodegradation of polyethylene. Consequently, the present study aimed at monitoring the kinetics of biofilm formation by C208 on polystyrene, determining the physiological activity of the biofilm and analyzing its capacity to degrade polystyrene. Quantification of the biofilm biomass was performed using a modified crystal violet (CV) staining or by monitoring the protein content in the biofilm. When cultured on polystyrene flakes, most of the bacterial cells adhered to the polystyrene surface within few hours, forming a biofilm. The growth of the on polystyrene showed a pattern similar to that of a planktonic culture. Furthermore, the respiration rate, of the biofilm, exhibited a pattern similar to that of the biofilm growth. In contrast, the respiration activity of the planktonic population showed a constant decline with time. Addition of mineral oil (0.005% w/v), but not non-ionic surfactants, increased the biofilm biomass. Extended incubation of the biofilm for up to 8 weeks resulted in a small reduction in the polystyrene weight (0.8% of gravimetric weight loss). This study demonstrates the high affinity of C208 to polystyrene which lead to biofilm formation and, presumably, induced partial biodegradation.
203 citations
TL;DR: A bacterium capable of utilizing pyrethroid pesticide cypermethrin as sole source of carbon was isolated from soil and identified as a Micrococcus sp.
Abstract: A bacterium capable of utilizing pyrethroid pesticide cypermethrin as sole source of carbon was isolated from soil and identified as a Micrococcus sp. The organism also utilized fenvalerate, deltamethrin, perimethrin, 3-phenoxybenzoate, phenol, protocatechuate and catechol as growth substrates. The organism degraded cypermethrin by hydrolysis of ester linkage to yield 3-phenoxybenzoate, leading to loss of its insecticidal activity. 3-Phenoxybenzoate was further metabolized by diphenyl ether cleavage to yield protocatechuate and phenol as evidenced by isolation and identification of metabolites and enzyme activities in the cell-free extracts. Protocatechuate and phenol were oxidized by ortho-cleavage pathway. Thus, the organism was versatile in detoxification and complete mineralization of pyrethroid cypermethrin
176 citations
TL;DR: In this paper, the authors used thermal analysis and Fourier transform infrared spectroscopy (FTIR) techniques to characterize the stability of compost extracts and found that the degradation of easily oxidizable organic matter was more intense for non-aerated processes than for aerated extractions.
Abstract: Compost extract or “compost tea” is a liquid extract of compost obtained by mixing compost and water for a defined period of time. Compost tea contains nutrients and a range of different organisms and is applied to the soil or directly to plants with the principal aim of suppressing certain plant diseases. In addition, the application of compost tea supplies nutrients and organic matter to the soil. Thermal analysis and Fourier transform infrared spectroscopy (FTIR) are two widely applied analytical techniques for establishing the stability of compost, and although numerous studies have evaluated the capacity of compost tea to suppress plant diseases, there are no studies employing these techniques to characterize compost-tea. For the present study, 12 compost extracts were produced under varying conditions in a purpose-built reactor. Two different composts, an stable compost produced from manure and an unstable compost produced from municipal solid waste, respectively, two aeration systems (aerated and non-aerated extracts) and three temperatures (10, 20 and 30°C) were used in these experiments. The extracts were freeze-dried and subsequently analysed, together with the two composts, by means of FTIR and thermal analysis. Extracts produced from high stability compost, independently of the conditions of aeration and temperature, showed very similar results. In contrast, differences among extracts produced from the unstable compost were more noticeable. However, the different conditions of aeration and temperature during the production of the extracts only explained partially these differences, since the transformations undergone by compost over the 3 months that the experiments lasted were also reflected in the composition of the extracts. In spite of everything, extraction process favoured the degradation of easily oxidizable organic matter, which was more abundant in unstable compost. This degradation was more intense for non-aerated processes, probably due to the longer duration of these (10 days) with respect to aerated extractions (2 days). The effect of temperature was not clear in these experiments, although high temperatures could increase micro organism activity and consequently favour the degradation of easily oxidizable organic matter.
119 citations
TL;DR: Chlorinated benzenes are important industrial intermediates and solvents, and mono-chlorinated benzene is recalcitrant to biotransformation under anaerobic conditions.
Abstract: Chlorinated benzenes are important industrial intermediates and solvents. Their widespread use has resulted in broad distribution of these compounds in the environment. Chlorobenzenes (CBs) are subject to both aerobic and anaerobic metabolism. Under aerobic conditions, CBs with four or less chlorine groups are susceptible to oxidation by aerobic bacteria, including bacteria (Burkholderia, Pseudomonas, etc.) that grow on such compounds as the sole source of carbon and energy. Sound evidence for the mineralization of CBs has been provided based on stoichiometric release of chloride or mineralization of 14C-labeled CBs to 14CO2. The degradative attack of CBs by these strains is initiated with dioxygenases eventually yielding chlorocatechols as intermediates in a pathway leading to CO2 and chloride. Higher CBs are readily reductively dehalogenated to lower chlorinated benzenes in anaerobic environments. Halorespiring bacteria from the genus Dehalococcoides are implicated in this conversion. Lower chlorinated benzenes are less readily converted, and mono-chlorinated benzene is recalcitrant to biotransformation under anaerobic conditions.
116 citations
TL;DR: A pathway in which HMW PAHs are degraded into the β-ketoadipate pathway through protocatechuate and then mineralized to CO2 via TCA cycle is proposed and identified 67 and 23 genes involved in PAH degradation and T CA cycle pathways, respectively, to be expressed as proteins.
Abstract: Mycobacterium vanbaalenii PYR-1 is well known for its ability to degrade a wide range of high-molecular-weight (HMW) polycyclic aromatic hydrocarbons (PAHs). The genome of this bacterium has recently been sequenced, allowing us to gain insights into the molecular basis for the degradation of PAHs. The 6.5 Mb genome of PYR-1 contains 194 chromosomally encoded genes likely associated with degradation of aromatic compounds. The most distinctive feature of the genome is the presence of a 150 kb major catabolic region at positions 494 approximately 643 kb (region A), with an additional 31 kb region at positions 4,711 approximately 4,741 kb (region B), which is predicted to encode most enzymes for the degradation of PAHs. Region A has an atypical mosaic structure made of several gene clusters in which the genes for PAH degradation are complexly arranged and scattered around the clusters. Significant differences in the gene structure and organization as compared to other well-known aromatic hydrocarbon degraders including Pseudomonas and Burkholderia were revealed. Many identified genes were enriched with multiple paralogs showing a remarkable range of diversity, which could contribute to the wide variety of PAHs degraded by M. vanbaalenii PYR-1. The PYR-1 genome also revealed the presence of 28 genes involved in the TCA cycle. Based on the results, we proposed a pathway in which HMW PAHs are degraded into the beta-ketoadipate pathway through protocatechuate and then mineralized to CO2 via TCA cycle. We also identified 67 and 23 genes involved in PAH degradation and TCA cycle pathways, respectively, to be expressed as proteins.
115 citations
TL;DR: This is the first study describing that bacteria able to metabolize E2, can subsequently cometabolize EE2 at low μg/l levels, suggesting that total degradation and cleavage of the aromatic ring occurred.
Abstract: 17α-ethinylestradiol (EE2), the active compound of the contraceptive pill, is a recalcitrant estrogen, which is encountered at ng/l levels in wastewater treatment plant (WWTP) effluents and rivers and can cause feminization of aquatic organisms. The aim of this study was to isolate micro-organisms that could remove such low EE2 concentrations. In this study, six bacterial strains were isolated from compost that cometabolize EE2 when metabolizing estrone (E1), 17β-estradiol (E2) and estriol (E3). The strains belong to the α, β and γ-Proteobacteria. All six strains metabolize E2 over E1, at μg/l to ng/l concentrations. In 4 days, initial concentrations of 0.5 μg E2/l and 0.6 μg EE2/l were degraded to 1.8 ± 0.4 ng E2/l and 85 ± 16 ng EE2/l, respectively. No other metabolites besides E1, E2, E3 or EE2 were detected, suggesting that total degradation and cleavage of the aromatic ring occurred. This is the first study describing that bacteria able to metabolize E2, can subsequently cometabolize EE2 at low μg/l levels.
105 citations
TL;DR: Halomonas sp strain GTW was newly isolated from coastal sediments contaminated by chemical wastewater and was identified to be a member of the genus Halomonas by 16S rDNA sequence analysis and physical and biochemical tests, and demonstrated that the bacteria could decolorize different azo dyes under high salt concentration conditions.
Abstract: Halomonas sp strain GTW was newly isolated from coastal sediments contaminated by chemical wastewater and was identified to be a member of the genus Halomonas by 16S rDNA sequence analysis and physical and biochemical tests. The optimal decolorization conditions were as follows: temperature 30°C, pH 6.5.0–8.5, NaCl 10–20% (w/v) and the optimal carbon source was yeast exact. The results of experiments demonstrated that the bacteria could decolorize different azo dyes under high salt concentration conditions, and the decolorization rate of five tested azo dyes could be above 90% in 24 h. The exploitation of the salt-tolerant bacteria in the bio-treatment system would be a great improvement of conventional biological treatment systems and the bio-treatment concept.
104 citations
TL;DR: It is suggested that fungal remediation is promising in eliminating PAHs, especially the part of recalcitrant and highly toxic benzo[a]pyrene, in contaminated soil.
Abstract: Microcosms were set up with a PAHs-contaminated soil using biostimulation (addition of ground corn cob) and bioaugmentation (inoculated with Monilinia sp. W5-2). Degradation of polycyclic aromatic hydrocarbons and microbial community were examined at the end of incubation period. After 30 days, bioaugmented microcosms showed a 35 ± 0% decrease in total PAHs, while biostimulated and control microcosms showed 16 ± 9% and 3 ± 0% decrease in total PAHs, respectively. Bioaugmented microcosms also revealed 70 ± 8% and 72 ± 2% decreases in benzo[a]pyrene and anthracene, respectively, while the values for biostimulated and control microcosms were much lower. Detoxification of soils in bioaugmented microcosms was confirmed by genetic toxicity assay, suggesting important role of fungal remediation. Molecular fingerprint profiles and selective enumeration showed biostimulation with ground corn cob increased both number and abundance of indigenous aromatic hydrocarbons degraders and changed microbial community composition in soil, which is beneficial to natural attenuation of PAHs. At the same time, bioaugmentation with Monilinia strain W5-2 imposed negligible effect on indigenous microbial community. This study suggests that fungal remediation is promising in eliminating PAHs, especially the part of recalcitrant and highly toxic benzo[a]pyrene, in contaminated soil. It is also the first description of soil bioremediation with Monilinia sp.
99 citations
TL;DR: The generated model appropriately predicted the biodegradation kinetics in mixtures using parameter estimates from the sole substrate experiments, validating the hypothesis of a common rate-determining step and demonstrating the effect that interactions can have on individual chemical kinetics.
Abstract: Many contaminated sites commonly have complex mixtures of polycyclic aromatic hydrocarbons (PAHs) whose individual microbial biodegradation may be altered in mixtures. Biodegradation kinetics for fluorene, naphthalene, 1,5-dimethylnaphthalene and 1-methylfluorene were evaluated in sole substrate, binary and ternary systems using Sphingomonas paucimobilis EPA505. The first order rate constants for fluorene, naphthalene, 1,5-dimethylnaphthalene, and 1-methylfluorene were comparable; yet Monod parameters were significantly different for the tested PAHs. S. paucimobilis completely degraded all the components in binary and ternary mixtures; however, the initial degradation rates of individual components decreased in the presence of competitive PAHs. Results from the mixture experiments indicate competitive interactions, demonstrated mathematically. The generated model appropriately predicted the biodegradation kinetics in mixtures using parameter estimates from the sole substrate experiments, validating the hypothesis of a common rate-determining step. Biodegradation kinetics in mixtures were affected by the affinity coefficients of the co-occurring PAHs and mixture composition. Experiments with equal concentrations of substrates demonstrated the effect of concentration on competitive inhibition. Ternary experiments with naphthalene, 1,5-dimethylnaphthalene and 1-methylfluorene revealed delayed degradation, where depletion of naphthalene and 1,5-dimethylnapthalene occurred rapidly only after the complete removal of 1-methylfluorene. The substrate interactions observed in mixtures require a multisubstrate model to account for simultaneous degradation of substrates. PAH contaminated sites are far more complex than even ternary mixtures; however these studies clearly demonstrate the effect that interactions can have on individual chemical kinetics. Consequently, predicting natural or enhanced degradation of PAHs cannot be based on single compound kinetics as this assumption would likely overestimate the rate of disappearance.
TL;DR: Demethoxylation reactions in the cultures of the brown-rot fungi Gloeophyllum trabeum and Poria placenta were studied by determining the evolution of 14CO2 from a non-phenolic lignin model, β–O–4 dimer, and from [O14CH3]-labelled vanillic acid (model II).
Abstract: Demethoxylation reactions in the cultures of the brown-rot fungi Gloeophyllum trabeum and Poria placenta were studied by determining the evolution of 14CO2 from a non-phenolic lignin model, β–O–4 dimer, [O14CH3]-labelled at position 4 in the A ring (model I), and from [O14CH3]-labelled vanillic acid (model II). The fungi were grown under oxygen or air atmosphere on an agar medium with or without spruce sapwood blocks. The dimeric model (I) was impregnated onto agar or wood block in cultures to clarify the possible effect of wood as growth substrate. In the case of vanillic acid (model II), birch wood was used. The effect of supplemented nutrient nitrogen (2 mM N) and glucose (0.1 or 1.0% w/v) on demethoxylation was also studied. G. trabeum enhanced the production of 14CO2 from the dimer in the presence of spruce wood blocks. It released 14CO2 from the methoxyl groups giving 30–60% of the applied activity in 8 weeks. P. placenta produced almost 30% 14CO2 from vanillic acid (model II) in 9 weeks under oxygen, but from the methoxyl group of the dimer only 3% of 14CO2 was evolved in 4 weeks. The biomasses determined as ergosterol assay showed variation from 14 to 226 μg g−1 dry weight of agar, and 2 to 9 μg g−1 of wood, but they did not correlate with the production of 14CO2. The results indicate that these brown-rot fungi possess different mechanisms for demethoxylation.
TL;DR: Results indicate that on-site aerobic bioremediation of HCH exploiting the biodegradation activity of S. indicum B90A cells stored on corncob powder is a promising technology.
Abstract: Soil pollution with hexachlorocyclohexane (HCH) has caused serious environmental problems. Here we describe the targeted degradation of all HCH isomers by applying the aerobic bacterium Sphingobium indicum B90A. In particular, we examined possibilities for large-scale cultivation of strain B90A, tested immobilization, storage and inoculation procedures, and determined the survival and HCH-degradation activity of inoculated cells in soil. Optimal growth of strain B90A was achieved in glucose-containing mineral medium and up to 65% culturability could be maintained after 60 days storage at 30°C by mixing cells with sterile dry corncob powder. B90A biomass produced in water supplemented with sugarcane molasses and immobilized on corncob powder retained 15–20% culturability after 30 days storage at 30°C, whereas full culturability was maintained when cells were stored frozen at −20°C. On the contrary, cells stored on corncob degraded γ-HCH faster than those that had been stored frozen, with between 15 and 85% of γ-HCH disappearance in microcosms within 20 h at 30°C. Soil microcosm tests at 25°C confirmed complete mineralization of [14C]-γ-HCH by corncob-immobilized strain B90A. Experiments conducted in small pits and at an HCH-contaminated agricultural site resulted in between 85 and 95% HCH degradation by strain B90A applied via corncob, depending on the type of HCH isomer and even at residual HCH concentrations. Up to 20% of the inoculated B90A cells survived under field conditions after 8 days and could be traced among other soil microorganisms by a combination of natural antibiotic resistance properties, unique pigmentation and PCR amplification of the linA genes. Neither the addition of corncob nor of corncob immobilized B90A did measurably change the microbial community structure as determined by T-RFLP analysis. Overall, these results indicate that on-site aerobic bioremediation of HCH exploiting the biodegradation activity of S. indicum B90A cells stored on corncob powder is a promising technology.
TL;DR: A phylogenetic tree of the isolates constructed using their 16S rDNA sequences revealed that the isolate were divided into six genera plus one family (Acinetobacter, Rhodococcus, Gordonia, Pseudomonas, Ralstonia, Bacillus and Alcaligenaceae, respectively).
Abstract: Thirty-six bacteria that degraded long-chain hydrocarbons were isolated from natural environments using long-chain hydrocarbons (waste car engine oil, base oil or the c-alkane fraction of base oil) as the sole carbon and energy source. A phylogenetic tree of the isolates constructed using their 16S rDNA sequences revealed that the isolates were divided into six genera plus one family (Acinetobacter, Rhodococcus, Gordonia, Pseudomonas, Ralstonia, Bacillus and Alcaligenaceae, respectively). Furthermore, most of the isolates (27 of 36) were classified into the genera Acinetobacter, Rhodococcus or Gordonia. The hydrocarbon-degradation similarity in each strain was confirmed by the 2,6-dichlorophenol indophenol (2,6-DCPIP) assay. Isolates belonging to the genus Acinetobacter degraded long-chain normal alkanes (n-alkanes) but did not degrade short-chain n-alkanes or cyclic alkanes (c-alkanes), while isolates belonging to the genera Rhodococcus and Gordonia degraded both long-chain n-alkanes and c-alkanes.
TL;DR: Experiment designed to track the metabolic pathway showed that pyridine ring was cleaved between the C2 and N, then the mineralization of the carbonous intermediate products may comply with the early proposed pathway and the transformation of the nitrogen may proceed on a new pathway of simultaneous heterotrophic nitrification and aerobic denitrification.
Abstract: A bacterial strain using pyridine as sole carbon, nitrogen and energy source was isolated from the activated sludge of a coking wastewater treatment plant. By means of morphologic observation, physiological characteristics study and 16S rRNA gene sequence analysis, the strain was identified as the species of Paracoccus. The strain could degrade 2,614 mg l−1 of pyridine completely within 49.5 h. Experiment designed to track the metabolic pathway showed that pyridine ring was cleaved between the C2 and N, then the mineralization of the carbonous intermediate products may comply with the early proposed pathway and the transformation of the nitrogen may proceed on a new pathway of simultaneous heterotrophic nitrification and aerobic denitrification. During the degradation, NH3-N occurred and increased along with the decrease of pyridine in the solution; but the total nitrogen decreased steadily and equaled to the quantity of NH3-N when pyridine was degraded completely. Adding glucose into the medium as the extra carbon source would expedite the biodegradation of pyridine and the transformation of the nitrogen. The fragments of nirS gene and nosZ gene were amplified which implied that the BW001 had the potential abilities to reduce NO2− to NO and/or N2O, and then to N2.
TL;DR: This study investigated extracellular electron shuttle-mediated RDX biodegradation and the distribution of ring cleavage metabolites generated by biological degradation versus the products formed by abiotic degradation (reduced electron shuttles), and when the two pathways were acting simultaneously.
Abstract: This study investigated extracellular electron shuttle-mediated RDX biodegradation and the distribution of ring cleavage metabolites generated by biological degradation (cells) versus the products formed by abiotic degradation (reduced electron shuttles), and when the two pathways were acting simultaneously. All pathways were influenced by pH. Buffered suspensions (pH 6.8/7.9/9.2) were performed with cell-free anthrahydroquinone-2,6-disulfonate as the sole electron donor, cells (Geobacter metallireducens) + acetate, or cells/acetate + anthraquinone-2,6-disulfonate as an electron shuttle. The metabolites identified included methylenedinitramine, formaldehyde, nitrous oxide, nitrite, ammonium and carbon dioxide. As pH increased, the rates of RDX reduction by AH2QDS also increased. Cells alone reduced RDX faster at the lower pH values. However, at all pH the rates of the electron shuttle-mediated pathways were consistently the fastest, and the proportion of carbon present as formaldehyde, which is a precursor to mineralization, was highest in the presence of electron shuttles. Formaldehyde accounted for 45/51/54% of the carbon in electron shuttle amended cell suspensions as opposed to 13/42/45% of carbon without shuttles at the pH 6.8/7.9/9.2, respectively. Approximately 7–20% of RDX was mineralized to CO2 in the presence of cells at all pH tested; AQDS increased the extent of 14CO2 produced. Nitrous oxide and nitrite were end products in the strictly abiotic pathway, but nitrite was depleted in the presence of cells to form ammonium. Understanding the different products formed in the abiotic versus biological pathways and the influence of pH is critical to developing mixed biotic–abiotic remediation strategies for RDX.
TL;DR: The kinetics of degradation of the substituted phenols suggest that the preferential order of their depletion could be due to their respective pKa values and that the dissociated phenolate ions are the substrates.
Abstract: In this study the chlorophenol-degrading actinobacterium, Arthrobacter chlorophenolicus A6, was tested for its ability to grow on mixtures of phenolic compounds. During the experiments depletion of the compounds was monitored, as were cell growth and activity. Activity assays were based on bioluminescence output from a luciferase-tagged strain. When the cells were grown on a mixture of 4-chlorophenol, 4-nitrophenol and phenol, 4-chlorophenol degradation apparently was delayed until 4-nitrophenol was almost completely depleted. Phenol was degraded more slowly than the other compounds and not until 4-nitrophenol and 4-chlorophenol were depleted, despite this being the least toxic compound of the three. A similar order of degradation was observed in non-sterile soil slurries inoculated with A. chlorophenolicus. The kinetics of degradation of the substituted phenols suggest that the preferential order of their depletion could be due to their respective pKa values and that the dissociated phenolate ions are the substrates. A mutant strain (T99), with a disrupted hydroxyquinol dioxygenase gene in the previously described 4-chlorophenol degradation gene cluster, was also studied for its ability to grow on the different phenols. The mutant strain was able to grow on phenol, but not on either of the substituted phenols, suggesting a different catabolic pathway for the degradation of phenol by this microorganism.
TL;DR: It is suggested that effective RDX bioremediation by strain YH1 requires the design of a treatment scheme that includes initial removal of ammonium, nitrite, nitrate and TNT before RDX degradation can take place.
Abstract: We hypothesized that biodegradation of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX)--a widely used explosive contaminating soil and groundwater--by Rhodococcus strain YH1 is controlled by the presence of external nitrogen sources This strain is capable of degrading RDX while using it as sole nitrogen source under aerobic conditions Both inorganic and organic nitrogen sources were found to have a profound impact on RDX-biodegradation activity This effect was tested in growing and resting cells of strain YH1 Nitrate and nitrite delayed the onset of RDX degradation by strain YH1, while ammonium inhibited it almost completely In addition, 2,4,6-trinitrotoluene (TNT) inhibited RDX degradation and growth of strain YH1 On the other hand, tetrahydrophthalamide did not influence biodegradation or growth Growth on RDX induced the expression of a cytochrome P-450 enzyme that is suggested to be involved in the first step in the aerobic pathway of RDX degradation, as identified by SDS-PAGE analysis Ammonium and nitrite strongly repressed cytochrome P-450 expression Our findings suggest that effective RDX bioremediation by strain YH1 requires the design of a treatment scheme that includes initial removal of ammonium, nitrite, nitrate and TNT before RDX degradation can take place
TL;DR: A versatile bacterial strain able to convert polycyclic aromatic hydrocarbons (PAHs) was isolated, and a conversion by the isolate of both individual substances and PAH mixtures was investigated.
Abstract: A versatile bacterial strain able to convert polycyclic aromatic hydrocarbons (PAHs) was isolated, and a conversion by the isolate of both individual substances and PAH mixtures was investigated. The strain belonged to the Sphingomonas genus as determined on the basis of 16S rRNA analysis and was designated as VKM B-2434. The strain used naphthalene, acenaphthene, phenanthrene, anthracene and fluoranthene as a sole source of carbon and energy, and cometabolically oxidized fluorene, pyrene, benz[a]anthracene, chrysene and benzo[a]pyrene. Acenaphthene and fluoranthene were degraded by the strain via naphthalene-1,8-dicarboxylic acid and 3-hydroxyphthalic acid. Conversion of most other PAHs was confined to the cleavage of only one aromatic ring. The major oxidation products of naphthalene, phenanthrene, anthracene, chrysene, and benzo[a]pyrene were identified as salicylic acid, 1-hydroxy-2-naphthoic acid, 3-hydroxy-2-naphthoic acid, o-hydroxyphenanthroic acid and o-hydroxypyrenoic acid, respectively. Fluorene and pyrene were oxidized mainly to hydroxyfluorenone and dihydroxydihydropyrene, respectively. Oxidation of phenanthrene and anthracene to the corresponding hydroxynaphthoic acids occurred quantitatively. The strain converted phenanthrene, anthracene, fluoranthene and carbazole of coal-tar-pitch extract.
TL;DR: The LC-MS and NMR analysis confirms the oxidation of Indigo carmine and the primary degradation products were found to be Isatin sulfonic acid and anthranilicacid.
Abstract: The potential of recently isolated bacteria Paenibacillus larvae for the effective decolorization of Indigo carmine was evaluated. The effects of operational parameters (temperature, pH, dye concentration, shaking/non shaking) were tested. Maximum extent of decolorization was observed when the medium was incorporated with 10 g/l of yeast extract and peptone. Decolorization was strongly inhibited at non-shaken conditions as well as incorporation of inorganic sources (sodium nitrite and ammonium chloride) in the medium. Maximum decolorization was observed at 30°C (100%) and 40°C (92%) at 8 h of incubation. The LC-MS and NMR analysis confirms the oxidation of Indigo carmine .The primary degradation products were found to be Isatin sulfonic acid and anthranilicacid.
TL;DR: Both demethylation and degradation of AAP contribute to the weak bioefficacy of AAP in soil application and are probably originated from the structural differences of these insecticides.
Abstract: Our previous study found that Stenotrophomonas maltophilia CGMCC 1.1788 could hydroxylate imidacloprid (IMI) to 5-hydroxy IMI. Here we first report that S. maltophilia CGMCC 1.1788 can demethylate acetamiprid (AAP) to form IM 2-1 that was characterized by HPLC-MS/MS and NMR. IM 2-1 retained only 10.5% contact activity and 13.1% oral activity of AAP against horsebean aphid. Time course of biotransformation under existing of sucrose revealed that 58.9% of AAP disappeared, but only 16.7% of reduced AAP was transformed to IM 2-1, after 8 days. Both demethylation and degradation of AAP contribute to the weak bioefficacy of AAP in soil application. The differences in metabolism and detoxification pathways between AAP and IMI are probably originated from the structural differences of these insecticides.
TL;DR: Pseudomonasfluorescens-CS2 cells efficiently degraded ethylbenzene with enhanced efficiency compared to free cell cultures in single and two-phase systems, demonstrating that alginate and polyacrylamide matrices are more promising as compared to agar for cell immobilization.
Abstract: Pseudomonasfluorescens-CS2 metabolized ethylbenzene as the sole source of carbon and energy. The involvement of catechol as the hydroxylated intermediate during the biodegradation of ethylbenzene was established by TLC, HPLC and enzyme analysis. The specific activity of Catechol 2,3-dioxygenase in the cell free extracts of P.fluorescens-CS2 was determined to be 0.428 μmoles min−1 mg−1 protein. An aqueous-organic, Two-Phase Batch Culture System (TPBCS) was developed to overcome inhibition due to higher substrate concentrations. In TPBCS, P. fluorescens-CS2 demonstrated ethylbenzene utilization up to 50 mM without substrate inhibition on inclusion of n-decanol as the second phase. The rate of ethylbenzene metabolism in TPBCS was found enhance by fivefold in comparison with single phase system. Alternatively the alginate, agar and polyacrylamide matrix immobilized P. fluorescens-CS2 cells efficiently degraded ethylebenzene with enhanced efficiency compared to free cell cultures in single and two-phase systems. The cells entrapped in ployacrylamide and alginate were found to be stable and degradation efficient for a period of 42 days where as agar-entrapped P. fluorescens was stable and efficient a period of 36 days. This demonstrates that alginate and polyacrylamide matrices are more promising as compared to agar for cell immobilization.
TL;DR: Principal component analysis of the results obtained for the best yeast strains confirmed the importance of COD and total phenol reduction along with increase of organic nitrogen and final pH for the improvement of germination rates and phytotoxic reduction.
Abstract: A total of 105 yeast strains were isolated from Moroccan olive oil production plants and evaluated for their ability to grow in olive oil mill wastewaters (OMW). The 9 isolates that grew best on OMW were selected for further study to evaluate their effect on removal of organic pollutants and OMW phytotoxicity (barley seed germination test). The results showed that at least four yeast isolates effectively lowered the toxicity of this effluent in addition to providing very useful materials in terms of both yeast biomass (6 g/l DW) and an irrigation fluid. This group of yeast isolates significantly reduced the concentration of total phenols (44% removal) and Chemical Oxygen Demand, COD (63% removal). The best germination rate of 80% for undiluted OMW was obtained for strain Candida holstii that also increased the pH from 4.76 to 6.75. Principal component analysis of the results obtained for the best yeast strains confirmed the importance of COD and total phenol reduction along with increase of organic nitrogen and final pH for the improvement of germination rates and phytotoxic reduction. This study has highlighted the potential of indigenous yeasts in detoxification of olive mill wastewaters.
TL;DR: The fungal consortium was effective in converting high silica paddy straw into nutritionally rich compost thereby leading to economical and environment friendly disposal of this crop residue.
Abstract: Out of 10 thermophilic fungi isolated from wheat straw, farm yard manure, and soil, only three showed highest cellobiase, carboxymethyl cellulase, xylanase, and FPase activities. They were identified as Aspergillus nidulans (Th4), Scytalidium thermophilum (Th5), and Humicola sp. (Th10). A fungal consortium of these three fungi was used to compost a mixture (1:1) of silica rich paddy straw and lignin rich soybean trash. The composting of paddy straw for 3 months, during summer period in North India, resulted in a product with C:N ratio 9.5:1, available phosphorus 0.042% and fungal biomass 6.512 mg of N-acetyl glucosamine/100 mg of compost. However, a C:N ratio of 10.2:1 and highest humus content of 3.3% was achieved with 1:1 mixture of paddy straw and soybean trash. The fungal consortium was effective in converting high silica paddy straw into nutritionally rich compost thereby leading to economical and environment friendly disposal of this crop residue.
TL;DR: Microscopic analyses of the biofilm revealed diverse microbial morphologies, while Denaturing Gradient Gel Eletrophoresis (DGGE) profiling showed variations in the population of total bacteria and sulphate-reducing bacteria (SRB).
Abstract: The purpose of this work was to assess the degradation of linear alkylbenzene sulfonate (LAS) in a horizontal-flow anaerobic immobilized biomass (HAIB) reactor. The reactor was filled with polyurethane foam where the sludge from a sanitary sewage treatment was immobilized. The hydraulic detention time (HDT) used in the experiments was of 12 h. The reactor was fed with synthetic substrate (410 mg l−1 of meat extract, 115 mg l−1 of starch, 80 mg l−1 of saccharose, 320 mg l−1 of sodium bicarbonate and 5 ml l−1 of salt solution) in the following stages of operation: SI—synthetic substrate, SII—synthetic substrate with 7 mg l−1 of LAS, SIII—synthetic substrate with 14 mg l−1 of LAS and SIV—synthetic substrate containing yeast extract (substituting meat extract) and 14 mg l−1 of LAS, without starch. At the end of the experiment (313 days) a degradation of ∼35% of LAS was achieved. The higher the concentration of LAS, the greater the amount of foam for its adsorption. This is necessary because the isotherm of LAS adsorption in the foam is linear for the studied concentrations (2 to 50 mg l−1). Microscopic analyses of the biofilm revealed diverse microbial morphologies, while Denaturing Gradient Gel Eletrophoresis (DGGE) profiling showed variations in the population of total bacteria and sulphate-reducing bacteria (SRB). The 16S rRNA gene sequencing and phylogenetic analyses revealed that the members of the order Clostridiales were the major components of the bacterial community in the last reactor operation step.
TL;DR: A bacterial isolate belonging to the Halomonas genus was obtained from Soap Lake, a chemically stratified alkaline lake located in central Washington State, and the ability of this isolate to reduce Cr(VI) and Fe(III) was assessed under alkaline (pH = 9), anoxic, non-growth conditions with acetate as an electron donor.
Abstract: Hexavalent chromium is one of the most widely distributed environmental contaminants. Given the carcinogenic and mutagenic consequences of Cr(VI) exposure, the release of Cr(VI) into the environment has long been a major concern. While many reports of microbial Cr(VI) reduction are in circulation, very few have demonstrated Cr(VI) reduction under alkaline conditions. Since Cr(VI) exhibits higher mobility in alkaline soils relative to pH neutral soils, and since Cr contamination of alkaline soils is associated with a number of industrial activities, microbial Cr(VI) reduction under alkaline conditions requires attention.Soda lakes are the most stable alkaline environments on earth, and contain a wide diversity of alkaliphilic organisms. In this study, a bacterial isolate belonging to the Halomonas genus was obtained from Soap Lake, a chemically stratified alkaline lake located in central Washington State. The ability of this isolate to reduce Cr(VI) and Fe(III) was assessed under alkaline (pH = 9), anoxic, non-growth conditions with acetate as an electron donor. Metal reduction rates were quantified using Monod kinetics. In addition, Cr(VI) reduction experiments were carried out in the presence of Fe(III) to evaluate the possible enhancement of Cr(VI) reduction rates through electron shuttling mechanisms. While Fe(III) reduction rates were slow compared to previously reported rates, Cr(VI) reduction rates fell within range of previously reported rates.
TL;DR: The results indicate that microorganisms of the sweet flag rhizosphere can play an important role in the bioremediation of atrazine-contaminated sites.
Abstract: In presented study the capability of microorganisms isolated from the rhizosphere of sweet flag (Acorus calamus) to the atrazine degradation was assessed Following isolation of the microorganisms counts of psychrophilic bacteria, mesophilic bacteria and fungi were determined Isolated microorganisms were screened in terms of their ability to decompose a triazine herbicide, atrazine Our results demonstrate that within the rhizosphere of sweet flag there were 38 × 107 cfu of psychrophilic bacteria, 18 × 107 cfu of mesophilic bacteria, and 6 × 105 cfu of fungi per 1 g of dry root mass These microorganisms were represented by more than 20 different strains, and at the first step these strains were grown for 5 days in the presence of atrazine at a concentration of 5 mg/l In terms of the effect of this trial culture, the bacteria reduced the level of atrazine by an average of about 2–20%, but the average level of reduction by fungi was in the range 18–60% The most active strains involved in atrazine reduction were then selected and identified These strains were classified as Stenotrophomonas maltophilia, Bacillus licheniformis, Bacillus megaterium, Rahnella aquatilis (three strains), Umbelopsis isabellina, Volutella ciliata and Botrytis cinerea Culturing of the microorganisms for a longer time resulted in high atrazine degradation level The highest degradation level was observed at atrazine concentrations of 5 mg/l for S maltophilia (835% after 15 days of culture) and for Botrytis sp (82% after 21 days of culture) Our results indicate that microorganisms of the sweet flag rhizosphere can play an important role in the bioremediation of atrazine-contaminated sites
TL;DR: The results suggest that some contaminated soils in the tropics may contain exotic micro-organisms whose abilities and potentials are previously unknown and enhance the potential use of bioremediation as an effective tool for cleanup of PCB-contaminated soils.
Abstract: Contaminated sites in Lagos, Nigeria were screened for the presence of chlorobiphenyl-degrading bacteria. The technique of continual enrichment on Askarel fluid yielded bacterial isolates able to utilize dichlorobiphenyls (diCBs) as growth substrates and six were selected for further studies. Phenotypic typing and 16S rDNA analysis classified these organisms as species of Enterobacter, Ralstonia and Pseudomonas. All the strains readily utilized a broad spectrum of xenobiotics as sole sources of carbon and energy. Growth was observed on all monochlorobiphenyls (CBs), 2,2'-, 2,3-, 2,4'-, 3,3'- and 3,5-diCB as well as di- and trichlorobenzenes Growth was also sustainable on Askarel electrical transformer fluid and Aroclor 1221. Time-course studies using 100 ppm of 2-, 3- or 4-CB resulted in rapid exponential increases in cell numbers and CB transformation to respective chlorobenzoates (CBAs) within 70 h. Significant amounts of chloride were recovered in culture media of cells incubated with 2-CB and 3-CB, suggesting susceptibilities of both 2- and 3-chlorophenyl rings to attack, while the 4-CB was stoichiometrically transformed to 4-CBA. Extensive degradation of most of the congeners in Aroclor 1221 was observed when isolates were cultivated with the mixture as a sole carbon source. Aroclor 1221 was depleted by a minimum of 51% and maximum of 71%. Substantial amounts of chloride eliminated from the mixture ranged between 15 and 43%. These results suggest that some contaminated soils in the tropics may contain exotic micro-organisms whose abilities and potentials are previously unknown. An understanding of these novel strains therefore, may help answer questions about the microbial degradation of polychlorinated biphenyls (PCBs) in natural systems and enhance the potential use of bioremediation as an effective tool for cleanup of PCB-contaminated soils.
TL;DR: Inclusion of 0.5 μM Ni (dosed as NiCl2) to the influent from day 165 onwards lead to the recovery of the methanol removal efficiency to 99% without VFA accumulation within 2 days of bioreactor operation.
Abstract: The effect of nickel deprivation from the influent of a mesophilic (30°C) methanol fed upflow anaerobic sludge bed (UASB) reactor was investigated by coupling the reactor performance to the evolution of the Methanosarcina population of the bioreactor sludge. The reactor was operated at pH 7.0 and an organic loading rate (OLR) of 5–15 g COD l−1 day−1 for 191 days. A clear limitation of the specific methanogenic activity (SMA) on methanol due to the absence of nickel was observed after 129 days of bioreactor operation: the SMA of the sludge in medium with the complete trace metal solution except nickel amounted to 1.164 (±0.167) g CH4-COD g VSS−1 day−1 compared to 2.027 (±0.111) g CH4-COD g VSS−1 day−1 in a medium with the complete (including nickel) trace metal solution. The methanol removal efficiency during these 129 days was 99%, no volatile fatty acid (VFA) accumulation was observed and the size of the Methanosarcina population increased compared to the seed sludge. Continuation of the UASB reactor operation with the nickel limited sludge lead to incomplete methanol removal, and thus methanol accumulation in the reactor effluent from day 142 onwards. This methanol accumulation subsequently induced an increase of the acetogenic activity in the UASB reactor on day 160. On day 165, 77% of the methanol fed to the system was converted to acetate and the Methanosarcina population size had substantially decreased. Inclusion of 0.5 μM Ni (dosed as NiCl2) to the influent from day 165 onwards lead to the recovery of the methanol removal efficiency to 99% without VFA accumulation within 2 days of bioreactor operation.
TL;DR: The values of theactivation energy of the decolorization reaction (Ea) were found to depend on both the organism and the temperature range, and the possible reasons for the observed abrupt change of the activation energy were discussed.
Abstract: Studied was the effect of temperature in the range 12–46 °C on the rate of bacterial decolorization of the mono-azo dye Acid Orange 7 by Alcaligenes faecalis 6132 and Rhodococcus erythropolis 24. With both strains the raise of temperature led to a corresponding raise of decolorization rate better manifested by R. erythropolis. The analysis of the Arrhenius plot revealed a break near the middle of the temperature range. The regression analysis showed practically complete identity of the observed break point temperatures (T
BP): 20.7 °C for Alc. faecalis and 20.8 °C for R. erythropolis. The values of the activation energy of the decolorization reaction (E
a) were found to depend on both the organism and the temperature range. In the range below T
BP the estimated values of E
a were 138 ± 7 kJ mol−1 for Alc. faecalis and 160 ± 8 kJ mol−1 for R. erythropolis. In the range above T
BP they were 54.2 ± 1.8 kJ mol−1 for Alc. faecalis and 37.6 ± 4.1 kJ mol−1 for R. erythropolis. Discussed are the possible reasons for the observed abrupt change of the activation energy.