Degradation of hydrocarbons and their derivatives by a microbial association on the base of Canadian pondweed

The degrading action of an aquatic plant-microbial association on the base of Canadian pondweed (Elodea canadensis) and its components (sterilized plant and two periphytonic strains, Pseudomonas fluorescens El-2.1 and Brevundimonas diminuta El-3.1) on crude oil, the water-soluble crude oil fraction, and individual test compounds (phenol, toluene, benzene, decalin, and naphthalene) was studied. It was found that the native association had a wider range and higher degree of degrading activity than individual species. Bacterial strains were significantly more active only towards naphthalene. The ability of the sterilized plant to degrade crude oil and phenol was no less than that of microorganisms and much more for toluene. Enzymatic activity towards the pollutants studied was found in E. canadensis exudates and buffer extracts of its cells.     

Degradation of mineral oils by a selected microbial association

A series of microbial associations capable of degrading various petroleum oils, emulsols, and crude oil were obtained by selection during periodic or continuous cultivation. The formation of these associations and oil-product degradation occurred most efficiently during aerobic flow cultivation. Under these conditions, oils were degraded by 92% on average. The microbial degradation of a petroleum oil depended on its brand, concentration, emulsification, and aeration.     

Degradation of paracetamol by pure bacterial cultures and their microbial consortium

Three bacterial strains utilizing paracetamol as the sole carbon, nitrogen, and energy source were isolated from a paracetamol-degrading aerobic aggregate, and assigned to species of the genera Stenotrophomonas and Pseudomonas. The Stenotrophomonas species have not included any known paracetamol degraders until now. In batch cultures, the organisms f1, f2, and fg-2 could perform complete degradation of paracetamol at concentrations of 400, 2,500, and 2,000 mg/L or below, respectively. A combination of three microbial strains resulted in significantly improved degradation and mineralization of paracetamol. The co-culture was able to use paracetamol up to concentrations of 4,000 mg/L, and mineralized 87.1 % of the added paracetamol at the initial of 2,000 mg/L. Two key metabolites of the biodegradation pathway of paracetamol, 4-aminophenol, and hydroquinone were detected. Paracetamol was degraded predominantly via 4-aminophenol to hydroquinone with subsequent ring fission, suggesting new pathways for paracetamol-degrading bacteria. The degradation of paracetamol could thus be performed by the single isolates, but is stimulated by a synergistic interaction of the three-member consortium, suggesting a possible complementary interaction among the various isolates. The exact roles of each of the strains in the consortium need to be further elucidated.     

Detection of halogenated hydrocarbons by a microbial sensorsystem using a stop-flow-technique

To improve the applicability and efficiency of the microbial assay developed by W. Hutter, J. Peter, H. Swoboda, W. Hampel, E. Rosenberg, D. Krämer, and R. Kellner (1995) a stop-flow-technique was developed for the determination of halogenated hydrocarbons in water samples. Cells of Rhodococcus sp. DSM 6344 were immobilized in alginate beads and placed in a stirred flow-through reactor. The time of incubation, the bacterial cell density and the amount of alginate beads in the reactor on the response of the system as determined by the drop in EMF was investigated. Optimal conditions were achieved with 2 g beads containing a bacterial cell concentration of 0,1 g cells wet wt/g matrix and an incubation time of 20 min. Calibrations with chlorinated and brominated substrates like ethyl bromide, 1,2-dibromopropane, isobutyl bromide, 1-chlorobutane and 1,5-dichloropentane showed a non-linear dependence at low substrate concentrations. The detection limits for ethyl bromide and 1-chlorobutane were estimated as 0.02 mg/l and 0.45 mg/l, respectively, the relative standard deviation was below 10 %. The great advantage of the stop-flow-technique compared to discontinuous measurements can be seen in a simplified handling and an increase of sample capacity.     

Biodegradation of polycyclic aromatic hydrocarbons by a halophilic microbial consortium

In this study we investigated the phenanthrene degradation by a halophilic consortium obtained from a saline soil sample. This consortium, named Qphe, could efficiently utilize phenanthrene in a wide range of NaCl concentrations, from 1% to 17% (w/v). Since none of the purified isolates could degrade phenanthrene, serial dilutions were performed and resulted in a simple polycyclic aromatic hydrocarbon (PAH)-degrading culture named Qphe-SubIV which was shown to contain one culturable Halomonas strain and one unculturable strain belonging to the genus Marinobacter. Qphe-SubIV was shown to grow on phenanthrene at salinities as high as 15% NaCl (w/v) and similarly to Qphe, at the optimal NaCl concentration of 5% (w/v), could degrade more than 90% of the amended phenanthrene in 6 days. The comparison of the substrate range of the two consortiums showed that the simplified culture had lost the ability to degrade chrysene but still could grow on other polyaromatic substrates utilized by Qphe. Metabolite analysis by HPLC and GC–MS showed that 2-hydroxy 1-naphthoic acid and 2-naphthol were among the major metabolites accumulated in the Qphe-SubIV culture media, indicating that an initial dioxygenation step might proceed at C1 and C2 positions. By investigating the growth ability on various substrates along with the detection of catechol dioxygenase gene, it was postulated that the uncultured Marinobacter strain had the central role in phenanthrene degradation and the Halomonas strain played an auxiliary role in the culture by utilizing phenanthrene metabolites whose accumulation in the media could be toxic.     

Degradation of chlorophenols by a defined mixed microbial community

Synthetic sewage containing phenol, acetone, and alkanols plus 4-chlorophenol or a mixture of isomeric chlorophenols is completely degraded by a defined mixed culture with Pseudomonas sp. strain B13 as a chlorocatechol-dissimilating member of the community. Total degradation of the organic carbon was indicated by release of stoichiometric amounts of chloride and low content of dissolved organic carbon in the cell-free effluents. During adaptation to high loads of chlorophenols the initial meta-cleavage activity was completely replaced by ortho-cleavage activity of type I and II. In the fully acclimated culture, hybrid strains such as Alcaligenes sp. strain A7-2 were detected, which are more competitive than Pseudomonas sp. strain B13 with respect to chlorophenol degradation.     

一株假单胞菌HZ-1降解石油烃的初步研究

从石油废水活性污泥中分离到一株可以较好降解石油烃的假单胞菌（Pseudomonas sp）HZ-1,采用生物膜法对该菌株在30℃条件下降解某炼油厂废水中的烃类物质进行了研究.研究结果表明不同营养盐NH4NO3、NaH2PO4、NH4Cl对菌株HZ-1处理石油废水的作用不同,终浓度为1000mg/L的NH4NO3对菌株HZ-1处理石油废水效果最佳.并在30℃和pH 8.0的条件下,初步研究了该菌株降解萘的情况,在萘浓度低于78 mg/L的情况下,120 rpm好氧振荡培养144h,这株菌对萘的降解率在86%以上.     

Degradation of chlorophenols by a defined mixed microbial community.

Synthetic sewage containing phenol, acetone, and alkanols plus 4-chlorophenol or a mixture of isomeric chlorophenols is completely degraded by a defined mixed culture with Pseudomonas sp. strain B13 as a chlorocatechol-dissimilating member of the community. Total degradation of the organic carbon was indicated by release of stoichiometric amounts of chloride and low content of dissolved organic carbon in the cell-free effluents. During adaptation to high loads of chlorophenols the initial meta-cleavage activity was completely replaced by ortho-cleavage activity of type I and II. In the fully acclimated culture, hybrid strains such as Alcaligenes sp. strain A7-2 were detected, which are more competitive than Pseudomonas sp. strain B13 with respect to chlorophenol degradation.     

Degradation of unsaturated hydrocarbons by methanogenic enrichment cultures

Abstract The biodegradability of hydrocarbons under anaerobic conditions was studied in enrichment cultures using mineral media inoculated with sewage sludge or sediment samples of limnic and marine origin. No indication of methanogenic degradation was obtained with either n -hexane, n -hexadecane, n -heptadecane, 1-hexene, cis -2-hexene, trans -2-hexene, isoprene, 1-hexine, benzene, toluene, xylene, cyclohexene, cycloheptatriene, cyclopentadiene, styrene, naphthalene, azulene, or β-carotene. Squalene was incompletely converted to methane and carbon dioxide. Complete degradation was observed with 1-hexadecene. Methanogenic subcultures were maintained on 1-hexadecene and squalene. Both enrichments contained after several transfers Methanospirillum hungatei and Methanothrix soehngenii as prevalent methanogenic bacteria. Acetate (≤80 μ M) was the only intermediary product detected indicating that degradation proceeded via hydrogen-dependent syntrophic β-oxidations. Short rods on hexadecene and cocci on squalene were found to be associated with substrate degradation. The results indicate that terminal double bonds can be sufficient to allow methanogenic degradation of hydrocarbons whereas branching and terminal ring closures may significantly contribute to hydrocarbon stability in anoxic environments.     

铁还原菌降解石油烃的研究进展

铁还原菌是指能够利用细胞外Fe(III)作为末端电子受体,通过氧化有机物将Fe(III)还原为Fe(II)微生物的总称。铁还原作用广泛存在于土壤、河流、海洋、地表含水层以及高温高压的地下深部油藏。在厌氧或兼性厌氧条件下,Fe(III)还原耦合有机物的降解,对铁、碳元素的生物地球化学循环具有重要意义。本文介绍了铁还原菌的多样性和铁还原作用机理,综述了铁还原菌在石油烃降解方面的研究进展。此外,还总结了铁还原菌在生物修复中的潜在作用,并对未来的研究方向进行了展望。     

Degradation of biphenyl by methanogenic microbial consortium

Biphenyl was readily degraded and mineralized to CO₂ and CH₄ by a PCB-dechlorinating anaerobic microbial consortium. Degradation occurred when biphenyl was supplied as a sole source of carbon or as a co-metabolic substrate together with glucose and methanol. p-Cresol was detected and confirmed by mass spectroscopy as a transient intermediate. Production of ¹⁴ C-CO₂ and ¹⁴C-CH₄ from ¹⁴C-biphenyl was observed in the approximate ratio of 1:2. The results indicated the existence of novel pathways for biphenyl degradation in a natural anaerobic microbial community.     

Degradation of acetochlor by four microbial communities

Four microbial communities capable of degrading acetochlor, designated A, D, E, and J, were obtained from acetochlor-contaminated soil and sludge. Acetochlor at an initial concentration of 55mg/L was completely degraded by the four mixed cultures after 4 days. At 80 mg/L acetochlor, more than 99% degradation was observed with D, 84% with A and E, and 88% with J after 9 days. There are primary eight strains of bacteria in community A, three in community D, E, and J, respectively. No single isolate was able to degrade acetochlor efficiently. The acetochlor biodegradation products were identified by gas chromatography-mass spectrometry. The probable degradative pathways of acetochlor involved dechlorination, hydroxylation, deethoxymethylation, cyclization, carboxylation, and decarboxylation. Propachlor, alachlor, and metolachlor, which are also the main components of the chloroacetanilide herbicide, could be degraded by the four mixed cultures to some degree. Given the high degradation rates observed here, the four mixed cultures obtained may be useful in the degradation processes of acetochlor.     

Degradation of petroleum model compounds immobilized on clay by a hypersaline microbial mat

In this study the degradation of hydrophobic petroleum model compounds (phenanthrene, pristane, octadecane and dibenzothiophene) added to a submersed hypersaline microbial mat was investigated. Montmorillonite with an artificially altered, hydrophobic surface was used as carrier material, forming an organo-clay complex (OCC) with the attached mixture of petroleum model compounds. 6 mg/cm² OCC were applied to cyanobacterialmat pieces, containing 33.3 g/mg OCC of each compound. The degradationexperiment was performed under controlled laboratory conditions and accompanied bychemical analyses by GC/GC-MS, molecular analyses by PCR and DGGE as well asfunctional analyses by microsensor measurements of oxygen, photosynthesis, sulfide,pH and light. All applied model compounds were degraded, but residues were stillpresent after 18 weeks. The aromatic compounds phenanthrene (5.1 g/mg OCC)and dibenzothiophene (4.3 g/mg OCC) were preferentially degraded compared to the alkanes pristane (12.4 g/mg OCC) and n-octadecane (13.4 g/mg OCC). Metabolic changes during the degradation process could not be detected by microsensor measurements. The molecular population analyses did not reveal any significant community changes concomitant with the decrease of the petroleum model compounds. We conclude, that the pristine mats represent an intact, robust ecosystem in which the enzymatic requirements for the degradation of the applied pollutants exist. The slow degradation process did not affect the usual high internal turnover rates and did not favor a certain population in the community of the mats.     

The loss of electrolytes from leaves treated with hydrocarbons and their derivatives

Indices of the effects on the leaves of a number of plant species of members of homologous series of hydrocarbons and certain of their oil-soluble derivatives were based on changes in conductance of aqueous systems when hydrocarbon-treated leaves were added. The results were compared with previous phytotoxicity studies where hydrocarbons were applied to plants in vapour and in aqueous treatments. A relationship between the conductance changes and the physical properties of the applied hydrocarbons is suggested. The presumed effects on cell membrane permeability indicated by the conductance changes agreed with known susceptibility of different plant species towards hydrocarbons of different homologous series applied in the liquid state.     

Degradation of carbazole and its derivatives by a Pseudomonas sp.

Carbazole, carbazoles with monomethyl or dimethyls substituted on different positions (C₁-carbazoles or C₂-carbazoles), and benzocarbazoles, as toxic and mutagenic components of petroleum and creosote contamination, were biodegradable by an isolated bacterial strain Pseudomonas sp. XLDN4-9. C₁-carbazoles were degraded in preference to carbazole and C₂-carbazoles. The biodegradation of C₁-carbazoles or C₂-carbazoles was influenced by the positions of methyl substitutions. Among C₁-carbazole isomers, 1-methyl carbazole was the most susceptible. C₂-carbazole isomers with substitutions on the same benzo-nucleus were more susceptible at a concentration of less than 3.4 μg g⁻¹ petroleum, especially when harboring one substitution on position 1. In particular, 1,5-dimethyl carbazole was the most recalcitrant dimethyl isomer.     

Degradation of aromatic hydrocarbons by white-rot fungi in a historically contaminated soil

Phanerochaete chrysosporium NRRL 6361 and Pleurotus pulmonarius CBS 664.97 were tested for their ability to grow under nonsterile conditions and to degrade various aromatic hydrocarbons in an aged contaminated soil that also contained high concentrations of heavy metals. After 24 days fungal incubation, carbon-CO2 liberated, an indicator of microbial activity, reached a plateau. At the end of the incubation time (30 days), fungal colonization was clearly visible and was confirmed by ergosterol and cell organic carbon determinations. In spite of unfavorable pH (around 7.4) and the presence of heavy metals, both fungi produced Mn-peroxidase activity. In contrast, laccase and aryl-alcohol oxidase were detected only in the soil treated with P. pulmonarius CBS 664.97 and lignin-peroxidase in that with P. chrysosporium NRRL 6361. No lignin-modifying enzyme activities were present in non-inoculated soil incubated for 30 days (control microcosm). Regardless of the fungus employed, a total removal of naphtalene, tetrachlorobenzene, and dichloroaniline isomers, diphenylether and N-phenyl-1-naphtalenamine, was observed. Significant release of chloride ions was also observed in fungal-treated soil, in comparison with that recorded in the control microcosm. Both fungi led to a significant decrease in soil toxicity, as assessed using two different soil contact assays, including the Lepidium sativum L. germination test and the Collembola mortality test.     

Degradation of polycyclic aromatic hydrocarbons in soil by a two-step sequential treatment

The objectives of this work were to isolate the microorganisms responsible for a previously observed degradation of polycyclic aromatic hydrocarbons (PAH) in soil and to test a method for cleaning a PAH-contaminated soil. An efficient PAH degrader was isolated from an agricultural soil and designated as Mycobacterium LP1. In liquid culture, it degraded phenanthrene (58%), pyrene (24%), anthracene (21%) and benzo(a)pyrene (10%) present in mixture (initial concentration 50 μg ml⁻¹ each) and phenanthrene (92%) and pyrene (94%) as sole carbon sources after 14 days of incubation at 30°C. In soil, Mycobacterium LP1 mineralised ¹⁴C-phenanthrene (45%) and ¹⁴C-pyrene (65%) after 10 days. The good ability of this Mycobacterium was combined with the benzo(a)pyrene oxidation effect obtained by 1% w/w rapeseed oil in a sequential treatment of a PAH-spiked soil (total PAH concentration 200 mg kg⁻¹). The first step was incubation with the bacterium for 12 days and the second step was the addition of the rapeseed oil after this time and a further incubation of 22 days. Phenanthrene (99%), pyrene (95%) and anthracene (99%) were mainly degraded in the first 12 days and a total of 85% of benzo(a)pyrene was transformed during the whole process. The feasibility of the method is discussed.     

降解石油基塑料的微生物及微生物菌群

伴随着环境污染的日益严重,处理"白色污染"成为人们面临的一个棘手难题,而各种合成塑料因为应用广泛且很难降解成为其"主要元凶"。利用自然界存在的或者是进化产生的微生物可降解合成塑料是一种环境友好型的策略。以国家自然科学基金国际(地区)合作和交流(中欧组织间合作研究NSFC-EU)项目"合成塑料降解转化微生物菌群"为基础,总结近年来筛选到的能够降解合成塑料,如聚乙烯(Polyethylene,PE)、聚丙烯(Polypropylene,PP)、聚苯乙烯(Polystyrene,PS)、聚氯乙烯(Polyvinyl chloride,PVC)、聚氨酯(Polyurethane,PUR)、聚对苯二甲酸乙二醇酯(Polyethylene terephthalate,PET)的纯细菌、纯真菌及微生物菌群的研究状况,分析了各种微生物在石油基塑料降解中的作用,讨论了微生物及其降解酶对合成塑料降解研究的优缺点。     

Degradation of meta-trifluoromethylbenzoate by sequential microbial and photochemical treatments

Abstract m - and p -trifluoromethyl (TFM)-benzoates are completely degraded by aerobic bacteria that catabolize alkylbenzoates; biodegradation ceases after ring-fission with the accumulation of a trifluoromethyl muconate semialdehyde (2-hydroxy-6-oxo-7,7,7-trifluorohepta-2,4-dienoate, TFHOD) which is resistant to biochemical attack. A bacterium (Strain V-1), isolated from sea-water, grew aerobically on benzoate or m -toluate. Cells grown on benzoate or m -toluate oxidized both compounds at similar relative rates. Catabolism involved benzoate 1,2-dioxygenase (decarboxylating) and meta -cleavage to yield muconate semialdehydes. Cells grown on benzoate metabolized m -TFM-benzoate to TFHOD. The ring-fission products from m -toluate and TFHOD were degraded by sunlight, and equimolar fluoride was released from TFHOD. Sequential biochemical and photochemical treatment allowed the destruction of m -TFM-benzoate beyond the biochemically recalcitrant intermediate TFHOD.