Biodegradation of crosslinked acrylic polymers by a white-rot fungus

Two synthetic superabsorbent crosslinked acrylic polymers were mineralized by the white-rot fungusPhanerochaete chrysosporium. The amount of polymer converted to CO₂ increased as the amount of polymer added to the cultures increased. In the presence of sufficiently large amounts of the superabsorbents, such that all of the culture fluid was absorbed and a gelatinous matrix was formed, the fungus still grew and mineralization was observed. Neither the polymers, nor their degradation products were toxic to the fungus. While the rates of mineralization were low, all of the polymers incubated in the liquid fungal cultures were completely depolymerized to water soluble products within 15–18 days. The depolymerization of the polymers was observed only in nitrogen limited cultures of the fungus which secrete the lignin degradation system, however, the water soluble products of depolymerization were mineralized in both nutrient limited and sufficient cultures of the fungus. The rate of mineralization of the depolymerized metabolites was more than two times greater in nutrient sufficient cultures. Following longer incubation periods, most (> 80 %) of the radioactivity was recovered in the fungal mycelial mat suggesting that carbon of the polymer had been converted to fungal metabolites.     

Biodegradation of sucrose poly fatty acid esters in soils

Sucrose polyesters (SPEs) were applied to soil at rates equivalent to 1062 to 1293 kg per hectare and incubated over periods of 100 to 403 days at 20 ± 2°C in darkness and at a soil moisture of 40 % of the maximum water holding capacity. All applied forms of SPEs were aerobically biodegraded to some degree in both American and German soil. However, the mineralization rates varied considerably and were dependent on both SPE and soil type. For example, sucrose octaoleate underwent slow and limited mineralization in the German soils Speyer and Borstel as well as in the American soil Madera, reaching only 6.9 – 18.4 % mineralisation after over 400 days incubation. The same material in the American soils Hollande, Thermal and Uvalde as well as in the German soil Speicherkoog, reached 35–52 % after the same incubation period. Of the SPEs most realistic for use in food products, the more liquid (i.e. with the least saturated fatty acids) underwent the most rapid and extensive mineralization. However, the mineralization rates for these materials were distinctly lower than the corresponding ones for sucrose octaoleate. In all cases the extent of mineralization of the SPEs in soil was significantly lower than that of a control fat (synthetic triglyceride mixture HB307), which typically underwent over 50 % mineralization in 60 days.

As field conditions would be considerably different to those in the laboratory (due to the presence of microbially acclimatised sewage sludge, fluctuations in soil temperature and moisture, and contamination by ecotoxic pollutants) it is difficult to predict accurately, on the basis of laboratory results, the likely rate of mineralization of SPEs in the field. However, this study does suggest that the more solid the SPE, the more likely it is to persist, and possibly accumulate, following application to soil.     

一株木材腐朽菌及其粗酶液对七氯的降解

Phlebia acanthocystis TMIC34875是一株具有七氯降解能力的木材腐朽菌。为利用微生物技术去除环境中的七氯残留提供理论依据,研究了该菌株及其粗酶液对七氯的降解性能及其动力学特性。结果表明,菌株在七氯的初始浓度为50μmol/L时具有最大降解速率,为0.3031μmol/（L·h）;而菌体接种量为15%时,降解速率达到最高,为0.2045μmol/（L·h）。降解酶定位研究表明,七氯的降解主要是胞内酶在起作用。七氯胞内酶降解的酶促反应最适温度是35℃,在30-40℃之间有较高的催化活性;最适pH值为5.0,在pH 4.5-6.0之间有较高的催化活性,最适条件下反应1 h后七氯的降解率为65%。胞内粗酶液降解七氯的米氏常数K m为5.42μmol/L,最大反应速率V max为4.55μmol/min。胞内酶处理体系的GC/MS图谱显示,主要降解产物为1-羟基六氯、1-羟基-2,3-环氧六氯和环氧七氯,表明胞内酶对七氯的初始代谢机理同菌株相似,均是通过环氧化和置换反应来完成的。     

Biodegradation of carbofuran in soils within Nzoia River Basin,Kenya

Carbofuran (2,3-dihydro-2,2-dimethylbenzofuran-7-yl methylcarbamate) has been used within the Nzoia River Basin (NRB), especially in Bunyala Rice Irrigation Schemes, in Kenya for the control of pests. In this study, the capacity of native bacteria to degrade carbofuran in soils from NRB was investigated. A gram positive, rod-shaped bacteria capable of degrading carbofuran was isolated through liquid cultures with carbofuran as the only carbon and nitrogen source. The isolate degraded 98% of 100-μg mL^?1 carbofuran within 10 days with the formation of carbofuran phenol as the only detectable metabolite. The degradation of carbofuran was followed by measuring its residues in liquid cultures using high performance liquid chromatography (HPLC). Physical and morphological characteristics as well as molecular characterization confirmed the bacterial isolate to be a member of Bacillus species. The results indicate that this strain of Bacillus sp. could be considered as Bacillus cereus or Bacillus thuringiensis with a bootstrap value of 100% similar to the 16S rRNA gene sequences. The biodegradation capability of the native strains in this study indicates that they have great potential for application in bioremediation of carbofuran-contaminated soil sites.     

Biodegradation of alpha and beta isomers of endosulphan and endosulphan sulphate in Indian soils

The degradation of alpha and beta isomers of endosulphan and endosulphan sulphate in four sterilized and non sterilized Indian soils under laboratory conditions was studied. Degradation was found to be more in non-sterilized as compared to the sterilized soil. The half life of alpha-endosulphan, beta-endosulphan and endosulphan sulphate was found to be 136.8, 273 and 301 days in sterilized Alfisol and 55, 256 and 277 days in non-sterilized Alfisol,respectively. Alpha-endosulphan degraded more readily than beta-endosulphan and endosulphan sulphate under both sterilized and non-sterilized soil conditions.     

Degradation of CL-20 by white-rot fungi

In previous studies, we found that the emerging energetic chemical, CL-20 (C6H6N12O12, 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane), can be degraded following its initial denitration using both aerobic and anaerobic bacteria. The C and N mass balances were not determined due to the absence of labeled starting compounds. The present study describes the degradation of the emerging contaminant by Phanerochaete chrysosporium using ring-labeled [15N]-CL-20 and [14C]-CL-20. Ligninolytic cultures degraded CL-20 with the release of nitrous oxide (N2O) in amounts corresponding to 45% of the nitrogen content of CL-20. When ring-labeled [15N]-CL-20 was used, both 14N14NO and 15N14NO were observed, likely produced from -NO2 and N-NO2, respectively. The incubation of uniformly labeled [14C]-CL-20 with fungi led to the production of 14CO2 (> 80%). Another ligninolytic fungus, Irpex lacteus, was also able to degrade CL-20, but as for P. chrysosporium, no early intermediates were observed. When CL-20 was incubated with manganese peroxidase (MnP), we detected an intermediate with a [M-H]- mass ion at 345 Da (or 351 and 349 Da when using ring-labeled and nitro-labeled [15N]-CL-20, respectively) matching a molecular formula of C6H6N10O8. The intermediate was thus tentatively identified as a doubly denitrated CL-20 product. The concomitant release of nitrite ions (NO2-) with CL-20 degradation by MnP also supported the occurrence of an initial denitration prior to cleavage and decomposition.     

Biodegradation of aromatic compounds by white rot and ectomycorrhizal fungal species and the accumulation of chlorinated benzoic acid in ectomycorrhizal pine seedlings

The capability of different white rot (WR, Heterobasidion annosum, Phanerochaete chrysosporium, Trametes versicolor) and ectomycorrhizal (ECM, Paxillus involutus, Suillus bovinus) fungal species to degrade different aromatic compounds and the absorption of 3-chlorobenzoic acid (3-CBA) by ECM pine seedlings was examined. The effect of aromatic compounds on the fungal biomass development varied considerably and depended on (a) the compound, (b) the external concentration, and (c) the fungal species. The highest effect on the fungal biomass development was observed for 3-CBA. Generally the tolerance of WR fungi against aromatic compounds was higher than that of the biotrophic fungal species. The capability of different fungi to degrade aromatic substances varied between the species but not generally between biotrophic and saprotrophic fungi. The highest degradation capability for aromatic compounds was detected for T. versicolor and H. annosum, whereas for Phanerochaete chrysosporium and the ECM fungi lower degradation rates were found. However, Paxillus involutus and S. bovinus showed comparable degradation rates at low concentrations of benzoic acid and 4-hydroxybenzoic acid. In contrast to liquid cultures, where no biodegradation of 3-CBA by S. bovinus was observed, mycorrhizal pines inoculated with S. bovinus showed a low capability to remove 3-CBA from soil substrates. Additional X-ray microanalytical investigations showed, that 3-CBA supplied to mycorrhizal plants was accumulated in the root cell cytoplasm and is translocated across the endodermis to the shoot of mycorrhizal pine seedlings.     

Biodegradation of s-triazine herbicide atrazine by Enterobacter cloacae and Burkholderia cepacia sp. from long-term treated sugarcane-cultivated soils in Kenya

In this study soils from sugarcane-cultivated fields were screened for bacterial species capable of atrazine (6-chloro-N²-ethyl-N⁴-isopropyl-1,3,5-triazine-2,4-diamine) degradation due to long exposure of the soils to this herbicide. To enrich for atrazine degraders, Minimal Salt Medium containing atrazine as the sole N source and glucose as the C source was inoculated with soils impacted with this herbicide and incubated. Bacterial growth was monitored by measuring optical density. The degradation of atrazine was followed by measuring residual atrazine in liquid cultures over a given time period by high performance liquid chromatography. Bacterial strains isolated from the enrichment cultures were characterized by biochemical tests and identified by 16S rRNA gene sequencing. Two bacterial strains coded ISL 8 and ISL 15 isolated from two different fields were shown to have 94 and 96% 16S rRNA gene sequence similarity to Burkholderia cepacia respectively. Another bacterial sp., ISL 14 was closely related to Enterobacter cloacae with a 96% 16S rRNA gene sequence similarity. There was not much difference between the extents of atrazine degradation by the enrichment cultures with communities (79–82% applied amount) from which pure strains were isolated and the pure strains themselves in liquid cultures that showed a degradation of 53–83% of applied amount. The study showed existence of bacterial strains in different sugarcane-cultivated fields which can use atrazine as a nitrogen source. The bacterial strains isolated can be used to enhance the degradation of atrazine in contaminated soils where atrazine is still considered to be recalcitrant.     

Biodegradation of s-triazine herbicide atrazine by Enterobacter cloacae and Burkholderia cepacia sp. from long-term treated sugarcane-cultivated soils in Kenya

In this study soils from sugarcane-cultivated fields were screened for bacterial species capable of atrazine (6-chloro-N2-ethyl-N?-isopropyl-1,3,5-triazine-2,4-diamine) degradation due to long exposure of the soils to this herbicide. To enrich for atrazine degraders, Minimal Salt Medium containing atrazine as the sole N source and glucose as the C source was inoculated with soils impacted with this herbicide and incubated. Bacterial growth was monitored by measuring optical density. The degradation of atrazine was followed by measuring residual atrazine in liquid cultures over a given time period by high performance liquid chromatography. Bacterial strains isolated from the enrichment cultures were characterized by biochemical tests and identified by 16S rRNA gene sequencing. Two bacterial strains coded ISL 8 and ISL 15 isolated from two different fields were shown to have 94 and 96% 16S rRNA gene sequence similarity to Burkholderia cepacia respectively. Another bacterial sp., ISL 14 was closely related to Enterobacter cloacae with a 96% 16S rRNA gene sequence similarity. There was not much difference between the extents of atrazine degradation by the enrichment cultures with communities (79-82% applied amount) from which pure strains were isolated and the pure strains themselves in liquid cultures that showed a degradation of 53-83% of applied amount. The study showed existence of bacterial strains in different sugarcane-cultivated fields which can use atrazine as a nitrogen source. The bacterial strains isolated can be used to enhance the degradation of atrazine in contaminated soils where atrazine is still considered to be recalcitrant.     

Mechanistics of trichloroethylene mineralization by the white-rot fungus Trametes versicolor

The white-rot fungus Trametes versicolor degraded trichloroethylene (TCE), a highly oxidized chloroethene, and produced 2,2,2-trichloroethanol and carbon dioxide as the main products of degradation, based on the results obtained using [13C]-TCE as the substrate. For a range of concentrations of TCE between 2 and 20 mg l(-1), 53% of the theoretical maximum chloride expected from complete degradation of TCE was observed. Laccase was shown to be induced by TCE, but did not appear to play a role in TCE degradation. Cytochrome P-450 appears to be involved in TCE degradation, as evidenced by marked inhibition of degradation of TCE in the presence of 1-aminobenzotriazole, a known inhibitor of cytochrome P-450. Our results suggested that chloral (trichloroacetaldehyde) was an intermediate of the TCE degradation pathway. The results indicate that the TCE degradation pathway in T. versicolor appears to be similar to that previously reported in mammals and is mechanistically quite different from bacterial TCE degradation.     

Biodegradation of fluoranthene by soil fungi

A selection of 39 strains of micromycetes known as good degraders of polychlorinated aromatic compounds, mostly isolated from soil and belonging to various taxonomic groups, have been investigated for fluoranthene degradation. Toxicity assays, first evaluated on solid medium MEA, have not shown any toxicity of fluoranthene (1-100 mg.L-1) towards fungi. Whereas, consumption assays on a solid synthetic medium showed a toxicity at 100 mg.L-1. The degradation of fluoranthene (10 mg.L-1) was then investigated in a liquid synthetic medium for 4 days and evaluated by HPLC. Among the 39 strains tested, 18 degraded fluoranthene at 60% or more. Zygomycetes appeared to be the most efficient group (mean degradation: 90%). Among 18 performant strains, 10 had not yet been reported in the literature: Sporormiella australis, Cryptococcus albidus, Cicinobolus cesatii, Pestalotia palmarum, beauveria alba, Aspergillus terreus. Cunninghamella blakesleeana, C. echinulata, Mortierella ramanniana and Rhizopus arrhizus. Fluoranthene adsorption on fungi was very low for the strains which degraded well fluoranthene (mean adsorption: 4%). Whereas, some strains adsorbed it much more such as Colletotrichum dematium (47%) and Penicillium italicum (43%).     

Oxidative dechlorination of methoxychlor by ligninolytic enzymes from white-rot fungi

Ligninolytic enzymes, manganese peroxidase (MnP), laccase, and lignin peroxidase (LiP), from white-rot fungi were used in an attempt to treat methoxychlor (MC), a chemical widely used as a pesticide. MnP and laccase in the presence of Tween 80 and 1-hydroxybenzotriazole (HBT), respectively, and LiP were found to degrade MC, and MnP-Tween 80 decreased MC levels by about 65% after a 24-h treatment. MC was converted into methoxychlor olefin (MCO) and 4,4'-dimethoxybenzophenone by MnP-Tween 80 or laccase-HBT treatment. These results indicate that ligninolytic enzymes from white-rot fungi can catalyze the oxidative dechlorination of MC. Moreover, a metabolite MCO was also degraded by MnP-Tween 80 or laccase-HBT treatment.     

白腐菌处理染料废水的研究进展

白腐菌是一种可有效处理染料废水的丝状真菌 ,它可通过其分泌的特殊的降解酶系或其他机制将各种人工合成的染料彻底降解为CO2 和H2 O ,同时 ,对脱色具有良好的作用。本文就白腐菌的生物学特性及其对染料的降解酶系、机理和白腐菌发酵的主要影响因子、白腐菌处理染料废水的有关研究及应用现状进行了综述     

硝化细菌对碘普罗胺的降解及作用机制

将富含硝化细菌的驯化污泥投放于培养基中,以碘普罗胺(IOPr)为处理对象,研究硝化细菌对IOPr的降解促进作用情况。结果表明,富集培养的硝化细菌能有效地促进IOPr的降解,最佳反应条件为:温度30℃,pH 8.0~8.5,初始投加浓度为10 mg/L,同时在硝化细菌存在条件下,IOPr的5 d降解率可达84.1%。IOPr的生物降解属于共代谢机制,向培养基中加入葡萄糖、可溶性淀粉和麦芽糖,可以显著提高IOPr的降解去除率;在投加500 mg/L葡萄糖作为外加碳源时,硝化细菌对IOPr的3 d降解率可达60.3%。     

Biodegradation of pyrene by sediment fungi

Micromycetes were isolated from PAHS-contaminated sediment and identified. They were investigated for pyrene degradation (10 mg l-1) in liquid synthetic medium for two days. Among the 41 strains isolated, 10 highly degraded pyrene (> 2.4 mg g-1 dry weight): two Zygomycetes (Mucor racemosus, M. racemosus var. sphaerosporus), 6 Deuteromycetes (Gliocladium virens, Penicillium simplicissimum, P. janthinellum, Phialophora alba, P. hoffmannii, Trichoderma harzianum), a Dematiaceae (Scopulariopsis brumptii) and a Sphaeropsidale (Coniothyrium fuckelii). Zygomycetes appeared as one of the most efficient taxonomic groups, especially with Mucor racemosus. Penicillium crustosum was the only strain that did not degrade pyrene. Among the 10 fungi which were performant for pyrene degradation, nine were not yet reported in the literature and showed a real value for PAH remediation.     

嗜热栖热菌降解氟喹诺酮类抗生素

氟喹诺酮类抗生素在各种环境基质中积累造成的生态和耐药基因污染等问题已引起广泛的关注。为了能够有效去除环境中氟喹诺酮类抗生素污染并且探究其生物代谢途径,利用嗜热菌Thermus sp. C419在高温(70℃)条件下降解2种典型的氟喹诺酮类抗生素(诺氟沙星和恩诺沙星),分析了菌株C419对这2种药物在单一和混合添加时的降解特性;通过UPLC-MS/MS检测了其相关的降解产物,并推测了可能的代谢途径;利用平板扩散法对生物降解后的氟喹诺酮类药物进行抑菌活性测定。结果表明:氟喹诺酮类化合物可被菌株C419有效降解,降解率为60%～80%;该生物降解过程符合一级动力学模型,培养基中氟喹诺酮类化合物浓度越高,降解率越高,降解半衰期越短;菌株C419对诺氟沙星的生物降解有3条可能的降解途径和7种降解产物,对恩诺沙星的生物降解有4条可能的降解途径和6种降解产物。此外,与2种药物的母体化合物相比,生物降解后药物对不同细菌的抗菌活性均有一定程度的降低,这说明嗜热菌株C419在热环境中去除氟喹诺酮类污染物方面可能会具有良好的实用性和应用前景。     

Removal of aldrin, dieldrin, heptachlor, and heptachlor epoxide using activated carbon and/or Pseudomonas fluorescens free cell cultures

Degradation of aldrin (1,2,3,4,10,10-Hexachloro-1,4,4a,5,8,8a-hexahydro-1,4:5-8-dimethanonaphthalene), heptachlor (1H-1,4,5,6,7,8,8-heptachloro-3a,4,7,7a-tetrahydro-4,7-methano indene), dieldrin (1aalpha,2beta,2aalpha,3beta,6beta,6aalpha,7beta,7aalpha)-3,4,5,6,9,9-Hexachloro-1a,2,2a,3,6,6a,7,7a-octahydro-2,7:3,6-d-methanonaphtha[2,3-b]oxirene, and heptachlor epoxide (1aalpha, 1bbeta,2alpha,5alpha,5alphabeta,6beta,6aalpha-2,3,4,5,6,7,7-Heptachloro-1a,1b,5,5a,6,6a-hexahydro-2,5-methano-2H-inden[1,2-b]-oxirene) was tested using free cultures of Pseudomonas fluorescens under controlled conditions. Pesticide concentrations were monitored by gas chromatography during 120 h. Percentages of degradation and biodegradation rates (BDR) were calculated. Data showed a trend suggesting a relation between chemical structure and degradability. Degradation kinetics for each pesticide tested showed that the highest degradation rates were found in the first 24 h. Kinetics data were adjusted to an empirical equation in order to predict their behavior, and the correlation coefficients obtained were satisfactory. Gas chromatography/mass spectrometry (GC/MS) analysis of the final extracts allowed the identification of chlordene and monodechlorodieldrin, which have been reported as final metabolite produced in the biodegradation of this kind of compounds. Regarding adsorption of pesticides on activated vegetal carbon, we concluded that removal efficiencies between 95.45 and 97.18% can be reached, depending on the pesticide and the carbon dose applied. The values for K from the Freundlich equation were quite similar for the four pesticides (between 1.0001 and 1.04), whereas the n values were quite different for each pesticide in the following order of affinity: dieldrin > aldrin > heptachlor epoxide > heptachlor. Equilibrium times, very important for scaling up the process, were between 43 min and 1 h, for the heptachlor epoxide and the heptachlor, respectively.     

Biodegradation of endosulfan by a soil bacterium

A bacterium capable of metabolizing endosulfan (6,7,8,9,10,10-hexachloro-1,5,5a,6,9,9a-hexahydro-6,9-methano-2,4,3-benzodioxathiepine3-oxide) was isolated from cotton-growing soil and effectively shown to degrade endosulfan into endosulfan sulfate. The bacterium degraded 50% of the compound within 3 days of incubation. Endosulfan sulfate was the only terminal product and no other metabolites were formed during the incubation. Endosulfan and its metabolites were analyzed by gas chromatography. The metabolites formed indicated that the organism follows an oxidative pathway for metabolism of this pesticide. Therefore, the present study, microbial degradation of endosulfan by a soil bacterium, may provide a basis for the development of bioremediation strategies to remediate the pollutants in the environment.     

Biodegradation of Endosulfan by a Soil Bacterium

A bacterium capable of metabolizing endosulfan (6,7,8,9,10,10-hexachloro-1,5,5a,6,9,9a-hexahydro-6,9-methano-2,4,3-benzodioxathiepine3-oxide) was isolated from cotton-growing soil and effectively shown to degrade endosulfan into endosulfan sulfate. The bacterium degraded 50% of the compound within 3 days of incubation. Endosulfan sulfate was the only terminal product and no other metabolites were formed during the incubation. Endosulfan and its metabolites were analyzed by gas chromatography. The metabolites formed indicated that the organism follows an oxidative pathway for metabolism of this pesticide. Therefore, the present study, microbial degradation of endosulfan by a soil bacterium, may provide a basis for the development of bioremediation strategies to remediate the pollutants in the environment.     

Biodegradation of naphthenic acids by rhizosphere microorganisms

Naphthenic acids are components of most petroleums, including those found in the Athabasca Oil Sands of northeastern Alberta. Some naphthenic acids that are solubilized during bitumen extraction from oil sands are acutely toxic to a variety of organisms. Four-month enrichment cultures obtained from the rhizospheres of five plant species native to Alberta, and established with the addition of bitumen (0.5%) as the sole carbon source, revealed a high potential for aerobic degradation of a Merichem commercial preparation of naphthenic acids. Changes in the concentration and composition of the naphthenic acids mixtures during incubation were followed using high-performance liquid chromatography and gas chromatography-electron impact mass spectrometry. Concentrations did not significantly change in the sterile control, but they decreased by up to 90% after 10 days of incubation in the viable cultures. Lower molecular mass naphthenic acids were preferentially degraded, while the proportion of high molecular mass acids increased during incubation. By day 17, the most abundant ions were derived from cellular membranes, corresponding to an increase in microbial numbers in the cultures as naphthenic acids were metabolized. This study is the first to demonstrate the biodegradation potential of microorganisms from rhizosphere soils to biodegrade naphthenic acids.