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1.
The degradation of polycyclic aromatic compounds (PACs) has been widely studied. Knowledge of the degradation of PACs by microbial
populations can be utilized in the remediation of contaminated sites. To isolate and identify PAC-degrading bacteria for potential
use in future bioremediation programmes, we established a series of PAC enrichments under the same experimental conditions
from a single sediment sample taken from a highly polluted estuarine site. Enrichment cultures were established using the
pollutants: anthracene, phenanthrene and dibenzothiophene as a sole carbon source. The shift in microbial community structure
on each of these carbon sources was monitored by analysis of a time series of samples from each culture using 16S rRNA polymerase
chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE). Significantly, our findings demonstrate that shifts in
the constituent species within each degradative community are directly attributable to enrichment with different PACs. Subsequently,
we characterized the microorganisms comprising the degradative communities within each enrichment using 16S rRNA sequence
data. Our findings demonstrate that the ability to degrade PACs is present in five divisions of the Proteobacteria and Actinobacteria. By determining the precise identity of the PAC-degrading bacterial species isolated from a single sediment sample, and by
comparing our findings with previously published research, we demonstrate how bacteria with similar PAC degrading capabilities
and 16S rRNA signatures are found in similarly polluted environments in geographically very distant locations, e.g., China,
Italy, Japan and Hawaii. Such a finding suggests that geographical barriers do not limit the distribution of key PAC-degrading
bacteria; this finding is in accordance with the Baas-Becking hypothesis “everything is everywhere; the environment selects”
and may have significant consequences for the global distribution of PAC-degrading bacteria and their use in bioremediation. 相似文献
2.
The stringent new regulations to lower sulfur content in fossil fuels require new economic and efficient methods for desulfurization of recalcitrant organic sulfur. Hydrodesulfurization of such compounds is very costly and requires high operating temperature and pressure. Biodesulfurization is a non-invasive approach that can specifically remove sulfur from refractory hydrocarbons under mild conditions and it can be potentially used in industrial desulfurization. Intensive research has been conducted in microbiology and molecular biology of the competent strains to increase their desulfurization activity; however, even the highest activity obtained is still insufficient to fulfill the industrial requirements. To improve the biodesulfurization efficiency, more work is needed in areas such as increasing specific desulfurization activity, hydrocarbon phase tolerance, sulfur removal at higher temperature, and isolating new strains for desulfurizing a broader range of sulfur compounds. This article comprehensively reviews and discusses key issues, advances and challenges for a competitive biodesulfurization process. 相似文献
3.
The dibenzothiophene (DBT) desulfurization pathway of a facultative thermophilic bacterium Mycobacterium sp. X7B was investigated. Metabolites were identified by gas chromatography-mass spectrometry, and the results showed that 2-hydroxybiphenyl, the end product of the previously reported sulfur-specific pathway (also called 4S pathway), was further converted to 2-methoxybiphenyl. This is the first strain to possess this ability and therefore, an extended 4S pathway was determined. In addition, the DBT-desulfurizing bacterium Mycobacterium sp. X7B was able to grow on DBT derivatives such as 4-methylDBT and 4,6-dimethylDBT. Resting cells could desulfurize diesel oil (total sulfur, 535 ppm) after hydrodesulfurization. GC flame ionization detection and GC atomic emission detection analyses were used to qualitatively evaluate the effect of Mycobacterium sp. X7B treatment on the content of the diesel oil. The total sulfur content of the diesel oil was reduced 86% using resting cell biocatalysts for 24 h at 45 degrees C. 相似文献
4.
Biodesulfurization of dibenzothiophene by growing cells of Gordonia sp. in batch cultures 总被引:1,自引:0,他引:1
A new isolate, identified as Gordonia sp. ZD-7 by 16S rDNA sequence analysis, grew in n-hexadecane containing dibenzothiophene (DBT) which was degraded from 2.8 mM to 0.2 mM within 48 h. Biodesulfurization could be repeatedly performed for more than 190 h, with average desulfurization rates of 5 mmol DBT kg cells (dry wt)−1 h−1. 相似文献
5.
Desulfurization of dibenzothiophene to 2-hydroxybiphenyl by some newly isolated bacterial strains 总被引:7,自引:0,他引:7
Gram-positive, non-spore-forming, non-acid-fast, rod-shaped aerobic bacteria with the ability to desulfurize dibenzothiophene (DBT) or dibenzosulfone (DBTO2) were isolated from soil samples contaminated with fossil fuels. Using a bioavailability method, cells with the desired DbtS+ phenotype were enriched. Modified fluorescence and colorimetric assays were used for the initial detection of 2-hydroxybiphenyl (OH-BP) in microtiter plates; subsequently, isolates were grown in wells of microtiter plates and screened for the production of desulfurization product. Fluorescence under UV light and the production of colored product in the phenol assay were used as presumptive indications of production of OH-BP. Confirmation of the presence of OH-BP was achieved with HPLC, UV-absorbance, and mass spectrometry. Nutrient utilization and fatty acid composition (as discerned with Biolog plates and gas chromatography, respectively) were used to identify presumptively the strains as Rhodococcus erythropolis; colony and cell morphology may not be consistent with the identification achieved by nutrient utilization and fatty acid composition. The desulfurization end product, OH-BP, can not be used as carbon source by the tested strain, N1-36. 相似文献
6.
石油生物脱硫菌Agrobacterium tumefaciens UP-3的固定化研究 总被引:1,自引:0,他引:1
对能降解二苯并噻吩(DBT)的根癌土壤杆菌AgrobacteriumtumefaciensUP3菌株进行了固定化研究,以聚乙烯醇(PVA)和海藻酸钠(SA)混合物为包埋法固定化载体,固定化最佳操作条件为4℃交联,PVA和SA混合物总浓度7%,两者最佳浓度比为6,细胞浓度为0.05g/mL。当DBT加入量为2.7mmol/L时,UP-3的静息细胞最高脱硫率为13%,而固定化细胞的脱硫效率超过了60%;固定化细胞的最佳使用条件为降解5d,温度28℃~32℃。 相似文献
7.
8.
The resting cells of a new isolate of Rhodococcus erythropolis FSD-2 were used to desulfurize diesel fuels. About 97% of the total sulfur content in the hydrodesulfurized diesel was removed
by the two consecutive biodesulfurization (BDS) processes with the majority (∼94%) being removed in the first treatment, resulting
in diesel with a sulfur content of 5.7 μg ml−1. 相似文献
9.
Elizabet Aranda Matthias Kinne Martin Kluge René Ullrich Martin Hofrichter 《Applied microbiology and biotechnology》2009,82(6):1057-1066
The conversion of the heterocycle dibenzothiophene (DBT) by the agaric basidiomycetes Agrocybe aegerita and Coprinellus radians was studied in vivo and in vitro with whole cells and with purified extracellular peroxygenases, respectively. A. aegerita oxidized DBT (110 μM) by 100% within 16 days into eight different metabolites. Among the latter were mainly S-oxidation products (DBT sulfoxide, DBT sulfone) and in lower amounts, ring-hydroxylation compounds (e.g., 2-hydroxy-DBT).
C. radians converted about 60% of DBT into DBT sulfoxide and DBT sulfone as the sole metabolites. In vitro tests with purified peroxygenases
were performed to compare the product pattern with the metabolites formed in vivo. Using ascorbic acid as radical scavenger,
a total of 19 and seven oxygenation products were detected after DBT conversion by the peroxygenases of A. aegerita (AaP) and C. radians (CrP), respectively. Whereas ring hydroxylation was favored over S-oxidation by AaP (again 2-hydroxy-DBT was identified), CrP formed DBT sulfoxide as major product. This finding suggests that
fungal peroxygenases can considerably differ in their catalytic properties. Using H2
18O2, the origin of oxygen was proved to be the peroxide. Based on these results, we propose that extracellular peroxygenases
may be involved in the oxidation of heterocycles by fungi also under natural conditions. 相似文献
10.
Yu-Guang Li Hong-Shuai GaoWang-Liang Li Jian-Min Xing Hui-Zhou Liu 《Bioresource technology》2009,100(21):5092-5096
In situ cell separation and immobilization of bacterial cells for biodesulfurization were developed by using superparamagnetic Fe3O4 nanoparticles (NPs). The Fe3O4 NPs were synthesized by coprecipitation followed by modification with ammonium oleate. The surface-modified NPs were monodispersed and the particle size was about 13 nm with 50.8 emu/g saturation magnetization. After adding the magnetic fluids to the culture broth, Rhodococcus erythropolis LSSE8-1 cells were immobilized by adsorption and then separated with an externally magnetic field. The maximum amount of cell mass adsorbed was about 530 g dry cell weight/g particles to LSSE8-1 cells. Analysis showed that the nanoparticles were strongly absorbed to the surface and coated the cells. Compared to free cells, the coated cells not only had the same desulfurizing activity but could also be easily separated from fermentation broth by magnetic force. Based on the adsorption isotherms and Zeta potential analysis, it was believed that oleate-modified Fe3O4 NPs adsorbed bacterial cells mainly because of the nano-size effect and hydrophobic interaction. 相似文献