| Summary: | 碩士 === 嘉南藥理科技大學 === 環境工程與科學系暨研究所 === 99 === PAHs are aromatic hydrocarbons with two or more fused benzene rings. These compounds enter into the environment via many ways including incomplete combustion of fossil fuels, waste incineration, as well as accidental spilling of hydracarbons. PAHs are hydraphobic pollutants highly persistent in soil environment. Their persistence increase with increase in the molecular weight. The environmental fate of PAHs is of concern cause of their mutagenicity, ecotoxicity, and carcinogenic potential of high molecular weight PAHs. The remediation technologies for PAH-contaminated soils include solvent extraction, bioremediation, phytoremediation, chemical oxidation, thermal treatment. Pyrene, a four-ring PAH with structural similarity to several carcinogenic PAHs, is a widespread pollutant in the soil environment, and, it is one of the most predominant PAH in the environment. Bioremediation is the tool to transform pyrene to less/non harzardous forms with less input of chemicals and energy. Thus, a deeper understanding of the pyrene biodegradation will facilitate better ways to remediate pyrene pollution.
In this study, the pyrene degraders are isolated from the sludge samples from various disposing sties of petroleum stations and factories in southern Taiwan and enrichment was carried out with 100 mgL-1 pyrene as a sole carbon and energy source in a mineral medium. The tolerance of pyrene by the isolates was investigated to select the effective pyrene degraders. The 16S rDNA sequence of H1, L1 and N1 had 99% indentity to Bacillus cereus and Bacillus thuringiensis strains. R1 stain best matched to Escherichia coli (96% indentity). W1 might be closely related to Bacillus megaterium (98% indentity), and FA was similar with Klebsiella pneumoniae (99% indentity).
The biodegradation assay of pyrene, effect of cometabolism and surfactants (Tween80 and TritonX-100) were also discussed in aqueous media inoculation with isolted strains, respectively. The higher growth rate of test strains was obtained when Tween80 was used as surfactant instead of TritonX-100. W1 and N1 could carry out efficient degradation of pyrene as a carbon and energy source in mineral medium. All strains degrade pyrene more efficient when it co-metabolized with low concentration of glucose. N1 and W1 strains showed the higher degradation activity to mineralize 100 mg kg-1 pyrene in sandy alluvial soil. In addition, the degradtion of pyrene in soil suggested the potential application of two islates (W1 and N1) with adding co-metabolism substrates (1g kg-1 soil) in bioremediation.
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