Deeb R A, Alvarez-Cohen L
Department of Civil and Environmental Engineering, 631 Davis Hall, MC 1710 University of California at Berkeley, Berkeley, California 94720-1710, USA.
Biotechnol Bioeng. 1999 Mar 5;62(5):526-36.
A microbial consortium derived from a gasoline-contaminated aquifer was enriched on toluene (T) in a chemostat at 20 degrees C and was found to degrade benzene (B), ethylbenzene (E), and xylenes (X). Studies conducted to determine the optimal temperature for microbial activity revealed that cell growth and toluene degradation were maximized at 35 degrees C. A consortium enriched at 35 degrees C exhibited increased degradation rates of benzene, toluene, ethylbenzene, and xylenes in single-substrate experiments; in BTEX mixtures, enhanced benzene, toluene, and xylene degradation rates were observed, but ethylbenzene degradation rates decreased. Substrate degradation patterns over a range of BTEX concentrations (0 to 80 mg/L) for individual aromatics were found to differ significantly from patterns for aromatics in mixtures. Individually, toluene was degraded fastest, followed by benzene, ethylbenzene, and the xylenes. In BTEX mixtures, degradation followed the order of ethylbenzene, toluene, and benzene, with the xylenes degraded last. A pure culture isolated from the 35 degrees C-enriched consortium was identified as Rhodococcus rhodochrous. This culture was shown to degrade each of the BTEX compounds, individually and in mixtures, following the same degradation patterns as the mixed cultures. Additionally, R. rhodochrous was shown to utilize benzene, toluene, and ethylbenzene as primary carbon and energy sources. Studies conducted with the 35 degrees C-enriched consortium and R. rhodochrous to evaluate potential substrate interactions caused by the concurrent presence of multiple BTEX compounds revealed a range of substrate interaction patterns including no interaction, stimulation, competitive inhibition, noncompetitive inhibition, and cometabolism. In the case of the consortium, benzene and toluene degradation rates were slightly enhanced by the presence of o-xylene, whereas the presence of toluene, benzene, or ethylbenzene had a negative effect on xylene degradation rates. Ethylbenzene was shown to be the most potent inhibitor of BTEX degradation by both the mixed and pure cultures. Attempted quantification of these inhibition effects in the case of the consortium suggested a mixture of competitive and noncompetitive inhibition kinetics. Benzene, toluene, and the xylenes had a negligible effect on the biodegradation of ethylbenzene by both cultures. Cometabolism of o-, m-, and p-xylene was shown to be a positive substrate interaction.
从受汽油污染的含水层中获得的微生物群落，在20℃的恒化器中用甲苯（T）进行富集培养，结果发现该群落能够降解苯（B）、乙苯（E）和二甲苯（X）。为确定微生物活性的最佳温度而进行的研究表明，细胞生长和甲苯降解在35℃时达到最大值。在单底物实验中，在35℃下富集的群落对苯、甲苯、乙苯和二甲苯的降解速率有所提高；在苯系物混合物中，观察到苯、甲苯和二甲苯的降解速率提高，但乙苯降解速率下降。发现单个芳烃在一系列苯系物浓度（0至80mg/L）范围内的底物降解模式与混合物中芳烃的模式有显著差异。单独来看，甲苯降解最快，其次是苯、乙苯和二甲苯。在苯系物混合物中，降解顺序为乙苯、甲苯和苯，二甲苯最后降解。从35℃富集的群落中分离出的纯培养物被鉴定为红平红球菌。该培养物在单独和混合状态下对每种苯系物化合物的降解情况，与混合培养物的降解模式相同。此外，红平红球菌能够利用苯、甲苯和乙苯作为主要碳源和能源。用35℃富集的群落和红平红球菌进行的研究，以评估多种苯系物化合物同时存在时潜在的底物相互作用，结果显示出一系列底物相互作用模式，包括无相互作用、促进、竞争性抑制、非竞争性抑制和共代谢。对于群落而言，邻二甲苯的存在使苯和甲苯的降解速率略有提高，而甲苯、苯或乙苯的存在对二甲苯降解速率有负面影响。结果表明，乙苯是混合培养物和纯培养物降解苯系物的最有效抑制剂。对群落中这些抑制作用进行定量分析的尝试表明，存在竞争性和非竞争性抑制动力学的混合情况。苯、甲苯和二甲苯对两种培养物中乙苯生物降解的影响可忽略不计。邻、间、对二甲苯的共代谢表现为一种积极的底物相互作用。
