BTEX degradation by a newly isolated bacterium: Performance, kinetics, and mechanism

A new isolate identified as Rhodococcus sp. ZJUT312 via taxonomic and 16S rRNA analysis was used for the efficient degradation of benzene, toluene, ethylbenzene, and xylene (BTEX). The strain ZJUT312 was able to degrade all the BTEX. Their average biodegradation rates followed the order o-xylene > ethylbenzene > toluene > benzene > m-xylene > p-xylene. The degradation rate of o-xylene reached as high as 0.117 mmol L-1 h(-1), which was one to two orders of magnitude higher than that of all other reported o-xylene degrading bacteria. GC-MS analysis revealed that o-xylene degradation pathway mainly proceeded with 2-methylbenzylalcohol as an intermediate and CO2 as a final product. Mass balance analysis of the carbon element indicated that approximately 59% the o-xylene carbons were transferred to cell biomass and about 20% were mineralized into CO2. Furthermore, the o-xylene degradation kinetics fitted well with Haldane's model. The maximum specific degradation rate (0.953 h(-1)) was approximately 2.25 times higher than the reported data in the literature.