Characterization of Cyclohexane and Hexane Degradation by Rhodococcus SP. EC1

摘要

Cyclohexane is a recalcitrant compound that is more difficult to degrade than even n-alkanes or monoaromatic hydrocarbons. In this study, a cyclohexane-de-grading consortium was obtained from oil-contaminated soil by an enrichment culture method. Based on a 16S rDNA PCR-DGGE (denaturing gradient gel electrophoresis) method, this consortium was identified as comprising alpha-proteobacteria, action-bacteria, and gamma-proteobacteria. One of these organisms, Rhodococcus sp. Ecl, was isolated and shown to have excellent cyclohexane-degrading ability. The maximum specific cyclohexane degradation rate (V_(max)) for EC1 was 246.4 μmolg-DCW~(-1) (dry cell weight) h~(-1). In addition to its cyclohexane degradation abilities, EC1 was also able to strongly degrade hexane, with a maximum specific hexane degradation rate of 361 μmol·g-DCW~(-1)·h~(-1). Experiments using ~(14)C-hexane revealed that EC1 mineralized 40.3% of hexane into CO_2 and converted 52.8% into biomass. Moreover, EC1 could use other hydrocarbons, including methanol, ethanol, acetone, methyl tert-butyl ether (MTBE), pyrene, diesel, lubricant oil, benzene, toluene, ethylbenzene, m-xylene, p-xylene and o-xylene. These findings collectively suggest that EC1 may be a useful biological resource for removal of cyclohexane, hexane, and other recalcitrant hydrocarbons.