title: Characterization of cyclohexane and hexane degradation by Rhodococcus sp. EC1.
abstract: Cyclohexane is a recalcitrant compound that is more difficult to degrade than even n-alkanes or monoaromatic hydrocarbons. In this study, a cyclohexane-degrading consortium was obtained from oil-contaminated soil by an enrichment culture method. Based on a 16S rDNA polymerase chain reaction-denaturing gradient gel electrophoresis method, this consortium was identified as comprising Alpha-proteobacteria, Actinobacteria, and Gamma-proteobacteria. One of these organisms, Rhodococcus sp. EC1, was isolated and shown to have excellent cyclohexane-degrading ability. The maximum specific cyclohexane degradation rate (Vmax) for EC1 was 246 micromol g-DCW(-1) (dry cell weight)h(-1). The optimum conditions of cyclohexane degradation were 25-35 degrees C and pH 6-8. In addition to its cyclohexane degradation abilities, EC1 was also able to strongly degrade hexane, with a maximum specific hexane degradation rate of 361 micromol g-DCW(-1)h(-1). Experiments using 14C-hexane revealed that EC1 mineralized 40% of hexane into CO2 and converted 53% into biomass. Moreover, EC1 could use other hydrocarbons, including methanol, ethanol, acetone, methyl tert-butyl ether, 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.
authors.affiliation: Department of Environmental Science and Engineering, Ewha Womans University, 11-1, Daehyun-dong, Seodaemun-Gu, Seoul 120-750, Republic of Korea.
authors.forename: Eun-Hee
authors.initials: EH
authors.lastname: Lee
authors.forename: Kyung-Suk
authors.initials: KS
authors.lastname: Cho
mesh_terms: D003510:Cyclohexanes / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D006586:Hexanes / Q000378:metabolism*; D016133:Polymerase Chain Reaction; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D012240:Rhodococcus / Q000235:genetics / Q000378:metabolism*; D012988:Soil Microbiology; D012989:Soil Pollutants / Q000378:metabolism*
chemical_list: D003510:Cyclohexanes; D006586:Hexanes; D012336:RNA, Ribosomal, 16S; D012989:Soil Pollutants; C506365:Cyclohexane