Rhodococcus sp. ML-0004, a novel strain for producing epoxide hydrolase, was isolated from soil in this study. The epoxide hydrolase can catalyze the stereo-specific hydrolysis of cis-epoxysuccinic acid to generate L(+)-tartaric acid. By examining physiological, biochemical characteristics and comparing its 16S rDNA gene sequence, it was identified as Rhodococcus opacus, and named R. opacus ML-0004. The optimal conditions for epoxide hydrolase production from R. opacus ML-0004 were also investigated. Propanediol and (NH4)(2)SO4 were selected as carbon source and nitrogen source, respectively, for the production of R. opacus ML-0004 epoxide hydrolase. The optimal conditions for epoxide hydrolase production were fermentation temperature = 28 degrees C, pH 7.0, and cultivation time = 26 h. Under these conditions, the maximum epoxide hydrolase activity reached 10.5 U mL(-1). (C) 2007 Elsevier Ltd. All rights reserved.