Substrate interactions during biodegradation of benzene/alkylbenzene mixtures by Rhodococcus sp. ustb-1

Abstract

In this study, the toxicity effects of benzene (B), toluene (T), ethylbenzene (E), xylene (X) alone and substrate interactions in binary mixtures of BT, BE and BX mixed with equal mass concentrations on facultative anaerobic Rhodococcus sp. ustb-1 in LB medium were examined by a microcalorimetric method. The results showed that T, E and X alone aren't severely toxic to strain ustb-1 when the concentrations reach 800 μg mg−1, but B alone and these binary mixtures exhibit obvious inhibitory effects on the growth of ustb-1 at the dose of 100 μg mg−1. The toxicity of B in the presence of T and X is not significantly different from B alone, but E increased the toxicity of B. In mineral salt medium, all T and X were removed within 72 h, while complete degradation of B and E did not occur during biodegradation of these binary mixtures. The degradation of B was stimulated in the presence of T and X, but it was inhibited by E. The decreased degradation of B in BE, compared with the degradation of B alone, was attributed to an increase in the toxicity of B in the presence of E.