Biodegradation of pendimethalin by Bacillus circulans

A bacterium capable of degrading herbicide, pendimethalin, was isolated from the contaminated soil by enrichment culture technique and identified as Bacillus circulans. The organism grew on pendimethalin (1 g/L) as the sole source of carbon and accumulated 6-aminopendimethalin and 3,4-dimethyl 2,6-dinitroaniline as metabolites in the culture medium. The cell-free extract of B. circulans grown on pendimethalin contained the activities of pendimethalin nitroreductase and pendimethalin mixed function oxidase. The results suggest that the bacterium degraded pendimethalin by nitroreduction to 6-aminopendimethalin and by oxidative dealkylation to 3,4-dimethyl 2,6-dinitroaniline and pentane, which was utilized as the source of carbon and energy for growth.