Kinetics of degradation of carbendazim by B. subtilis strains: possibility of in situ detoxification.

Abstract

Food safety is a global concern due to the increased use of pesticides in agriculture. In grapes, carbendazim is one of the frequently detected fungicides. However, it is amenable to biodegradation. In this study, we aimed to assess the degradation of carbendazim by four Bacillus subtilis strains, which had earlier shown potential for biocontrol of grape diseases. In liquid medium, each of the four strains, namely, DR-39, CS-126, TL-171, and TS-204, could utilize carbendazim as the sole carbon source. The half-life was minimized from 8.4days in the uninoculated spiked control to 4.0-6.2days by the four strains. In Thompson Seedless sprayed with carbendazim at 1.0gL(-1), the residue on grape berries in control was 0.44mgkg(-1) after 25days of application, whereas in grapes treated with the four B. subtilis strains, the residues had decreased to 0.02mgkg(-1). The degradation kinetics showed low half-lives of 3.1 to 5.2days in treated grapes as compared to 8.8days in control. In inoculated soils, the half-lives were 5.9 to 7.6days in autoclaved and 6.5 to 7.2days in nonautoclaved soils as compared to 8.2 and 8.0days in respective controls. The growth dynamics of these strains in all the three matrices was not affected by presence of carbendazim. Bacillus strains TS-204 and TL-171 showed higher degradation rate than the other two strains in all the three matrices and show promise for in situ biodegradation of carbendazim.