Simultaneous degradation of cypermethrin and its metabolite, 3-phenoxybenzoic acid, by the cooperation of Bacillus licheniformis B-1 and sphingomonas sp. SC-1.

Abstract

Cypermethrin (CY) and its metabolite, 3-phenoxybenzoic acid (3-PBA), generally coexist in agricultural soil and cause a toxic effect on the human body. In this study, CY and its metabolite 3-PBA were simultaneously degraded by the cooperation of Bacillus licheniformis B-1 and Sphingomonas sp. SC-1. The effects of the inoculation proportion and inoculation method of these two strains, cultivation time, and initial CY content on the degradation of CY and 3-PBA were investigated. Furthermore, the degradation of CY and 3-PBA in soil environment by using the cooperation of these two strains was also determined. When the inoculation proportion of the biomass of strain B-1/strain SC-1 was 3.3:6.7, strain B-1 was inoculated first, and strain SC-1 was inoculated after 24 h of cultivation, 75.60% CY (100 mg L(-1)) was degraded at 72 h and the 3-PBA content was 10.31 mg L(-1). Compared with those by using only strain B-1, the half-life of CY by using these two strains was shortened from 71.90 to 35.71 h, and the yield coefficient of 3-PBA was decreased from 0.8938 to 0.2651. As in the soil environment, the CY content by using these two strains within a period of 25 days declined from 22.71 to 5.33 mg kg(-1) and the 3-PBA content was 1.84 mg kg(-1). Compared with those by using only strain B-1, the half-life of CY by using these two strains was shortened from 19.86 to 11.34 days and the yield coefficient of 3-PBA was decreased from 0.5302 to 0.2056. This work could develop a promising approach for the simultaneous degradation of CY and its metabolite 3-PBA in agricultural soil.