Effects of Two Surfactants and Beta-Cyclodextrin on Beta-Cypermethrin Degradation by Bacillus licheniformis B-1

The biodegradation efficiency of beta-cypermethrin (beta-CY) is low especially at high concentrations mainly due to poor contact between this hydrophobic pesticide and microbial cells. In this study, the effects of two biodegradable surfactants (Tween-80 and Brij-35) and beta-cydodextrin (beta-CD) on the growth and cell surface hydrophobicity (CSH) of Bacillus licheniformis B-1 were studied. Furthermore, their effects on the solubility, biosorption, and degradation of beta-CY were investigated. The results showed that Tween-80 could slightly promote the growth of the strain while Brij-35 and beta-CD exhibited little effect on its growth. The CSH of strain B-1 and the solubility of beta-CY were obviously changed by using Tween-80 and Brij-35. The surfactants and beta-CD could enhance beta-CY biosorption and degradation by the strain, and the highest degradation was obtained in the presence of Brij-35. When the surfactant or beta-CD concentration was 2.4 g/L, the degradation rate of beta-CY in Brij-35, Tween-80, and beta-CD treatments was 89.4%, 50.5%, and 48.1%, respectively. The half-life of beta-CY by using Brij-35 was shortened by 69.1 h. Beta-CY content in the soil with both strain B-1 and Brij-35 decreased from 22.29 mg/kg to 4.41 mg/kg after incubation for 22 d. This work can provide a promising approach for the efficient degradation of pyrethroid pesticides by microorganisms.