Enhancement of cypermethrin degradation by a coculture of Bacillus cereus ZH-3 and Streptomyces aureus HP-S-01

Degradation of cypermethrin was significantly enhanced in a coculture of Bacillus cereus ZH-3 and Streptomyces aureus HP-S-01. In the pure culture, longer half-lives (t(1/2) = 32.6-43.0 h) of cypermethrin were observed, as compared to the mixed cocultures (t(1/2)= 13.0 h). The optimal degradation conditions were determined to be 28.2 degrees C and pH 7.5 based on response surface methodology (RSM). Under these conditions, the mixed cultures completely metabolized cypermethrin (50 mg L-1) within 72 h. Analysis of degradation products of cypermethrin indicated that the microbial consortium converted cypermethrin to alpha-hydroxy-3-phenoxy-benzeneacetonitrile, 3-phenoxybenzaldehyde and 4-phenoxyphenyl-2,2-dimethyl-propiophenone, and subsequently transformed these compounds with a maximum specific degradation rate (q(max)), half-saturation constant (K-s) and inhibition constant (K-i) of 0.1051 h(-1), 31.2289 mg L-1 and 220.5752 mg L-1, respectively. This is the first report of a proposed pathway of degradation of cypermethrin by hydrolysis of ester linkage and oxidization of 3-phenoxybenzyl in a coculture. Finally, this coculture is the first described mixed microbial consortium capable of metabolizing cypermethrin. (C) 2012 Elsevier Ltd. All rights reserved.