Biodegradation of pretilachlor and butachlor by novel bacterial strains isolated from paddy field soil

In this study, two pretilachlor-degrading bacterial strains isolated from soil, Enterobacter sp. Pre1 and Pseudomonas sp. Pre2 completely utilized the compound as a sole carbon, energy and nitrogen source under aerobic conditions. The determination of degradation kinetics revealed that the rates of both isolates followed the Michaelis-Menten model, in which the maximum utilization rates of Enterobacter sp. Pre1 and Pseudomonas sp. Pre2 were 0.010 ± 0.0012 and 0.0060 ± 0.0007 mM/h, respectively. Moreover, Pseudomonas sp. Pre2 exhibited effective degradation of butachlor. Enterobacter sp. Pre1 showed better biofilm formation than the later one. Their immobilized biomass in polyurethane foam (PUF) reached 323.4 ± 35.6 mg/g PUF completely degrading pretilachlor at 0.15 mM within 12 h in a packed bed bioreactor. A metabolite, 2,6-diethylaniline, was produced during the degradation by both strains. Besides, 4-amino-3,5-diethyl phenol and aniline were the metabolites in the degradation by Enterobacter sp. Pre1 and Pseudomonas sp. Pre2, respectively. This study confirmed the efficiency and mechanisms in the degradation of pretilachlor by freely suspended and immobilized cells of the isolated bacteria.