Biodegradation of Butachlor by Bacillus altitudinis and Identification of Metabolites

Abstract

Butachlor is a chloroacetamide pre-emergence herbicide, with a half-life of 1.6 to 29 days. It is a suspected carcinogen, genotoxin, neurotoxin and persists in the environment having toxic effect on living systems. Butachlor degrading bacterial strain A16 was isolated from coal tar contaminated soil, which showed 99.38% similarity with Bacillus altitudinis 41KF2b^T as revealed by 16S rRNA analysis. B. altitudinis strain A16 utilised butachlor as a sole source of carbon and degraded 90% of 50 mg L⁻¹ butachlor in 5 days at a rate constant and half-life (t_1/2) of 0.02 h⁻¹ and 34.65 h, respectively, following the first-order reaction kinetics. Five metabolites (N-(butoxymethyl)-N-(2-chloroethyl)-2,6-diethylaniline, (N-(butoxymethyl)-2-chloro-N-(2-ethylphenyl) acetamide, N-(butoxymethyl)-2,6-diethyl-N-propylaniline, 2-chloro-N-(2,6-diethylphenyl) acetamide and 2,6-diethylaniline) were produced during the breakdown of butachlor by B. altitudinis A16 as identified by GC–MS analysis, which are further mineralized to carbon dioxide and water. A metabolic pathway is proposed and compared with other bacteria. The findings have immense beneficial application since such microbes can be used on large scale for faster soil bioremediation and minimizing negative impact of pesticide butachlor on health and environment.