Biodegradation of Butachlor by Bacillus altitudinis and Identification of Metabolites
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Biodegradation of Butachlor by Bacillus altitudinis and Identification of Metabolites Ravneet Kaur1 · Dinesh Goyal1 Received: 7 January 2020 / Accepted: 14 May 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
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 41KF2bT 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 (t1/2) 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.
Introduction Butachlor (N-(butoxymethyl)-2-chloro-N-(2,6-diethylphenyl)acetamide), commonly known as machete, is a chloroacetamide compound extensively used as a pre-emergence or early post-emergence herbicide for controlling unwanted annual grass, certain broadleaved weeds and underwater macrophytes found in freshwater and fish water bodies [1, 2]. It is a selective and systemic herbicide which acts by inhibiting the enzymes responsible for geranylgeranyl pyrophosphate cyclization and elongation of the long-chain fatty acids [2]. It has become a very popular herbicide across Asia with a utilization rate of about 4.5 × 107 kg per year [3, 4] at a recommended field dosage of 3000 mL ha−1 [5]. India accounts for approximately 6.75 × 106 kg of annual usage of butachlor [6]. Butachlor has a half-life of 1.6 days to 29 days in soil [7]. Persistence of butachlor in the environment due to its indiscriminate application has led to several health and * Dinesh Goyal [email protected] 1
environmental complications [8]. It is suspected to be carcinogenic in nature, known to induce malignant transformation in vitro by stimulating cell proliferation, mitochondrial dysfunction, chromosomal breakage, oxidative DNA damage [9] and disrupting endocrine system [10]. Several reports suggest butachlor to be a neurotoxin [11] and growth retardant in earthworms [12]. Due to these adverse effects, its removal from soil and water becomes necessary. Although various chemical and physical processes
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