Biodegradation of Acetochlor and 2-methyl-6-ethylaniline by Bacillus subtilis and Pseudomonasfluorescens

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Two bacterial strains, Pseudomonas fluorescens KT3 and Bacillus subtilis 2M6E, isolated from soil utilized acetochlor and 2-methyl-6-ethylaniline (2M6E) as carbon and nitrogen sources, respectively. The strain mixture utilized more than 95% acetochlor within 30 h and nearly 100% 2M6E within 24 h from each initial concentration of 100 mg/L. Although B. subtilis 2M6E could not degrade acetochlor, the strain augmented the degradation rate mediated by P. fluorescens KT3. In its degradation process, KT3 converted acetochlor to 2M6E as an intermediate product. Moreover, Bacillus subtilis 2M6E transformed 2M6E into catechol. The enzyme activities involved in the degradation pathways indicated that both strains transformed the chemicals via an ortho-cleavage pathway. The formation of dual-species biofilms and their participation in biodegradation were also investigated. The obtained results showed that the combination of these strains augmented their biofilm-forming capabilities and enhanced the degradation rates of both acetochlor and 2M6E. This study exemplifies the efficient use of mixed cultures of both suspended and biofilm cells in degrading acetochlor and 2M6E.