Biodegradation of lindane (γ-Hexachlorocyclohexane) and other isomers by Bacillus subtilis strain Mz-13i

In this study, the lindane degrading bacterial isolate Mz-13i was isolated using the enrichment culture technique. The isolate was found positive for HCH utilization when screened through col-orimetric assay. It was able to withstand higher concentrations of lindane up to 100 ppm. Fur-ther, the bacterium was cultured on mineral salt medium (MSM) agar plates, and its physiologi-cal, morphological, and biochemical studies and molecular analysis through 16S rRNA sequenc-ing were carried out. The 16S rRNA gene sequence of the isolate was deposited to NCBI GenBank with accession number MF599367 and classified as Bacillus subtilis strain Mz-13i through phylo-genetic analysis. Gas-Chromatography Mass-Spectroscopy (GC-MS) analysis indicated the peaks for pathway-specific metabolites, viz., for gamma-PCCH (7.852), benzoquinone (9.604), benzene car-boxylic acid (12.608), oxalic acid (30.308) and benzene derivatives were found. During degrada-tion, the chloride ions releases such as 0.22 mg/ml (alpha-HCH), 0.27 mg/ml (beta-HCH), 0.48 mg/ml (gamma-HCH), 0.30 mg/ml (delta-HCH). The half-life period calculated was 1.35 days for gamma-HCH and 15.0 days for beta-HCH. From the degradation kinetics data, the gamma-isomer of HCH mediated for degrada-tion, whereas the beta-isomer was hardly degradable. The degradation for four isomers was 58.55% (alpha-HCH), 15% (beta-HCH), 78.25 (gamma-HCH), and 56% (delta-HCH).