ABSTRACT
Brevibacillus laterosporus MTCC 2298 was screened for the decolorization of eight triphenylmethane dyes. Decolorization of malachite green was found to be fastest (87% within 3 hours, at the concentration 0.1 g/L) among the screened dyes. Various triphenylmethane dyes showed differential induction patterns of the dye-degrading enzymes. The activities of the laccase, nicotinamide adenine dinucleotide-dichlorophenolindophenol reductase (NADH-DCIP reductase), malachite green reductase, and aminopyrine N-demethylase were increased in the cell-free extract obtained after decolorization of malachite green. Fourier transform infrared spectral analysis indicated formation of N-demethylated products, including primary and secondary aryl amines. High-performance liquid chromatography analysis confirmed the transformation of malachite green into new metabolites rather than its reduced form, leucomalachite green. Gas chromatography-mass spectroscopy analysis detected new degradation products, such as reduced tetradesmethyl leucomalachite green (m/z 283) and [4-(1-cyclohexyl)-(1'-phenyl)-methyl]-2, 4-hexenoic acid (m/z 282). Complete decolorization of malachite green also was observed by the partially purified laccase from B. laterosporus.
