Effectual decolorization and detoxification of triphenylmethane dye malachite green (MG) by Pseudomonas aeruginosa NCIM 2074 and its enzyme system

Malachite green (MG) a complex and resonance-stabilized triphenylmethane (TPM) textile dye, resistant to transformation, was decolorized using Pseudomonas aeruginosa NCIM 2074. The bacteria decolorized MG (50 mg l(-1)) completely within 5 h into simple metabolic intermediates in aerobic condition at pH 7 and temperature 35 +/- A 3A degrees C with 53.23% of the COD reduction. Induction in the activities of MG reductase, laccase, and aminopyrine N-demethylase were observed during MG decolorization suggesting these enzymes were involved in the decolorization process. The products after decolorization were examined by UV-Vis, IR spectroscopy, TLC, and HPLC. MG was enzymatically reduced to leucomalachite green (LMG), and further sequential enzymatic reaction converted LMG into N-demethylated and N-oxidized metabolites, including primary and secondary arylamines. The final product formed in this pathway was benzophenone characterized using GC-mass spectroscopy. The cytotoxicity and phytotoxicity study revealed the transformation of MG into non-toxic product by P. aeruginosa NCIM 2074.