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 ± 3°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.