Decolorization and biodegradation of triphenylmethane dye,brilliant green,by Aspergillus sp. isolated from Ladakh,India

Brilliant green, used extensively to color silk and wool in the commercial textile industry is a hazardous recalcitrant. Aspergillus sp. strain CB-TKL-1 isolated from a water sample from Tsumoriri Lake, Karzok, Ladakh, India, was found to completely decolorize this dye within 72 h when cultured under aerobic conditions at 25 °C. The extent of decolorization was monitored by the decrease in absorbance maxima of the dye by UV–visible spectroscopy. The decolorization was optimum at pH 5 and 35 °C when agitated at 200 rpm. Addition of glucose (2%) as a carbon source and sodium nitrate (0.2%) as a nitrogen source enhanced the decolorization ability of the culture. The culture exhibited maximum extent of decolorization of brilliant green with a C:N ratio of 2.5 after 72 h. Thirteen N-demethylated decolorized products of brilliant green were identified based on UV–visible spectroscopy, Fourier Transform Infrared (FT-IR) spectroscopy and liquid chromatography–electrospray ionization mass spectrometry (LC–ESI-MS) analysis at the end of 72 h before mineralization. The difference of the relative absorption peaks in the decolorized sample indicated a linear release of N-demethylated compounds, indicating a stepwise N-demethylation in the decolorization process.