Yeast Yeast 2006; 23: 315–323. Published online in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/yea.1356 Research Article Biotransformation of malachite green by Saccharomyces cerevisiae MTCC 463 J. P. Jadhav and S. P. Govindwar* Department of Biochemistry, Shivaji University, Kolhapur 416 004, India *Correspondence to: S. P. Govindwar, Department of Biochemistry, Shivaji University, Kolhapur 416 004, Maharashtra, India. E-mail: spgovindwar@rediffmail.com Received: 13 September 2005 Accepted: 17 January 2006 Abstract In recent years, use of microbial biomass for decolourization of textile industry wastewater is becoming a promising alternative in which some bacteria and fungi are used to replace present treatment processes. Saccharomyces cerevisiae MTCC 463 decolourized the triphenylmethane dyes (malachite green, cotton blue, methyl violet and crystal violet) by biosorption, showing different decolourization patterns. However, malachite green decolourized by biosorption at the initial stage and further biodegradation occurred, about 85% in plain distilled water within 7 h, and about 95.5% in 5% glucose medium within 4 h, under aerobic conditions and at room temperature. Decolourization of malachite green depends on various conditions, such as concentration of dye, concentration of cells, composition of medium and agitation. HPLC, UV-VIS, FTIR and TLC analysis of samples extracted with ethyl acetate from decolourized culture flasks confirmed the biodegradation of malachite green into several metabolites. A study of the enzymes responsible for the biodegradation of malachite green in the control and cells obtained after decolourization showed the activities of laccase, lignin peroxidase, NADH-DCIP reductase, malachite green reductase and aminopyrine N-demethylase in control cells. A significant increase in the activities of NADH-DCIP reductase and MG reductase was observed in the cells obtained after decolourization, indicating a major involvement of reductases in malachite green degradation. Copyright  2006 John Wiley & Sons, Ltd. Keywords: Saccharomyces cerevisiae ; malachite green; biotransformation; leucoma- lachite green; biosorption; biodegradation; yeast; MG reductase Introduction A major class of synthetic dyes includes the azo, anthroquinone and triphenylmethane dyes. Approx- imately 10 000 different dyes and pigments are used industrially and over 0.7 million tonnes of synthetic dyes are produced annually worldwide. These dyes have also been found in soil and river sediments as a consequence of improper chemical disposal, leading to reduction of sunlight penetra- tion, which in turn decreases both photosynthetic activity and dissolution of oxygen concentration (Nelson and Hites, 1980). Of these dyes, triphenylmethane dyes are used extensively in textile industries for dying cotton, wool, silk, nylon, etc. (Culp and Beland, 1996). Malachite green, an N-methylated diaminotri- phenylmethane dye, is used as the most efficient antifungal agent in the fish farming industry (Schnick, 1988). Therefore, potential human expo- sure to malachite green occurs due to the con- sumption of treated fish and by workers in the dye and aquaculture industry (Alderman and Clifton- Hadley, 1993). Malachite green is highly toxic to human beings, as it affects the immune and repro- ductive systems and possesses carcinogenic prop- erties (Fernandes et al., 1991). Even though the use of this dye has been banned in several countries and is not approved by the US Food and Drug Admin- istration, it is still used due to its low cost, ready availability and efficacy (Schnick, 1988). For the removal of dyes from wastewater efflu- ent there are several decolourization methods, such as adsorption, chemical precipitation, photolysis, Copyright  2006 John Wiley & Sons, Ltd.