Decolourisation of Crystal Violet and Malachite Green By Fungi

Abstract

Decolourisation of crystal violet and malachite green by white rot fungi, Polyporus elegans, Trametes versicolor, Lenzites betulina and soil fungus Mucor mucedo isolated from dye effluent amended soils was studied. There was no toxic effect of crystal violet on the growth of the four fungi but malachite green showed retardation of growth. Mucor mucedo decolourised 78% of the crystal violet and 65% of malachite green. The white rot fungi showed more than 60% decolourisation of crystal violet and 26 to 57% decolourisation of malachite green. In the process of decolourisation, lignin peroxidase production was high at 15 days incubation by all the organisms. Manganese peroxidase was secreted more after 10 days of incubation and laccase production was high after 15 days of incubation by Polyporus elegans and Trametes versicolor and after 10 days in the case of Lengites betulina. Mucor mucedo failed to secrete manganese peroxidase and laccase in all its incubations. INTRODUCTION: The textile industries utilize large volumes of water in its processing operations and generate substantial quantities of wastewater (Hutton, 1972). Dye wastes are usually discarded into water with or without processing. Aesthetic merit, gas solubility and water transparencies are affected by the presence of dyes even in small amounts. The presence of colour in waste water is very important and usually contributes the major fraction of biochemical oxygen demand. Among many classes of synthetic dyes used in the textile and dyeing industries, triphenyl methane group of dyes such as crystal violet and malachite green are the largest and most versatile and play a predominant role in almost every type of application (Bumpus & Brock, 1988). Crystal violet (N, N, N 1 , N 1 , N 11 , N 11 -hexa-methyl-para-rosaniline) has been extensively used in human and veterinary medicine as a biological stain and as a textile dye (Bangert et al., 1977; Eiichi et al., 1985). Some triphenyl methane dyes have been shown to be carcinogenic especially crystal violet which has been proved to be potent carcinogen (Au et al., 1978). Malachite green is not approved by the US Food and Drug Administration and has nominated it to be a priority chemical for carcinogenic testing by the National Toxicology Program in 1993.