Comparative study on crude and partially purified laccase from Polyporus durus ATCC 26726 in the decolorization of textile dyes and wastewater treatment

Abstract

Background and objective In textile processing, 50% of the dye is released as effluent which is considered as hazardous contaminant that threats environment and human life. The use of laccase enzyme for dye decolorization is cost effective and environmentally friendly. So, the main objective of the present study is the production of microbial laccase with high yield using low-cost substrates. The study also involved comparing and evaluating the dye decolorization efficiency of both crude and partially purified laccase enzymes. Materials and methods Six fungal strains were tested for laccase productivity. Some agro-industrial wastes were evaluated for laccase production by the most potent fungus. The produced laccase was partially purified by acetone precipitation. Both the crude and the partially purified laccase were evaluated for decolorization of some textile dyes and two synthetic wastewater solutions. Results and conclusion The fungus Polyporus durus ATCC 26726 exhibited the highest laccase productivity among all the tested fungi. Maximal enzyme productivity (2297 U/ml) was reached after 7 days by submerged fermentation using a medium containing 60 g/l wheat bran with the addition of 1 mmol/l copper on the fifth day of fermentation. The produced laccase was partially purified by 40% acetone concentration with an 8.1-fold purification factor. Both the crude and the partially purified laccase exhibited high efficiency to decolorize reactive blue 19, acid blue 225, and reactive violet 5 dyes. The crude enzyme exhibited 100 and 96.4% decolorization activities against the synthetic wastewater solutions A and B, respectively. However, the decolorization activity of the partially purified enzyme was 100% against both solutions A and B. Hence laccase enzyme from P. durus ATCC 26726 could be used effectively for the removal of textile dye pollutants in both its crude and partially purified form without the need to redox mediators.