Optimization of growth media for enhanced production of laccase by Cryptococcus albidus and its application for bioremediation of chemicals

Cryptococcus albidus, isolated from the sediments of Century Pulp and Paper Mill, Lalkuan, Nainital, Uttarakhand, India, produced a copper containing oxidase, laccase, that was capable of degrading environmental pollutants. Bagasse was the most efficient inducer for laccase production. The Taguchi approach was used to optimize the growth media for five factors, i.e., pH, copper sulphate, carbon, nitrogen, and the inducer at four levels using an M-16 orthogonal array. The optimum conditions for laccase production were pH (6), CuSO₄ (2  mmol/L), meat peptone (0·5%), glucose (0·1%), and bagasse (1·0%). After optimization, laccase production increased seven times from 32 to 219  IU/mg. The inducer (bagasse) had maximum effect on laccase production leading to 52% increase, while pH had minimum effect with 7% increase. Growth media with laccase activity (2 U/mL) was applied for the bioremediation of dyes, effluent, and chemical compounds. These experiments showed that the growth media with laccase activity (2 U/mL) produced by Cryptococcus albidus had good potential for bioremediation of toxic and recalcitrant compounds. Further, the laccase enzyme extracted from the growth media was fractionated by DEAE-cellulose ion-exchange chromatography, and the molecular weight of the enzyme determined by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS  –  PAGE) was found to be 64  kDa. The activity of laccase was confirmed by native PAGE, in which ABTS was used for staining gel.