Laccase-catalyzed treatment of ketoconazole, identification of biotransformed metabolites, determination of kinetic parameters, and evaluation of micro-toxicity

Ketoconazole is widely used in human and veterinary medicine; however, residual amounts of this antifungal agent have potential adverse effects on ecological health. The present study describes the use of laccase from Trametes versicolor for biotransformation and detoxification of ketoconazole. The substrate was removed at optimum conditions of 45 °C, pH 4.5, incubation time 6 h, ketoconazole concentration 0.3 mg ml−1, 1-hydroxybenzotriazole HBT concentration 1 mM, and laccase activity 1 U ml−1. The use of HBT 1 mM , a laccase mediator, enhanced the yield of elimination. A micro-toxicity study with Pseudokirchneriella subcapitata, Candida albicans, Cryptococcus neoformans, and Saccharomyces cerevisiae showed a decrease in the toxicity of laccase-treated ketoconazole and its isolated metabolites. The kinetic parameters Km and Vmax of laccase-catalyzed removal of the substrate were determined as 0.099 μM and 4.43μmol h−1 mg−1, respecdtively. Two major bioconverted metabolites were also purified and identified.