Biotransformation of 4, 4'-dihydroxybiphenyl and dienestrol by laccase from Trametes versicolor

Abstract

Disemboguing of industrial and household wastes into the environment create significant challenge to human health. Both 4,4′–dihydroxybiphenyl and dienestrol are a type of environmental micro-pollutants that dreadfully act as endocrine disruptors to both humans and wildlife. In the current study, laccase from Trametes versicolor was exploited for the biotransformation of 4,4′–dihydroxybiphenyl and dienestrol. Although both the micro-contaminants possess two phenolic moieties in their structures, laccase oxidizes 4,4′–dihydroxybiphenyl with significantly higher efficiency than dienestrol. Immobilization of laccase viz., encapsulation in polyacrylamide gel (PAG-laccase) and construction of cross-linked enzyme aggregates (CLEA-laccase) led to a decrease in turnover number, and substrate affinity, which consequently resulted in a reduced catalytic activity. However, immobilization of laccase conferred substantial stability compared to free enzyme. Immobilized laccase exhibited greater thermal stability with a wider activity range of pH and temperature. Encapsulation of laccase also considerably increased its capability to withstand higher concentrations of salt, organic solvents and inhibitors than its free form. Unlike free laccase, encapsulated laccase acquired the attribute of reusability in multiple catalytic reactions, which enormously compensated its reduced activity and enhanced its applicability than native form. This study comprehensively delineates the catalytic properties of native and immobilized laccase in the removal of noxious endocrine disruptors like 4,4′–dihydroxybiphenyl and dienestrol.