Transformation of triclosan by a novel cold-adapted laccase from Botrytis sp. FQ

This work investigated the transformation of triclosan (TCS) by the laccase produced by a pathogen isolated from rotten tomato. The pathogen was characterized as Botrytis sp. FQ, belonging to subphylum Deuteromycotina . The laccase exhibited cold-adaptation with relatively high activity at 20°C. The laccase could effectively transform TCS. Approximately 62% TCS could be removed at dose of 1.0 unit∙mL –1 in 120 min. The reaction rate appeared to be pseudo-first-order to the concentration of the substrate, suggesting the laccase activity remained stable during the reaction. Transformation products of TCS were analyzed by mass spectrometry and it was revealed that TCS dimers were formed via radical coupling pathways. During this process, laccase catalyzed oxidation of TCS to form a radical intermediate is the rate limiting step. However, this step can be reversed by humic acid. Overall, the laccase showed great potential in the treatment of phenolic contaminants. Since laccase is widely presented in natural environment, this study also revealed an important pathway involved in the transformation of phenolic contaminants in the environment.