Characterization of a novel laccase from the isolated Coltricia perennis and its application to detoxification of biomass

A highly efficient laccase-producing fungus was isolated from soil and identified as Coltricia perennis SKU0322 by its morphology and by comparison of its internal transcribed spacer (ITS) rDNA gene sequence. Extracellular laccase (Cplac) from C. perennis was purified to homogeneity by anion-exchange and gel filtration chromatography. Cplac is a monomeric glycoprotein with 12% carbohydrate content and a molecular mass of 66 kDa determined by polyacrylamide-gel electrophoresis. Ultraviolet-visible absorption spectroscopy observed type 1 and type 3 copper signals from Cplac. The enzyme acted optimally at pH 3-4 and 75 degrees C. Its optimal activity was with 2,2-azino-bis (3-ethylbenzothiazoline-6-sulfonate) (ABTS), it also oxidized various lignin-related phenols. The enzyme was characterized as a multi-copper blue laccase by its substrate specificity and internal amino acid sequence. It showed a higher catalytic efficiency towards ABTS (k(cat)/K-m = 18.5s(-1) mu M-1) and 2,6-dimethoxyphenol (k(cat)/K-m = 13.9s(-1) mu M-1) than any other reported laccase. Its high stability and catalytic efficiency suggest its suitability for industrial applications: it detoxified phenolic compounds in acid-pretreated rice straw and enhanced saccharification yield. (C) 2012 Elsevier Ltd. All rights reserved.