Hydrolytic and oxidative enzymes produced by white- and brown-rot fungi during Eucalyptus grandis decay in solid medium

Abstract

Two species o brown-rot (BR) fungi and four of white-rot (WR) fungi were grown on Eucalyptus grandis wood chips under solid-state fermentation. BR fungi produced high levels of hydrolytic activities and no phenoloxidase activity, whereas WR fungi produced hydrolytic and ligninolytic enzymes, but low levels of hydrolytic activities in comparison with BR fungi. The capacity of WR fungi for wood degradation (determined as weight and component losses) seemed to be correlated with the levels of oxidative activities only after long biodegradation periods. Despite the fact that the hydrolytic activities of the two BR species were similar, Laetiporeus sulfureus demonstrated a very limited degradative capacity, contrasting with Wolfiporia cocos, which induced an effective decay. The amounts of xylanase detected in BR and WR cultures had no correlation with the extent of polyoses removal. However, the fungi providing the highest values of lignin loss were also responsible for the highest values of polyoses removal. This indicates that the lignin removal may have caused wood cell wall permeability, facilitating the xylanases diffusion into and action on the polyoses of the wood cell walls.