Enzymes Involved in Lignocellulose Decomposition and Effects of Fungal Pretreatment During Solid-state Fermentation of Lignocellulosic Agricultural Residues: The Case of Trametes versicolor

Ligninolytic fungi are considered useful for different biotechnological uses such as lignocellulose pretreatment for biorefinery applications, composting, mushroom production, or bioremediation purposes. Enzymes contributing to lignocellulose breakdown represent valuable biocatalysts. Trametes versicolor is a well-known ligninolytic white-rot basidiomycete capable of growing on different lignocellulosic materials. In the present study, the use of T. versicolor, which secretes several enzymes capable of degrading lignocellulosic biomass, was evaluated from two biotechnological aspects including fungal crude extracts and effects on enzymatic saccharification of wheat straw. We used 20-day-old wheat straw cultures of this fungus to characterize its lignocellulose-decomposing multi-enzyme complex. At the end of the cultivation period, losses of approximately 41% in lignin and 30% in total dry mass were observed relative to their initial values. A total of 17 enzyme activities, each acting differently on the polysaccharide components of the lignocellulosic substrate, and lignin-modifying enzyme activities (laccase, peroxidases) were investigated in aqueous extracts of fungal cultures. The activities of carboxylesterase (substrate: 4-nitrophenyl valerate), endo-1,4-β-D-glucanase (substrate: 2-hydroxyethylcellulose), and laccase were found to predominate. In summary, fungal crude extracts containing different enzyme activities may be promising for various biotechnological purposes. Trametes versicolor effectively pretreated wheat straw, significantly increasing reducing sugar levels compared to controls.