Valorization of lignocellulosic wastes for extracellular enzyme production by novel Basidiomycetes: screening, hydrolysis, and bioethanol production

Abstract

This study aimed at the exploitation of lignocellulosic wastes for the evaluation of the newly isolated white-rot fungal strains enzymatic potential for bioethanol production. The isolates belonging to Basidiomycetes, Fomes fomentarius TMF2, Schizophyllum commune TMF3, and Bjerkandera adusta TMF1, could synthesize extracellular laccase and various hydrolase while growing on lignocellulosic waste materials. More specifically, for the first time, F. fomentarius TMF2 synthesized laccase using sunflower meal as a substrate. This substrate could stimulate B. adusta TMF1 for carboxymethyl cellulase and Avicelase production. The isolate B. adusta TMF1 was able to produce amylase during its growth on brewer's spent grain, which is up to now the best result reported for this activity of any B. adusta strain. Soybean meal was the most potent substrate for stimulating pectinase production by B. adusta TMF1 and S. commune TMF3. While growing on brewer 's spent grain, B. adusta TMF1 and S. commune TMF3 produced high levels of xylanase. Spent coffee residues were for the first time tested as a substrate for hydrolase production by selected fungal species. Also, this is the first attempt where the produced enzymes by isolate B. adusta TMF1 were used for lignocellulose hydrolysis of brewer's spent grain and corn stover for bioethanol production, where under non-optimized conditions 0.94 g/L and 0.86 g/L of bioethanol could be produced, respectively. This study showed that novel white-rot fungal isolates, especially B. adusta TMF1, could grow on unexploited, low-cost lignocellulosic substrates and to produce biotechnological value-added products within environmental and economical accepted processes.