Fungal oxidoreductases and CAZymes effectively degrade lignocellulosic component of switchgrass for bioethanol production.

[Display omitted] • Fungal oxidoreductases and CAZymes were produced in a bioreactor. • Laccase isozymes removed lignin up to 33.9 % from switchgrass. • Microscopic and spectroscopic analysis clearly indicated lignin degradation. • Laccase treatment improved 22.47 fold sugar hydrolysis over untreated biomass. • Fermentation studies showed high ethanol yield (78.32 % of theoretical yield). Ganoderma lucidum , a basidiomycetous fungus, has enormous potential in the co-production of diverse extracellular oxidoreductases and CAZymes. In the present study, G. lucidum MDU-7 produced 510 U/ml of laccases, xylanase (3.0 IU/ml) and cellulase (3.1 FPU/ml) in a lab-scale bioreactor. Laccase pretreatment of switchgrass in a laboratory-designed bioreactor resulted in better phenol degradation (64.27 %), lignin removal (33.9 %), and increase in cellulose crystallinity (12.66 %). The pretreatment efficacy was validated using various microscopic and spectroscopic techniques (SEM, FTIR, and XRD). The hydrolysis of laccase pretreated biomass using diverse cellulases from Aspergillus oryzae MDU-4, Aspergillus flavus MDU-5, Trichoderma citrinoviride MDU-1, and Trichoderma longibrachiatum MDU-6 resulted in 162.7 mg/g, 120.4 mg/g, 157.3 mg/g, and 176.25 mg/g release of sugars, respectively. The enzymatic hydrolysates containing 3.37–5.11 g/L sugars were fermented by Saccharomyces cerevisiae NCIM-3640 strain which resulted into 1.32–1.96 g/L ethanol, with high production yield (31.42–39.16 %). Our findings suggest that laccase pretreatment technology may provide a promising and environmentally benign alternative for the sustainable development of lignocellulosic biorefinery. [ABSTRACT FROM AUTHOR]