Fungal lignocellulolytic enzyme profiling: evaluating the potential for enhancing brewer’s spent grains saccharification

Abstract

Brewer's spent grains (BSG), a major brewing byproduct, have gained attention as a sustainable source of structural carbohydrates convertible into second-generation (2 G) sugars for fermentation processes. This study evaluates BSG as a substrate for lignocellulolytic fungi isolated from Mexico and characterizes their enzymatic activity in biomass degradation. BSG compositional analysis revealed 37.47 % cellulose, 8.74 % hemicellulose, and 17.48 % lignin, supporting its potential as a feedstock for bioconversion. Solid-state fermentation (SSF) using BSG assessed the enzymatic activities of Trichoderma atroviride (NBRC 101776), Trichoderma longibrachiatum isolate PC1 (MK910052.1), and Penicillium rubens (CBS 129667). These strains were isolated and identified through ITS sequencing, with additional TEF1 sequencing performed for species confirmation within the Trichoderma genus. T. atroviride exhibited the highest cellulase and xylanase activities (FPase: 0.488 U/mL, β-glucosidase: 0.055 U/mL, xylanase: 0.125 U/mL), while P. rubens showed the highest mannanase activity (0.419 U/mL). Sodium Dodecyl Sulphate Polyacrylamide Gel Electrophoresis analysis was performed on crude and partially purified enzyme extracts, revealing distinct bands corresponding to cellulases, β-glucosidases, amylases, and xylanases in Trichoderma spp., and suggesting the production of β-glucosidases and xylanases by P. rubens. This study contributes to the sustainable utilization of BSG and highlights the potential of native fungal strains for enhanced enzyme production in lignocellulosic biomass valorization.