Valorization of brewer's spent grain by different strategies of structural destabilization and enzymatic saccharification

Abstract

The valorization of brewer's spent grain (BSG), the main solid waste from this industry, is a topic of concern. The structural modifications generated by physicochemical pretreatments (autohydrolytic, H2O2 and H2SO4) to promote enzymatic accessibility and thus exploit this residue were assessed by Fourier transform infrared spectroscopy, thermogravimetric analysis and scanning electron microscopy. After the pretreatments, a saccharification stage was conducted by an enzyme cocktail generated with high productivity (1.52 IU/(gds*d) filter paper activity, FPA, and 1.55 IU/(gds*d) endoglucanases, EGA, and 48.37 IU/(gds*d) xylanases) by Trichoderma reesei with BSG as substrate. Biomass recovery and sugar yields after pretreatments were consistent with hemicellulose and lignin removal and structural alterations generated. When the BSG was treated with H2O2 the enzymatic sugar release is efficient, obtaining 193.35 mg sugars/g dry BSG. Thus, conducting this pretreatment with H2O2 at low pH (5.0) and its combination with enzyme saccharification represents a promissory novel strategy to enhance the potential exploitation of this residue, using an economical and environmentally safe process.