Production of xylanases from brewery spent grain and subsequent application into the spent solid residue after treatment with renewable ionic liquids for the production of sugars-containing solutions

Abstract This article describes a new three-step biorefinery process for the complete fractionation of brewery spent grain (BSG). First, BSG was assessed as a substrate for the production of enzymatic cocktails, mainly xylanases, through solid-state fermentation with Aspergillus brasiliensis. Second, the spent solid residue (SSR) recovered was delignified with cholinium glycinate ionic liquid, reducing the Klason lignin by 75.26% and the soluble lignin by 62.92%. In addition, scanning electron microscopy of the carbohydrate-rich material (CRM) showed some microfibrils and pores, which facilitated the diffusion of enzymes. Third, an enzymatic hydrolysis of the CRM was assayed with Aspergillus extracts and commercial enzyme preparations, such as Ultraflo L®, to release fermentable sugars under non-optimized conditions. Preliminary results showed that Ultraflo L® and Aspergillus extract have similar yields in the hydrolysis of glucans and xylans in BSG. No xylose, and only low amounts of glucose, were released from the SSR. Meanwhile, an improvement of the enzymatic hydrolysis in CRM was noted through the increase in saccharification of all fractions, this reaching xylan at 54.37% when Aspergillus extract was used. Although more experimental research is needed to optimize the enzymatic hydrolysis, these results illustrate the clear benefits of the integrated process proposed.