An unexplored enzymatic source for Brewer's spent grain valorization: The role of wood-substrate beetle-associated fungi and endophytes

Abstract

This study investigates the valorization of brewer's spent grains (BSG), a major solid waste byproduct of the brewing industry, by exploring its potential for the production of valuable products, such as lignocellulolytic enzymes and fermentable monosaccharides. To achieve this, the research examines the combination of underexplored filamentous fungal isolates as enzyme sources and evaluates their effectiveness in BSG saccharification processes to enhance the recovery of these valuable compounds. Initially, the enzyme activities of amylase (AMI), endoglucanase (EGA), ligninase, and xylanase (XA) produced by four fungal strains associated with the ambrosia beetle Megaplatypus mutatus and a fungal wood endophyte of Platanus acerifolia were studied. Among these, Filobasidium aff. oriense (Filobasidium 4796) was selected based on its enzyme production capabilities and used to conduct solid-state fermentation (SSF) with BSG as the substrate. The enzymatic extract (EE) of Filobasidium 4796 showed maximum activities of 7.13 IU/gram of dry substrate (gds) for AMI, 3.39 IU/gds for EGA, 356.24 IU/gds for XA, and 2.44 IU/gds for filter paper activity (FPA). Subsequently, the EE of Filobasidium 4796 was evaluated for the saccharification of BSG pretreated with H2O2 under acidic conditions, resulting in the release of 149.25 mg sugars/g dry BSG. These findings highlight the significant potential of Filobasidium 4796 as an alternative source of lignocellulolytic enzymes and emphasize the value of utilizing fungal strains from unconventional sources for industrial enzyme production and the bioconversion and revalorization of a lignocellulosic waste.