Solid-state fermentation for enhanced brewers‘ spent grain protein valorisation: A comprehensive review of conventional and emerging techniques

Abstract

Growing demand for sustainable plant-based protein sources has increased in recent years. Brewers’ spent grain (BSG), the most abundant brewing by-product by volume, has attracted considerable attention due to its high protein content (18 to 30%) and its desirable physicochemical and nutritional properties. In this review, the advantages and limitations of conventional and novel BSG protein (BSGP) extraction techniques were discussed and compared. Solid-state fermentation (SSF) was highlighted as a sustainable and industrially adaptable biological process that enhances protein accessibility and recovery for waste valorisation. The commercial
viability of SSF-regulated BSG bioconversion, key operational factors and future insights were also examined. Overall, this review provides an updated evaluation of BSG protein extraction methods, thereby contributing to the advancement of sustainable resource utilization and promoting circular bioeconomy.