Valorization of brewer's spent grains through Ganoderma lucidum cultivation: Functional food ingredients and bread prototypes

Brewer spent grain (BSG) is the primary by-product of beer production, representing 85% of total waste in this industry. This study aimed to valorize BSG by incorporating it into the cultivation medium for Ganoderma lucidum to develop functional food ingredients with enhanced techno-functional and nutritional properties, particularly focusing on fiber and protein content. The following four samples were analyzed: (1) 100% BSG, (2) 50% BSG and 50% commercial fungal medium (Mix), (3) lyophilized biomass of G. lucidum , and (4) oven-dried biomass of G. lucidum (OGB). BSG had the highest fat (6.17 ± 0.26 g·100 g −1 db), protein (19.66 ± 0.80 g·100g −1 db), soluble dietary fiber (15.87 ± 0.76 g·100g −1 db) and carbohydrate levels (29.99 ± 0.60g·100 g −1 db). The Mix demonstrated the highest total fiber content (70.02 ± 0.62 g·100 g −1 db) and insoluble dietary fiber (63.15 ± 0.71 g·100 g −1 db). Four prototypes were created by partially substituting wheat flour with different percentages of BSG and OGB in traditional bread recipes. A 7-point hedonic scale assessed appearance, odor, texture, and taste, and a 5-point Likert scale rated overall acceptance. Samples A1 and B2 had the highest scores across hedonic attributes (>6). B2 excelled in overall acceptance (4.36), while D2 scored the lowest (2.89) due to its bitter taste, most likely derived from the presence of fungal triterpenoids. • Brewer's spent grain (BSG) is a major by-product (85%) but is underutilized. • BSG incorporated into Ganoderma lucidum for enhanced nutritional properties. • Ingredients from BSG and Ganoderma showed improved fiber and protein content. • BSG-enriched breads had the highest sensory acceptance scores. • BSG is suggested for sustainable food production and circular economy use.