Valorization of mushroom by-products for sustainability: exploring antioxidant and prebiotic properties

Agaricus bisporus (white button mushroom), Pleurotus ostreatus (oyster mushroom), and Lentinula edodes (shiitake mushroom) are the most cultivated mushrooms in the Spanish region of Castilla-La Mancha. The increasing production of these mushrooms has created opportunities for sustainable utilization of their by-products such as undersized mushrooms, stalks, and stems. This study evaluated the antioxidant, prebiotic, and antimicrobial properties of aqueous, ethanolic and alkaline extracts derived from these by-products. Aqueous extracts from oyster mushroom, rich in glucose-polysaccharides (59.4±0.4% mushroom dw), promoted the growth and lactic acid production of the probiotic bacteria Lactocaseibacillus casei and Lactoplantibacillus plantarum . Shiitake extracts demonstrated antimicrobial activity against Pseudomonas aeruginosa , Escherichia coli and Salmonella enterica (Minimal inhibitory concentrations: 15, 7.5 and 7.5 mg/mL, respectively), and stimulated the growth of lactic acid bacteria at low concentrations (1.875 mg/mL) but inhibiting them at higher concentrations. Extracts from white button mushrooms exhibited the strongest antioxidant activity, particularly ethanolic extracts rich in phenolic compounds (0.015 mg Gallic acid/mg extract). These results highlight the potential of extracts of mushroom by-products as organic sources of antioxidants, antimicrobials, and prebiotics, creating new avenues for food product development. Reusing these by-products could encourage sustainability and assist the mushroom sector in implementing zero-waste and circular economy methods.