Immunomodulatory Potential of Digestion-Derived Protein and Polysaccharide Fractions from Pleurotus spp. Cultivated on Agro-Industrial Residues

Lignocellulosic agricultural residues are abundant yet underutilized despite their potential for sustainable bioconversion. This study evaluated spent mushroom substrate (SMS) from Pleurotus ostreatus cultivation and roots of leafy vegetables (RLV) as alternative substrates for Pleurotus production, using wheat straw as a control. Two species, P. ostreatus and P. citrinopileatus, were cultivated on different SMS/RLV ratios and the immunomodulatory potential of harvested mushrooms was assessed. Specifically, protein (PE-D-P3 < 3 kDa) and carbohydrate (CE-D) fractions obtained after in vitro digestion were applied to LPS-challenged THP-1 cells and immune-related gene expression was analyzed by qPCR. Both species significantly modulated immune responses. The PE-D-P3 showed a more pronounced immunomodulatory effect, significantly downregulating IL1B, IL6 and TNF, whereas the CE-D reduced only TNF expression. Substrate composition influenced bioactivity: PE-D-P3 from SMS 80-RLV 20% resulted in the greatest reduction in IL1B, IL6 and TNF, while CE-D from SMS 60-RLV 40% reduced IL1B and CXCL8. These findings provide insights that both fungal species and substrate composition influence immunomodulatory compound production. Valorizing lignocellulosic residues through optimized mushroom cultivation represents a sustainable strategy for producing functional ingredients with applications in human and animal health, particularly for preventing inflammation-related disorders.