Effects of Ganoderma-lucidum-fermented sugarcane bagasse–soybean residue substrate on the quality and starch digestibility of steamed bread

: Sugarcane bagasse and soybean residue are underutilized agricultural byproduct rich in dietary fiber. This study evaluated how fermentation of a sugarcane bagasse–soybean residue substrate with Ganoderma lucidum (FMSB) affects the quality and in vitro digestibility of steamed bread. The results revealed significant enhancements in enzymatic activities within FMSB, with xylanase, carboxymethyl cellulase, filter paper cellulase, and laccase showing increases of 117.9%, 96.3%, 140.3%, and 1566.9%, respectively. Degradation rates of the key structural components—cellulose, hemicellulose, and lignin—attained 27.5%, 42.2%, and 15.8%, respectively. Furthermore, substantial increases were observed in crude polysaccharide , flavonoidand polyphenol contents, with increments of 272.27% , 43.02% and 28.81%, respectively. FMSB addition increased the storage modulus (G′), indicating improved dough rheological properties.When FMSB is incorporated into steamed bread, it promoted ordered molecular rearrangement of starch and the formation of a gel network encapsulating starch granules, thereby limiting starch swelling and modulating its in vitro digestibility (at 6 % substitution, the predicted glycemic index (PGI) of steamed bread decreased by 7.06 % ( p < 0.05)). Overall, this study provides a theoretical basis for the value-added utilization of sugarcane bagasse–soybean residue substrate(SB-SR) and developing nutritious staple foods.