Structural Dynamics, Gut Microbiota Modulation, and Immunological Impacts of Shiitake Mushroom β-Glucan during In Vitro Intestinal Fermentation
Huanhuan Liu, Qiannan Wang, Lin Zeng, Yongshuai Liu, Yiheng Zhang, Zhenou Sun, Qingbin Guo, Steve W. Cui
Abstract
This study investigated the structure–function relationship of shiitake β-glucan (SBG) through simulated digestion and colonic fermentation. SBG, composed of β-(1 → 3)-linked glucan backbones with β-(1 → 6)-linked side chains, exhibited notable resistance to enzymatic and acidic degradation in the upper gastrointestinal tract. During in vitro colonic fermentation, 59% of carbohydrates were consumed within 48 h, with a significant pH reduction and a 1.5-fold increase in short-chain fatty acid production. Microbiome analysis demonstrated that SBG enhanced Bacteroides and Lactobacillus populations, while suppressing Escherichia-Shigella . Within the first 12 h, SBG maintained a rigid triple-helix structure, with a slight decrease in branching from 48.02 to 44.26%. After 24 h, the triple helix unwound, and extensive depolymerization of the backbone occurred by 48 h. Immunomodulatory activity was preserved early in fermentation but decreased as the triple-helix structure broke down. These findings emphasize the critical role of molecular rigidity and conformational integrity in β-glucan’s functionality for food and therapeutic applications.