Fermented Food–Polysaccharides as Gut Health Regulators: Sources, Optimization, Structural Characteristics and Mechanism

Polysaccharides are natural macromolecules with significant functional properties, but the application of certain natural polysaccharides is hindered by their large molecular weight, poor solubility, and limited functionality. In recent years, microbial fermentation has emerged as a sustainable, low-energy-consuming and low-pollution green biotechnology strategy, which degrades and modifies polysaccharides by generating carbohydrate-active enzymes, thereby obtaining new types of polysaccharides with lower molecular weights and stronger functions. Meanwhile, fermented polysaccharides are utilized as prebiotics by intestinal microorganisms. By regulating microbial communities and their metabolites (such as short-chain fatty acids and bile acids), fermented polysaccharides have shown potential value in maintaining metabolic homeostasis and intervening in related diseases. Based on the results of the latest research, this paper summarizes the sources, optimization of fermentation conditions, structural characteristics of fermented food–polysaccharides, with the aim of providing new insights into the utilization of polysaccharides. Meanwhile, focuses on discussing the effects of fermented polysaccharides on the gut microbiota and the mechanisms by which they intervene in disease through regulating the microbiota and its metabolites, which offered new insights and directions for the therapeutic application of fermented food—polysaccharides.