Effects of nonionic surfactants on the production of extracellular polysaccharides, citrinin synthesis, physicochemical structural characteristics, and in vitro hypoglycaemic activity of Monascus purpureus YY-1

Monascus extracellular polysaccharides exhibit diverse bioactivities, including antioxidant, antitumor, and immunomodulatory effects. Nevertheless, their low native yield restricts practical applications. To improve the fermentation yield and functional properties of EPS, Monascus purpureus YY-1 was employed as the experimental strain in this study. We systematically investigated the regulatory effects of three nonionic surfactants (Triton X-100, Brij 35, and Span 60) on EPS production, citrinin accumulation, physicochemical structures of polysaccharides, and their in vitro hypoglycemic activity of the strain. The results demonstrated that nonionic surfactants significantly elevated EPS yields by enhancing fungal cell membrane permeability, achieving an overall increase of 10%-20% relative to the blank control group. Meanwhile, these surfactants effectively inhibited the biosynthesis and accumulation of citrinin during fermentation, improving product safety. Among these, the polysaccharides (T-EPS) obtained with Triton X-100 exhibit higher total sugar content, a more favorable galactose-to-mannose ratio, lower average molecular weight and particle size, and display a typical triple-helix conformation and a loose, porous micro-morphology. These favorable physicochemical structural features confer T-EPS with stronger inhibitory activities against α-amylase and α-glucosidase, as well as superior glucose adsorption capacity. This study confirms that nonionic surfactants (especially Triton X-100 with optimal performance) can synergistically enhance the yield, safety, and hypoglycemic activity of Monascus EPS. It provides important theoretical support for the development and application of functional polysaccharides from Monascus in the field of hypoglycemic functional foods.