Production, characterization, and bioactivities of exopolysaccharides from the submerged culture of M. H. Liu.

In this study, the submerged culture conditions for exopolysaccharide (EPS) production by M. H. Liu were screened and optimized, and the physicochemical and biological properties of EPS were investigated. Results showed that the glucose and tryptone were the best C and N sources for the maximum EPS production, respectively. Under the optimal culture conditions, the EPS production achieved 1.60 g/L at day 6 in a 5 L stirred tank reactor. Two purified fractions (i.e., Fr-I and Fr-II) were obtained from the EPS by gel permeation chromatography. Fr-II had a higher yield (87.54%), carbohydrate (95.86%), and protein (3.07%) contents and lower molecular weight (74.56 kDa) than that of Fr-I. Both Fr-I and Fr-II were polysaccharide-protein complexes with different monosaccharide compositions and chemical structures. Fr-II also exhibited stronger radical scavenging abilities, antioxidant capacities, and α-amylase and α-glycosidase inhibitory activities in vitro than that of Fr-I. Therefore, Fr-II obtained from . EPS might be explored as potential natural functional components or supplements for applications in food, medicine, and cosmetics.