Optimization of Exopolysaccharide Production from Gluconobacter frateurii YY-03 Fermentation Process Enhancement and Evaluation of Its Antidiabetic Potential

This study systematically optimised the fermentation process for exopolysaccharide (EPS) production by Gluconobacter frateurii YY-03 and preliminarily explored its hypoglycaemic mechanisms. Through single-factor experiments and response surface methodology, the optimal fermentation conditions were determined as follows sucrose concentration 86.83 g/L, tryptone 15.47 g/L, and initial pH 7.18. Under these optimised conditions, the EPS yield reached 53.79 g/L, representing a 2.29-fold increase compared to pre-optimisation levels. In functional investigations, in vitro assays demonstrated that G. frateurii YY-03 EPS exhibited significant inhibitory activity against α-amylase and α-glucosidase (P < 0.05), suggesting its potential to modulate postprandial glycaemia by delaying carbohydrate digestion and absorption. Cellular experiments further revealed that the EPS significantly enhanced insulin secretion by pancreatic β-cells and stimulated the release of cholecystokinin (CCK) and glucagon-like peptide-1 (GLP-1) in enteroendocrine cells. These findings provide experimental evidence supporting the application of G. frateurii YY-03 EPS in functional food development and adjunctive diabetes therapy.