Optimisation of exopolysaccharide production from <i>Gluconobacter frateurii</i> YY-03 fermentation process enhancement and evaluation of its antidiabetic potential

Abstract This study optimised the fermentation process for exopolysaccharide (EPS) production by Gluconobacter frateurii YY-03 and explored its hypoglycaemic mechanisms. Using single-factor experiments and response surface methodology, the optimal fermentation conditions were determined as 86.83 g/L sucrose, 15.47 g/L tryptone, and an initial pH of 7.18. Under these optimised conditions, the EPS yield reached 53.79 g/L, representing a 2.29-fold increase compared to preoptimisation levels. In functional investigations, in vitro assays demonstrated that G. frateurii YY-03 EPS inhibited α-amylase and α-glucosidase, suggesting delayed carbohydrate digestion P &amp;lt; 0.05. In cell models, EPS enhanced insulin secretion in RIN-m5f β-cells and promoted cholecystokinin and GLP-1 release in STC-1 enteroendocrine cells. These results support the potential of G.frateurii YY-03 EPS for functional food development and as an adjunct for diabetes management.