Biosynthesis of prebiotic inulins by a probiotic Lactiplantibacillus plantarum HK9 under simplified in vitro gut-like conditions

In this study, Lactiplantibacillus plantarum HK9 was identified as a probiotic strain capable of synthesizing exopolysaccharides from sucrose, with ¹³C NMR confirming these exopolysaccharides to be inulins characterized by β -(2 → 1)-glycosidic linkages. Although inulosucrase exhibited maximal activity at low temperature and acidic pH, fermentation at physiological temperature (37 °C) revealed enhanced inulin accumulation at pH 5.5. The strain also demonstrated probiotic attributes, including acid and bile tolerance and adhesion to Caco-2 intestinal epithelial cells, supporting its functional relevance in the intestinal environment. Under simplified in vitro gut-like conditions, the presence of physiological bile salts significantly promoted whole-cell–mediated bioconversion of sucrose into inulins, yielding approximately 6.2 g/L after 24 h. These findings highlight L. plantarum HK9 as a promising synbiotic candidate capable of supporting inulin production under selected gut-like conditions.