Elucidating molecular structure and prebiotics properties of bioengineered α-D-glucan from Leuconostoc citreum SK24.002

The objective of this work was to produce the bioengineered α-D-glucan from Leuconostoc citreum SK24.002 and study its molecular structure and prebiotics properties. The connectivities and substitutions of α-D-glucan were measured using 2D NMR and the chain structure of the repeating unit was deduced. During in vitro fecal fermentation, a strong increase in bacterial population was observed and the largest changes took place during the first 24 h of incubation. A decrease pH (approximately 2.0) was also observed for the fermentation from 0 h to 48 h compared to the blank (pH 6.8-6.6). Total short-chain fatty acid (SCFA) increased during batch fecal fermentation in the presence of α-D-glucan and it reached the maximum level of 30.01 mM after 48 h of fermentation. The lowest gas production and highest butyric acid production at 48 h of incubation was recorded with α-D-glucan as compared with dextran or pullulan. Moreover, human fecal microbiota on α-D-glucan produced more butyric acid between 24 and 48 h than other test carbohydrates. These results suggest that α-D-glucan would be a good candidate slowly fermentable fiber and may have a positive effect for the gut microbiota homeostasis.