In vitro fermentation characteristics of oxidized konjac glucomannan and its modulation effects on gut microbiota

Depolymerized konjac glucomannan (KGM) had better health benefits than natural KGM. Oxidation and enzymehydrolysis were two effective ways to prepare depolymerized KGM. Oxidized KGM (OKGM) and enzymehydrolyzed KGM (EKGM) varied in molecular structures, verified by nuclear magnetic resonance and atomic force microscope. The differences in chemical structure definitely influenced the fermentability of depolymerized KGM. Herein, effects of OKGM on in vitro fecal fermentation was investigated, comparing with EKGM at approximately same molecular weights. During fermentation, OKGM groups displayed slightly lower reducing sugar concentrations and higher residual carbohydrate contents than EKGM groups. After fermentation, OKGM groups produced more acetic acids and propionic acids than EKGM groups, while EKGM groups generated more butyric acids than OKGM groups. Meanwhile, relative abundances of the Firmicutes and Lactobacillus in OKGM groups were higher, while relative abundances of the Actinobacteria, Fusobacteria and Bacteroides was higher in EKGM groups. OKGM and EKGM differed in modulating gut microbiota.