Acid production and conversion of konjac glucomannan during in vitro colonic fermentation affected by exogenous microorganisms and tea polyphenols

Abstract

Impacts of exogenous microorganisms and tea polyphenols on acid production and conversion during in vitro colonic fermentation of konjac glucomannan (KGM) were assessed in this study. Colonic fermentation of KGM by the fecal extract of healthy adults resulted in a propionate-rich profile, as acetic, propionic, butyric and lactic acids production were 16.1, 13.0, 3.3 and 20.2 mmol/L, respectively. Inoculation of one of ten exogenous microorganisms in the fermentative systems increased acetic, propionic and butyric acids production by 50−230%, 9−190% and 110−350%, respectively, and also accelerated lactic acid conversion by 14−40%. Tea polyphenols in the fermentative systems showed clear inhibition on both acid production and conversion; however, this inhibition could be partially or mostly antagonised by the inoculated exogenous microorganisms, resulting in improved acid production and conversion. In total, Lactobacillus brevis and Sterptococcus thermophilus were more able to increase acid production, and the propionate-rich profile was not changed in all cases.