Antioxidative capacity produced by Bifidobacterium‐ and Lactobacillus acidophilus‐mediated fermentations of konjac glucomannan and glucomannan oligosaccharides

BACKGROUND: Konjac glucomannan (KGM) has been shown to stimulate the growth of bifidobacteria and lactobacilli in the human and rat colon. This study investigated the antioxidative effects produced after 48 h in vitro fermentation of unhydrolysed KGM and two hydrolysed KGM fractions (KH1 and KH2 with degree of polymerisation 10 and 5 respectively) by Bifidobacterium adolescentis, B. bifidum, B. breve, B. longum and Lactobacillus acidophilus respectively. The inhibitory effect on conjugated diene formation, ferric‐chelating capacity, α,α‐diphenyl‐β‐picrylhydrazyl (DPPH) radical‐scavenging ability and thiobarbituric acid‐reactive substances (TBARS) concentration produced by these fermentations were compared with those of oligofructose (OF) fermentation. RESULTS: The fermentation of KGM by each bacterial strain produced higher ferric‐chelating capacity of the culture supernatant compared with KH2 or OF fermentation. In contrast, the fermentation of KGM by each bacterial strain led to lower inhibition of conjugated diene formation and lower radical‐scavenging ability compared with KH2 fermentation. The fermentation of KH2 produced the lowest amount of TBARS. CONCLUSION: The fermentation of unhydrolysed KGM by colonic lactic acid bacteria in vitro produced antioxidative capacity mainly by preventing the initiation of ferrous ion‐induced peroxidation, whereas the fermentation of konjac oligosaccahrides did so by increasing the radical‐scavenging ability and eliminating lipid peroxide formation. Copyright © 2008 Society of Chemical Industry