EFFECTS OF GLUCONIC ACID ON HUMAN FECAL BACTERIA

Gluconate was fermented selectively by the Bifidobacterium adolescentis group and some species of other genera, including Clostridium clostridiiforme, C. innocuum, Propionibacterium acnes, Megasphaera elsdenii, Enterococcus faecium and Klebsiella pneumoniae; however it was not utilised by most other bacteria including the Bacteroidaceae. No other organic acid salts were utilised by B. adolescentis. These salts weakly inhibited the growth of C. perfringens in vitro, as did gluconate. The absorption rate of gluconate from the ligated small intestinal loop in rats was 19.9 per cent under conditions when 100 per cent of glucose was absorbed. The effects of ingestion of gluconate on human faecal bacteria was studied in ten healthy adult males. They ingested 9 g/d or 3 g/d of glucono-delta-lactone (anhydride of gluconic acid). With the 9 g/d ingestion, the number of bifidobacteria significantly increased (P<0.001), whereas C. perfringens decreased and Enterobacteriaceae remained constant. The concentrations of bifidobacteria also increased (P<0.05) following 3 g/d ingestion.