COMPARISON OF INVITRO PRODUCTIVITIES OF SHORT-CHAIN FATTY-ACIDS AND GASES FROM ALDOSES AND THE CORRESPONDING ALCOHOLS BY PIG CECAL BACTERIA

We studied patterns of gas-release and short-chain fatty acids (SCFA) production from aldoses (D-glucose and D-xylose) and their alcohols (D-sorbitol and D-xylitol) by a batch culture technique using pig cecal bacteria. The hydrogenation of aldoses elongated the lag time by 3-10 hr and retarded the rate of fermentation. The productions of SCFA from aldoses (86.5 and 114.9-mu-moles, respectively) were greater than those from their alcohols (40.1 and 2.5-mu-moles, respectively) of the same weight (10 mg) during 8 hr of incubation and the same variance was observed during 24 hr of incubation. Productions of SCFA from pentoses were greater than those from hexoses during 24 hr of incubation (P < 0.05). Hydrogenation of aldoses influenced molar proportions of produced SCFA (acetic:propionic:n-butyric acids). At 24 hr of incubation the molar proportions from D-glucose and D-sorbitol were 38:55:8 and 25:71:4, respectively. These results suggest that hydrogenation of aldoses slows down the fermentation rate (production of SCFA) and that sugar alcohols may escape the microbial breakdown during the colonic transit.