In vitro fermentation pattern of D-tagatose is affected by adaptation of the microbiota from the gastrointestinal tract of pigs

Knowledge of the fermentation pattern of D-tagatose is important for the as sessment of energy value and compliance of D-tagatose. In vitro fermentatio n experiments with pig intestinal contents and bacteria harvested from the gastrointestinal tract of pigs were used to investigate the degradation of D-tagatose and the formation of fermentation products. Two groups of eight pigs were fed either a control diet containing 150 g/kg sucrose or a diet w hich had 100 g/kg of the sucrose replaced by D-tagatose, After 18 d the pig s were killed and the gastrointestinal contents collected for in vitro stud ies. No microbial fermentation of D-tagatose occurred in the stomach or in the small intestine, whereas the sugar was fermented in the cecum and colon . Formate, acetate, propionate, butyrate, valerate, caproate and some hepta noate were produced by the microbial fermentation of D-tagatose by gut micr obiota. Hydrogen and methane were also produced. The population of D-tagato se-degrading bacteria in fecal samples and the capacity of bacteria from th e hindgut to degrade D-tagatose were higher in the pigs adapted to D-tagato se compared with unadapted pigs. In unadapted pigs, the major fermentation product from D-tagatose was acetic acid. Much more butyric and valeric acid s were produced from D-tagatose by bacterial slurries of tagatose-adapted p igs compared with unadapted pigs; this was especially the case for samples from the colon. We conclude that D-tagatose is not fermented in the upper g astrointestinal tract, and the ability of the large intestinal microbiota t o ferment D-tagatose is dependent on adaptation.