Production of acids from inulin by a mixed culture of rumen microorganisms

The production of volatile fatty acids (VFA) and lactic acid from inulin (plant fructan with 2-1 bonds) in in vitro rumen fermentations was followed. The experiments were performed with inocula from wethers receiving two rations, with two pH regimes and using as inocula either whole rumen contents or the corresponding rumen fluid. The following results were obtained: The VFA production was higher when using inocula from hay and concentrate fed wethers. In contrast to this, the lactic acid production was higher when using inocula from hay fed wethers. The VFA production tends to be higher in a weakly acid medium than in a neutral medium. Acetate-to-propionate molar ratio was lower at lower pH. The amounts and composition of the VFA were not different when using both types of inocula. Thus, we believe that micro-organisms colonising plant fibres obviously do not play an important role in inulin splitting.