In vitro fermentation of 12 dietary fibres by faecal inoculum from pigs and humans

In vitro fermentation of 12 dietary fibres by faecal inocula from pigs and humans were performed. The fibres included homoglucans, mannans, fructans, polyuronides, and complex heteroglycans. Gas production, short chain fatty acid production and fibre degradation products were monitored during fermentation. Human inoculum has more ability to ferment resistant starch and fibres containing uronic acids. In contrast, pig inoculum is able to ferment cellulose, which is hardly fermented by human inoculum. The sugar and linkage composition of the fibres has an important influence on fibre fermentation patterns. Fibres containing uronic acids induced the production of acetate, whereas fibres containing neutral sugars induced the production of propionate or butyrate. Fermentation of the fructans showed that molecular size could be an influential factor, and fermentation of complex heteroglycans showed that the arrangement of sugars in the molecules may also affect the fermentation patterns. This experiment also shows that monitoring of fibre degradation products is important for understanding how fibres are degraded during fermentation.