The effects of dietary fibres on microbial fermentation profiles by in vitro assessment using pig colonic digesta

This thesis has investigated in vitro fermentation profiles of soluble soybean polysaccharides (SSPS) and soluble flaxseed gum (SFG) by pig colonic digesta with inulin as the reference fibre. All fibre grown cultures showed a significant increase in total short chain fatty acid production, with the highest level of butyrate in SSPS grown cultures after 24 h incubation and the highest level of acetate and propionate in SFG grown cultures after 48 h incubation. Polymerase chain reaction (PCR) and denaturing gradient gel electrophoresis (DGGE) analysis of 16S rRNA genes revealed that the bacterial community structure was influenced by types of fibres. The population of major bacterial groups can also be altered by these fibres. Quantitative PCR analysis showed that SSPS enhanced the population of Bifidobacterium by more than 4 fold and SFG increased the abundance of Bacteroidetes by more than 1.6 fold during the fermentation. Together, SSPS and SFG demonstrated beneficial effects towards colonic health during the fermentation. Further in vivo studies are required to verify their physiological effects to promote the use of SSPS and SFG in functional fibre-fortified food products.