Effects of pig colonic digesta and dietary fibres on in vitro microbial fermentation profiles

Abstract The effects of soluble soybean polysaccharides (SSPS) and soluble flaxseed gum (SFG) on the production of short chain fatty acids (SCFA) and other acids as well as bacterial communities during in vitro fermentation by pig colonic digesta were investigated with inulin as the reference fibre. Digesta samples from different ages of pigs (2-month- versus 7-month-old) that exhibited different PCR–DGGE (polymerase chain reaction–denaturing gradient gel electrophoresis) bacterial profiles were initially examined for their influence over Lactobacillus and Bifidobacterium populations when used as an inoculum. The influence of digesta from 7-month-old pigs was more obvious and thus chosen for the remaining experiments. All fibre-grown cultures showed a significant increase in acid production compared to the control cultures that contained no fibres. SFG was less degradable than SSPS and inulin by bacteria from the digesta. Inulin-grown cultures produced mainly lactate and SSPS- and SFG-grown cultures generated largely acetate. While SFG appeared to support the production of propionate, SSPS and inulin shared a similarity in favouring butyrate production. PCR–DGGE and quantitative PCR (QPCR) analyses indicated that types of dietary fibre were able to dictate bacterial communities during the fermentation. Both inulin and SSPS were shown to enrich Bifidobacterium . Unlike inulin, SSPS had no enrichment toward Lactobacillus . SFG was able to enrich Bacteroidetes . While the fermentability and bacterial selection of dietary fibres suggest their potential application in fortifying food products, the impact of digesta from different ages of pigs on fermentation/microbiota patterns highlights the need for consideration of ages in further studies of nutritional values of dietary fibres towards colonic health.