Analysis of the rumen microbiotawih resistant starch-degrading bacteria fermentation

Resistant starch (RS) reaches the large intestine without degradation, where it is decomposed by the gut microbiota. This process produces secondary metabolites including short chain fatty acids (SCFAs), which have been linked to a variety of physiological and health effects. The availability of RS as a prebiotic is a current issue. The objectives of this study were to: 1) use metagenomics to observe microbial flora changes in Bos taurus coreanae rumen fluid in the presence of RS; and 2) to isolate RS-degrading microorganisms. The major microbial strain in rumen fluid was Succiniclasticum sp., whereas Streptococcus sp. predominated after the addition of RS into the culture medium, followed by Lactobacillus sp. Bifidobacterium sp. was also continuously present. Several microorganisms with high RS granule-degrading activity were identified and isolated, including B. pseudolongum and B. choerinum. B. choerinum showed the highest RS-hydrolyzing activity and degraded almost 60% of all substrates tested. Coculture experiments demonstrated that L. brevis, which was isolated from human feces, could grow using reducing sugars generated from RS by B. choerinum. These results suggest that Bifidobacterium spp., especially B. choerinum, are the primary degraders of RS in rumen microbial flora and could be further studied as probiotic candidates.