Effects of partially hydrolyzed guar gums of different molecular weights on a human intestinal in vitro fermentation model

Partially hydrolyzed guar gums (PHGGs) are prebiotic soluble dietary fibers. High molecular-weight PHGGs have rapid fermentation and high short-chain fatty acid (SCFA) productivity rates, compared to low molecular-weight PHGGs. Therefore, low molecular-weight PHGGs may have less pronounced prebiotic effects than high molecular-weight PHGGs. However, the effects of PHGGs of different molecular weights on the human intestinal microbiota, as well as their fermentation ability and prebiotic effects, have not been investigated. The aim of this study was to evaluate the effects of two PHGGs of different molecular weights, Sunfiber-R (SF-R; 20 kDa) and Sunfiber-V (SF-V; 5 kDa), on human colonic microbiota and SCFA production. A human intestinal in vitro fermentation model was operated by fecal samples with and without the PHGGs. The addition of 0.2% SF-R or SF-V increased the relative abundance of Bacteroides spp., especially that of Bacteroides uniformis. This increase corresponded to a significant (p = 0.030) and non-significant (p = 0.073) increase in propionate production in response to SF-R and SF-V addition, respectively. Both fibers increased the relative abundance of Faecalibacterium and stimulated an increase in the abundance of unclassified Lachnospiraceae and Bifidobacterium. In conclusion, the low molecular-weight PHGG exerted prebiotic effects on human colonic microbiota to increase SCFA production and bacteria that are beneficial to human health in a manner similar to that of the high molecular-weight forms of PHGG.