Effects of molecular weight and degree of branching on microbial fermentation characteristics of okra pectic-polysaccharide and its selective impact on gut microbial composition

In this study, the microbial fermentation characteristics of okra pectic-polysaccharide (OPP) and its degraded products (DOPP-1 and DOPP-3) with different molecular weights (Mw) and degrees of branching (DB) were investigated, and related impacts on gut microbial composition were also revealed. Results indicated that microbial fermentation characteristics of OPP were obviously affected by its different structural features. The fermentabilities of OPP (high Mw and DB), DOPP-1 (middle Mw and DB), and DOPP-3 (low Mw and DB) were measured to be 49.49%, 58.34%, and 48.16%, indicating that the utilization of total carbohydrates of DOPP-1 was relatively higher compared to OPP and DOPP-3. The ways in which gut bacteria metabolized OPP, DOPP-1 and DOPP-3 were quite different, and a lower Mw and a higher DB were more beneficial to the fermentation by intestinal bacteria. Additionally, selective modulations of gut microbial composition by different types of okra pectic-polysaccharides were observed. Both OPP and DOPP-1 could increase relative abundances of several beneficial bacteria, such as Bacteroides and Phascolarctobacterium. While DOPP-3 could notably improve relative abundances of Megasphaera and Megamonas. Results suggested that the modulation of gut microbiota by okra pectic-polysaccharide was structure-dependent, and both DB and Mw played critical roles in the selective modulation of gut microbial composition. Collectively, our findings are beneficial to revealing the potential relationship between chemical structures of OPP and its gut microbial fermentation characteristics, which are also helpful for the design of potential OPP for selective modulation of beneficial bacteria in the gut.