Amylopectin Partially Substituted by Cellulose in the Hindgut Was Beneficial to Short-Chain Fatty Acid Production and Probiotic Colonization

Molecular Mechanisms Underlying the Effects of Small Intestinal Fermentation on Enhancement of Prebiotic Characteristics of Cellulose in the Large Intestine

Knowledge about the prebiotic characteristics of cellulose by in vitro fermentation is not complete due to the neglect of small intestinal fermentation. This study investigated the effects of small intestinal fermentation on the prebiotic characteristics of cellulose in the large intestine and potential mechanisms through an approach of combined in vivo small intestinal fermentation and in vitro fermentation. The structural similarity between cellulose in feces and after processing by the approach of this study confirmed the validity of the approach employed. Results showed that small intestinal fermentation of cellulose increased both acetate and propionate content and enriched Corynebacterium selectively. Compared to in vitro fermentation after in vitro digestion of cellulose, the in vitro fermentation of cellulose after in vivo small intestinal fermentation produced higher contents of acetate and propionate as well as the abundance of probiotics like Ruminococcaceae_UCG-002, Blautia, and Bifidobaterium. The changes in the structural features of cellulose after in vivo small intestinal fermentation were more obvious than those after in vitro digestion, which may account for the greater production of short-chain fatty acids (SCFAs) and the abundance of probiotics. In summary, small intestinal fermentation enhanced the prebiotic characteristics of cellulose in the large intestine by predisrupting its structure.

Effects of Resistant Starch Infusion, Solely and Mixed with Xylan or Cellulose, on Gut Microbiota Composition in Ileum-Cannulated Pigs

Fermentation of dietary fiber (DF) is beneficial for gut health, but its prebiotic effects are often impeded in the distal large intestine because of the fast degradation of fermentable substrates. One way to enhance the prebiotic effect of DF is to deliver fibers to the lower parts of the gut, which can be achieved by mixing different kinds of fiber. Therefore, in the present study, an ileum-cannulated pig model was employed to investigate the fermentation influence in the large intestine by infusing resistant starch solely (RS, fast fermentable fiber) and mixing with other fibers (xylan or cellulose). Twenty-four ileum-cannulated growing pigs were divided into four groups: one control group receiving saline ileal infusions and three experimental groups infused with RS, RS with xylan, or RS with cellulose. Fecal and plasma samples were analyzed for gut microbiota composition, short-chain fatty acids (SCFAs), and blood biochemistry. Results indicated no significant differences between the RS and control group for the microbiome and SCFA concentration (p > 0.05). However, RS combined with fibers, particularly xylan, resulted in enhanced and prolonged fermentation, marked by an increase in Blautia and higher lactate and acetate production (p < 0.05). In contrast, RS with cellulose infusion enriched bacterial diversity in feces (p < 0.05). Blood biochemistry parameters showed no significant differences across groups (p > 0.05), though a trend of increased glucose levels was noted in the treatment groups (p < 0.1). Overall, RS alone had a limited impact on the distal hindgut microbiota due to rapid fermentation in the proximal gut, whereas combining RS with other fibers notably improved gut microecology by extending the fermentation process.

The functional roles of short chain fatty acids as postbiotics in human gut: future perspectives

The significance of gut microbiome and their metabolites (postbiotics) on human health could be a promising approach to treat various diseases that includes inflammatory bowel diseases, colon cancer, and many neurological disorders. Probiotics with potential mental health benefits (psychobiotics) can alter the gut-brain axis via immunological, humoral, neuronal, and metabolic pathways. Recently, probiotic bacteria like Lactobacillus and Bifidobacterium have been demonstrated for SCFAs production, which play a crucial role in a variety of diseases. These acids could enhance the production of mucins, antimicrobial proteins (bacteriocins and peptides), cytokines (Interleukin 10 and 18) and neurotransmitters (serotonin) in the intestine to main the gut microbiota, intestinal barrier system and other immune functions. In this review, we discuss about two mechanisms such as (i) SCFAs mediated intestinal barrier system, and (ii) SCFAs mediated gut-brain axis to elucidate the therapeutic options for the treatment/prevention of various diseases.