The human genome expresses only a limited number of different types of digestive enzymes itself so gut microbe enzymes have a significant impact. Microbial activity is involved in breaking down foods and fermentation (converting non-starch polysaccharides to short chain fatty acids (SCFAs)) with the release of bioactive metabolites and compound synthesis.6

SCFAs such as acetate, propionate and butyrate are released by microbes from digesting plant and animal-derived carbohydrates. Butyrate is a significant energy source for gut epithelial cells and is involved in regulating human gene expression for claudin-1 and mucin. These molecules are essential for maintaining the intestinal barrier and moderating epithelial permeability, while reducing inflammatory processes and the amount of endotoxins entering the blood stream.2,6

Bifidobacterium species use carbohydrates and fatty acids to produce vitamin K. Bifidobacteria and Lactobacilli are also involved in the production of B group vitamins such as folate and riboflavin from milk fermentation, with certain strains also producing the complex vitamin cobalamin (B12).2

Microbial interaction can also occur with one species secreting compounds such as regulatory peptides (bacteriocins) and other molecules which influence the metabolic profile of other species.2