In vitro fecal fermentation outcomes of starch-lipid complexes depend on starch assembles more than lipid type

Abstract

The human gut microbiota are mostly regulated and stabilized by available macro-nutrients (carbohydrates, proteins and lipids) excursed to colonic fermentation. Resistant starch (RS) has been shown to be metabolized to specific short-chain fatty acids (SCFAs) in the colon associated with proven health benefits. However, the in vitro fecal fermentation outcomes of starch-lipid complexes (i.e., type 5 RS) and its regulation mechanism on gut microbiota are least understood. In this study, debranched high-amylose maize starches complexed with saturated fatty acids (SFAs) were in-vitro fermented by human fecal inocula and evaluated for fermentation rate, beneficial metabolite profiles as well as changes in microbiota composition. The fermentation rate of all starch-lipid complexes tested was similar and slow throughout the whole fermentation process. At the end of fermentation, the propionate concentration was significantly different between starch-lipid complex samples prepared with various SFAs. No significant difference was observed at the first three fermentation time points for the butyrate concentration, with the final concentration range of 27–33 mM. Starch-lipid complexes significantly increased the relative abundance of some beneficial gut microbiota such as Roseburia and Prevotella, and showed a closer distance with high-amylose maize starch and debranched starch rather than SFAs from the principal component analysis. Furthermore, compared with starch-lipid complexes, lauric acid and myristic acid promoted the increase of some apparently harmful gut microbiota, including Bilophila, Fusobacterium and Dialister, while palmitic acid and stearic acid did not show similar phenomenon.