Structural changes of butyrylated lotus seed starch and its impact on the gut microbiota of rat in vitro fermentation

Starch acylated with short-chain fatty acids (SCFAs), as type 4 resistant starch, can transport specific SCFAs to the colon and promote intestinal health. The objective was to investigate the effect of butyrylated lotus seed starches (LSBs) with different degrees of substitution (DS) on gut microbiota and butyrate production in vitro fermentation and to construct the relationship with its structural changes. The results of substrate structure change showed that the amorphous region of LSBs hydrolyzed firstly, the content of the subcrystalline region increased, and the molecular weight decreased. LSBs with higher DS had better fermentation characteristics, and more butyric acid production. A certain abundance of beneficial gut microbiota was significantly promoted. The Lotus seed resistant starch (LRS) group produced butyrate mainly by promoting the proliferation of Romboutsia. LSBs with low and medium DS mainly produced butyric acid by promoting Clostridium. LSBs with high DS produced butyric acid by promoting Lactobacillus, and Ruminococcaceae, by inhibiting Enterococcus, and Bacteroides. The study clarified the mechanism of butyric acid production was LSB's targeting the gut microbiota, which provided a scientific basis for the development of new prebiotics with high butyric acid production.