In vitro fecal fermentation characteristics of mutant rice starch depend more on amylose content than crystalline structure

To obtain the relation between rice starch features and fermentation characteristics, rice starches with various polymorphic types and apparent amylose contents were subjected to in vitro fecal fermentation. Gas and short-chain fatty acid production was evaluated as a function of fermentation time, and the microbial responses were monitored by 16S rRNA sequencing technique at the end of fermentation. Regardless of polymorphic type, three high-amylose mutant rice starches (i.e., GM03, A-type; BP577, B-type; Wx21TT, C-type) displayed significantly slower fermentation rate during the first 12 h and higher final butyrate yield (17.6-17.9 mM) compared to the A-type normal starches (9311 and Wx22TT), and promoted the proliferation of Roseburia. However, A-type normal rice starches presented higher propionate production, and increased the growth of Bacteroides and Megamonas. The principal component and redundancy analyses indicated that three high-amylose mutant rice starches showed similar abundance and migration of microbial communities, and the apparent amylose content was closely correlated with the abundance of their five key amplicon sequence variants. Our results demonstrated that amylose content might be a controlling factor in determining the fermentation properties of rice starches than crystalline structure.