Resistant starch type 2 and whole grain maize flours enrich different intestinal bacteria and metatranscriptomes

The intestinal microbiota of Sprague-Dawley (SD) rats were investigated following consumption of diets containing refined high-amylose cornstarch (RS), waxy whole-grain flour from maize (WG), or high-amylose whole-grain flour (WG + RS) together with moderate (MF, 30% of energy) or high (HF, 42% of energy) levels of fat. Compared with control (CON) diets, RS reduced bacterial alpha-diversity and enriched Bacteroidetes and WG increased Lactobacillus proportions by three-fold. WG + RS conferred a combined effect, but the changes were attenuated and greater inter-individual variation was observed. Proportions of fiber-degrading bacterial taxa were inversely correlated with cecal pH. Notably, there was little influence of fat intake on the cecal microbiota. Examination of cecal metatranscriptomes showed that WG and CON diets resulted in similar microbiomes. RS consumption was associated with an increased abundance of either Bacteroides or Prevotella transcripts. Metatranscriptomes of RS-fed rats were consistently enriched in transcripts encoding chaperones, glutamate decarboxylases and glutaminases, and starch degradative enzymes.