Effect of redox status on the metabolic characteristics and microbiota composition of high-amylose maize starch during in vitro fermentation.

We investigated the effects of continuous redox gradients (0-12% O2) on the metabolic profiles of high-amylose maize starch (HAMS) in an in vitro human fecal fermentation system. After 24 h fermentation, total short-chain fatty acid production remained stable under mild oxidation (2% O2). However, a clear metabolic shift occurred: acetate proportions increased from 25.70% to 32.55%, whereas butyrate declined from 16.19% to 9.88%. Under high oxidation (12% O2), total fermentation was markedly suppressed (from 52.69 to 15.25 mmol/L), with metabolism shifting drastically toward acetate (69.09%) over butyrate (2.18%). This shift resulted from the selective enrichment of facultative anaerobes and acetate producers (e.g., Klebsiella and Parabacteroides) and the depletion of strict anaerobic butyrate producers (e.g., Butyricicoccus). Functional predictions revealed that oxidative stress redirected microbial metabolism from anaerobic fermentation to aerobic stress-response pathways. Overall, redox status critically shapes the HAMS fermentation profile, offering a theoretical foundation for redox-targeted dietary interventions with HAMS.