Impact of a fermented quinoa-lentil bread on gut microbiota: An in vitro dynamic colonic fermentation study with two opposing enterotypes

The growing demand for plant-based protein products for older adults is driven by both sustainability and health benefits. Solid-state fermentation of pulses and pseudocereals improves protein digestibility, but their prebiotic potential remains underexplored, particularly in dynamic models. This study evaluated a bread prototype made from fermented quinoa and lentil flours using the twin-SHIME® (Simulator of the Human Intestinal Microbial Ecosystem) in two older adults representing distinct enterotypes. Following a stabilization and control period, the colonic compartments (proximal, PC; distal, DC) were exposed to the bread for ten days. Microbiota composition and metabolic activity were monitored throughout. While inter-individual differences in microbial shifts were observed, both simulated colonic ecosystems showed increased metabolic activity during intervention, with significantly elevated short-chain fatty acids (SCFAs) and lactate, which returned to baseline after the intervention was stopped (from day 12 onwards). One ecosystem exhibited reduced ammonium concentrations, associated with a higher initial Bacteroidota/Firmicutes ratio. Notable microbial changes included reductions in Lachnoclostridium and increases in Akkermansia and Parabacteroides —genera linked to gut barrier integrity and anti-inflammatory effects—particularly in the DC, likely due to pH differences. These results demonstrate the potential of fermented plant-based foods to beneficially modulate the gut microbiota and colonic metabolites associated with healthy ageing. However, enterotype-dependent responses highlight the importance of personalised approaches and the need for clinical validation.