In vitro colonic fermentation of red kidney beans depends on cotyledon cells integrity and microbiota adaptation

In the present study we investigated the effect of cellular integrity on microbial utilization of proteins and carbohydrates by gut microbiota. Cotyledon cells from red kidney beans with different levels of structural integrity were fermented in-vitro by microbial communities previously adapted to the conditions of ascending, transverse and descending colon. The effect of bacterial adaptation to substrate was also assessed by using microbiota exposed to a diet rich in bean cells. Microscopy analyses indicate that cell integrity was maintained during fermentation. The amount of gas generated and the rate of total gas production was higher in broken cells compared to intact cells which suggest a faster and more extensive utilization of nutrients when cell wall is broken. A significantly higher butyric and propionic acid level was detected in broken cells at the end of the fermentation. Moreover, adapted bacterial communities were more efficient in fermenting bean cells where higher amounts of butyrate were produced in all colon regions independently of sample integrity. Bacterial communities of the distal colon appeared to be the most efficient in carbohydrate and protein fermentation as witnessed by the higher levels of gas, and short chain fatty acids. It was also found that cell integrity and adaptation to bean cells modulate the hierarchy of nutrient utilization, with non-starch polysaccharides preferred over starch and proteins by microbiota exposed to bean cells. Our results demonstrated that structural aspects of foods, such as cell integrity in plant tissues, may modulate nutrients utilization by gut microbiota.