Diet: Microbiota Interaction in the Gut-Focus on Amino Acid Metabolism

Abstract

This study aims to measure the impact of protein and amino acid fermentation on the composition and metabolic output of gut microbiota. Although dissimilatory pathways have been described for most amino acids, microbial degradation routes within the gut microbiota are relatively unexplored. The objectives were (1) to characterize amino acid breakdown by the colonic microbiota, (2) to determine the fermentation products formed from individual amino acids/protein (3) to examine how amino acid metabolism is impacted by the presence of a fermentable fiber (prebiotic inulin) and finally (4) to evaluate with an in vivo model (trout fish) diet:microbe interactions and the development of gut microbiota during fish farming. Interactions between the healthy human intestinal microbiota of the distal colon and different combinations of nutrients were simulated using in vitro pH-controlled anaerobic batch cultures of human faeces. Combining high-throughput sequencing of 16S rRNA amplicons, with high-throughput 1H NMR, changes in faecal microbiota composition and metabolic output were measured. During exogenous substrate microbial fermentation (e.g. beef, Trp or fish feed) in the large bowel bioactive compounds (harmful or beneficial) are produced. Many factors affect the gut-microbial metabolism including pH, type and quantity of growth substrate (e.g. protein/carbohydrate) and make up of the gut microbiota. Considerable interindividual variation was observed in response to different digested substrates but over all, the beneficial impact of prebiotic fiber fermentation on production of bioactive compounds from amino acids/proteins was confirmed in this study. In trout, although our dietary intervention with essential oils had little impact on the gut microbiota, the study showed for the first time a dramatic shift in the composition and diversity of the gut microbiota in juvenile, compared to adult fish. Thse observations may have relevance in designing dietary strategies to reduce chronic diseases like colon cancer and heard disease and for fish farming respectively.