Modulatory Effects of Tetraselmis chuii Gastrointestinal Digests on Human Colonic Microbiota

Tetraselmis chuii is a microalga commercialized because of its richness in health-beneficial molecules. Previous studies have profusely demonstrated the biological properties of compounds isolated from T. chuii, but data are not yet available on the impact that gastrointestinal digestion could exert. This article describes the passage of T. chuii through the gastrointestinal tract, combining the INFOGEST procedure and in vitro colonic fermentation to examine potential effects on the human colonic microflora composition and its metabolic activity. Microbial plate counting was conducted to determine the different groups of microorganisms. Amplification of the 16S ribosomal RNA gene was performed via polymerase chain reaction to examine in detail the main genera of bacteria, and its metabolic activity was evaluated by measuring of short-chain fatty acids (SCFAs) by gas chromatography. The presence of T. chuii modified the fecal microbiota. Although the evolution of lactic acid bacteria and Enterococcus spp. content during 72 h showed that the use of T. chuii, compared to fructopolysaccharides such as inulin, would not provide nutritional advantages, the microalgae extract contributed to a significant decrease in Clostridium, Staphylococcus, and Enterobacteriaceae. Furthermore, T. chuii increased the relative abundance of Akkermansia and Butyricimonas, genera considered highly beneficial. In correlation with the presence of these microorganisms, the results show that the presence of T. chuii favored the release of SCFA, such as acetic (20 mM), propionic (>5 mM), isovaleric (0.3 mM), isobutyric (0.15 mM), and, mainly, butyric (>2 mM), after 72 h colonic fermentation, being indicators of gut health. These findings suggest that T. chuii has potential as a functional ingredient for promoting health through its modulatory effects on the intestinal microbiota.