Beneficial impact of raffinose on human intestinal microbiota

Abstract

Until now the prebiotic potential of pure trisaccharide raffinose on human health remains poorly investigated. In particular, studies following the guidelines recently established by the International Scientific Association for Probiotics and Prebiotics are scarce [1]. Raffinose is non-digestible to humans but can be metabolized by colon bacteria [2], therefore being considered a prebiotic candidate. Different approaches for testing the prebiotic potential of new compounds have been described. However, an in vitro model is considered a more suitable first-stage strategy to screen prebiotics candidates [3], contrarily to in vivo studies which are expensive and time-consuming. In this work, an in vitro model using human fecal inocula of two healthy volunteers (D1 and D2) was used to study the prebiotic potential of raffinose and compare it with the well-stablished and commercial prebiotic lactulose. The intestinal microbiota showed preference for raffinose as substrate presenting the highest consumption value at 48 h (96.0 ± 0.9 % D1 and 95.3 ± 0.7 % D2). The fermentation of raffinose decreased the medium pH, the ammonia concentration and the relative amount of Proteobacteria, including Escherichia coli, while increasing the total production of lactate and short chain fatty acids, viz. acetate and propionate, (129.9±2.6 mM D1 and 179.6±0.6 mM D2), CO2 (10.8±0.8 mmol/Lmedium D1 and 5.2±0.3 mmol/Lmedium D2) and the relative amount of Bifidobacterium and Lactobacillus. This study strongly suggests that raffinose holds potential prebiotic properties for human health and, subsequently, potential to be commercialized as functional food ingredient.