Evidence of synbiotic potential of oat beverage enriched with inulin and fermented by L. rhamnosus LR B in a dynamic in vitro model of human colon

Abstract

Fermented dairy products are known for their efficiency in delivering and protecting probiotic microorganisms. However, there is a growing demand for diversification of the market with plant-based products. The aim of this study was to develop an oat beverage enriched with inulin and fermented with Lacticaseibacillus rhamnosus LR B and evaluate its synbiotic effects in vitro. For this purpose, the validated dynamic colon model (the TNO Intestinal Model TIM-2) was used with focus on the composition of the gut microbiota and its production of metabolites to evaluate the functionality. The fermentation kinetics, sugars, organic acids and inulin dosage in the fermented oat beverage were also evaluated. The acidification rate was 16.91 10⁻³ pH units.min⁻¹, reaching the final pH of 4.5 in 2.38 ± 0.05 h. Dosages of sucrose, glucose and lactic acid were 23.35 ± 0.45 g.L⁻¹, 21.37 ± 0.77 g.L⁻¹, 0.94 ± 0.05 g.L⁻¹, respectively. After simulated in vitro digestion, the inulin concentration was partially preserved with 20.11 ± 0.21 maltose equivalent (μg.mL⁻¹). The fermented and pre-digested oat beverage (with 7.71 ± 0.44 log CFU.mL⁻¹) was fed into TIM-2, which was previously inoculated with feces from healthy adults. The analysis identified nine bacterial taxa that were significantly modulated compared to the standard ileal effluent medium (SIEM) control. An increase in relative abundance of Lactobacillus and Catenibacterium, and reduction in Citrobacter, Escherichia-Shigella, and Klebsiella was observed. In addition, the cumulative means of short-chain fatty acids (SCFAs) increased, especially for acetate and butyrate. These findings suggest that the developed oat beverage can positively influence the gut microbiota and its activity, highlighting possible health benefits.