Lactobacillus kefiranofaciens and Lactobacillus satsumensis isolated from Brazilian kefir grains produce alpha-glucans that are potentially suitable for food applications

Lactic acid bacteria produce exopolysaccharides, which have broad application in the food industry, especially as thickeners, stabilizers, and gelling agents. Additionally, some biopolymers have been regarded as health promoters due to their role as prebiotics and their immunomodulatory properties. This study aimed to characterize three exopolysaccharides produced by novel Lactobacillus strains from Brazilian milk or sugar water kefir and to determine their biocompatibility. Lactobacillus kefiranofaciens 1P3 and Lactobacillus satsumensis 10P and 10P2 were grown in the presence of sucrose, and their exopolysaccharides were purified and structurally elucidated. Glucose was the only sugar found in the polysaccharide chains, so most of the glucose residues were linked by α-(1,6) glycosidic bonds (∼90%) and the estimated molecular weight was 800 kDa. According to the NIR spectra, α-glucan 1P3, 10P, and 10P2 were all different compounds. The in vitro cytotoxicity of the polymers was low or nonexistent, especially in nontumor cells. The polymers had no significant effects on the expression of proinflammatory and regulatory cytokines in the intestine of mice. In contrast, the intestinal IgA+ B cells were significantly higher. Taken together, this study suggests that these exopolysaccharides might be useful as food additives due to their safety features to the host. •Brazilian kefir grains are important source of exopolysaccharide producing lactobacilli.•Three different α-(1,3) branched α-(1,6) glucans were chemically characterized.•The α-glucans demonstrated no cytotoxicity to tumoral and non-tumoral cells.•IgA producing cells were stimulated in mice small intestine after oral α-glucan treatment during seven days.•Alpha-glucan treatment led low or no difference on expression of some cytokines on mice small intestine.