Probiotic properties of the 2-substituted (1,3)-beta-D-glucan-producing bacterium Pediococcus parvulus 2.6

Abstract

Exopolysaccharides have prebiotic potential and contribute to the rheology and texture of fermented foods. Here we have analyzed the in vitro bioavailability and immunomodulatory properties of the 2-substituted (1,3)-beta-D-glucan-producing bacterium Pediococcus parvulus 2.6. It resists gastrointestinal stress, adheres to Caco-2 cells, and induces the production of inflammation-related cytokines by polarized macrophages.

FIG. 1.

Detection of EPS production. The P. parvulus 2.6R (A) and 2.6NR (B) strains were subjected to agglutination tests and detection by phase-contrast microscopy. Left panels, bar = 100 μm; right panels, bar = 10 μm.

FIG. 2.

Analysis of cell survival after G and GI stresses. The indicated bacterial strains were left untreated (C) or subjected to various G or GI stresses as described in the text. After staining, cell viability was analyzed by measurement of green and red fluorescence. The values are the means for three independent experiments and are expressed as percentages of the green/red (G/R) fluorescence ratio for untreated control samples. The 100% control values for untreated 2.6R and 2.6NR were 10.05 and 9.98, respectively.

FIG. 3.

Adhesion of bacterial strains to Caco-2 cells. Adhesion levels are expressed as percentages of the total number of bacteria (adhered plus unadhered) detected after exposure to Caco-2 cells for 1 h. Each adhesion assay was conducted in triplicate. The values are the means for three independent experiments in which three independent determinations were performed. (Insets) Prior to the adhesion experiments, bacteria were analyzed in a JEOL 1230 transmission electron microscope operated at 100 kV.

FIG. 4.

Cytokine responses of macrophages to P. parvulus strains. M1 and M2 macrophages were either left untreated (basal 18 h) or stimulated with lipopolysaccharide (LPS) from Escherichia coli O55:B5 (Sigma, Barcelona, Spain) at 10 ng ml⁻¹, P. parvulus 2.6 (2.6R), or its nonropy mutant (2.6NR), and the levels of TNF-α (A), IL-8 (B), and IL-10 (C) released were determined. Each determination was performed in triplicate, and the means and standard deviations are shown.