Barley β-glucans-containing food enhances probiotic performances of beneficial bacteria

Abstract

Currently, the majority of prebiotics in the market are derived from non-digestible oligosaccharides. Very few studies have focused on non-digestible long chain complex polysaccharides in relation to their potential as novel prebiotics. Cereals β-glucans have been investigated for immune-modulating properties and beneficial effects on obesity, cardiovascular diseases, diabetes, and cholesterol levels. Moreover, β-glucans have been reported to be highly fermentable by the intestinal microbiota in the caecum and colon, and can enhance both growth rate and lactic acid production of microbes isolated from the human intestine. In this work, we report the effects of food matrices containing barley β-glucans on growth and probiotic features of four Lactobacillus strains. Such matrices were able to improve the growth rate of the tested bacteria both in unstressed conditions and, importantly, after exposure to in vitro simulation of the digestive tract. Moreover, the effect of β-glucans-containing food on bacterial adhesion to enterocyte-like cells was analyzed and a positive influence on probiotic-enterocyte interaction was observed.

Figure 1.

Growth curves of L. plantarum WCFS1, L. acidophilus LA5, L. plantarum CETC 8328 and L. fermentum CECT 8448. Bacteria were grown in MRS and MRS supplemented with different food matrices (not-enriched pasta, β-glucans enriched pasta and barley flour). Values represent mean ± standard deviation of three different experiments. Statistical analysis was carried out by Student’s t-test and significant differences are relative to MRS (positive control). ^a p < 0.005 for samples cultivated in MRS supplemented with β-glucans enriched pasta; ^b p < 0.005 for samples cultivated in MRS supplemented with barley flour; ^c p < 0.005 for samples cultivated in MRS supplemented with not-enriched pasta.

Figure 2.

Percentage of cell survival after in vitro oro-gastrointestinal tract simulation, including oral ■, gastric (pH 2.0 and pH 3.0 ), and intestinal (small and large intestine □) stresses conveying microorganisms in saline solution (negative control) and three different food matrices (not-enriched pasta; β-glucans enriched pasta; barley flour). Values represent mean ± standard deviation of three different experiments. Statistical analysis was carried out by Student’s t-test (* p < 0.05 and ** p < 0.005) and significant differences are relative to OGI transit using saline solution as a carrier. Cell survival is expressed as a percentage (in logarithmic scale) relative to the untreated control sample (1.00 × 10² corresponds to 100%, 1.00 × 10⁶ corresponds to 0.000001%).

Figure 3.

Growth curves of L. plantarum WCFS1, L. acidophilus LA5, L. plantarum CETC 8328 and L. fermentum CECT 8448, grown in MRS after exposure to oro-gastrointestinal stresses using saline solution and different food matrix (not-enriched pasta, β-glucans enriched pasta and barley flour). Values represent mean ± standard deviation of three different experiments. Statistical analysis (data not shown) was carried out by Student’s t-test (see Results and Discussion section).

Figure 4.

Adhesion of L. plantarum WCFS1, L. acidophilus LA5, L. plantarum CETC 8328 and L. fermentum CECT 8448 to Caco-2 cells in the presence of DMEM medium (positive control), not-enriched pasta, β-glucans enriched pasta and barley flour. Values represent mean ± standard deviation of three different experiments.