Extending viability of Lactobacillus plantarum and Lactobacillus johnsonii by microencapsulation in alginate microgels.

AIM: To investigate whether microencapsulation of Lactobacillus in alginate microbeads will lead to increased longevity during refrigerated storage or simulated digestion. MATERIALS AND METHODS: Microscopy was used to confirm that Lactobacillus plantarum ATCC BAA-793 and Lactobacillus johnsonii ATCC 33200 were immobilised within the microbeads and laser scattering analysis was used to determine the mean diameter of the microbeads. The number of viable cells were enumerated throughout refrigerated storage and simulated digestion experiments. RESULTS: Microencapsulation was shown to have differing effects on viability depending on the species, but led to extended viability during refrigerated storage and simulated digestion in L. johnsonii and L. plantarum respectively. CONCLUSION: Fermented functional foods contain microbes beneficial to human health. However, extended shelf storage and the harsh environment of the GI tract significantly reduces the number of viable microbes reaching the consumer. Microencapsulation allows beneficial microbes to reach the gut of the consumer in higher numbers, and thus confer greater health benefits.

EpsA is an essential gene in exopolysaccharide production in Lactobacillus johnsonii FI9785.

Lactobacillus johnsonii FI9785 has an eps gene cluster which is required for the biosynthesis of homopolymeric exopolysaccharides (EPS)-1 and heteropolymeric EPS-2 as a capsular layer. The first gene of the cluster, epsA, is the putative transcriptional regulator. In this study we showed the crucial role of epsA in EPS biosynthesis by demonstrating that deletion of epsA resulted in complete loss of both EPS-1 and EPS-2 on the cell surface. Plasmid complementation of the epsA gene fully restored EPS production, as confirmed by transmission electron microscopy and nuclear magnetic resonance (NMR) analysis. Furthermore, this complementation resulted in a twofold increase in the expression levels of this gene, which almost doubled amounts of EPS production in comparison with the wild-type strain. Analysis of EPS by NMR showed an increased ratio of the heteropolysaccharide to homopolysaccharide in the complemented strain and allowed identification of the acetylated residue in EPS-2 as the (1,4)-linked ßGlcp unit, with the acetyl group located at O-6. These findings indicate that epsA is a positive regulator of EPS production and that EPS production can be manipulated by altering its expression.