Saccharomyces cerevisiae EC-1118 enhances the survivability of probiotic Lactobacillus rhamnosus HN001 in an acidic environment

Abstract

The present study attempted to partially characterize and elucidate the viability-enhancing effect of a yeast strain Saccharomyces cerevisiae EC-1118 on a probiotic strain Lactobacillus rhamnosus HN001 under acidic conditions using a model system (non-growing cells). The yeast was found to significantly enhance (P < 0.05) the viability of the probiotic strain under acidic conditions (pH 2.5 to 4.0) by 2 to 4 log cycles, and the viability-enhancing effects were observed to be influenced by pH, and probiotic and yeast concentrations. Microscopic observation and co-aggregation assay revealed that the viability-enhancing effect of the yeast could be attributed to direct cell-cell contact co-aggregation mediated by yeast cell surface and/or cell wall components or metabolites. Furthermore, non-viable yeast cells killed by thermal means were observed to enhance the viability of the probiotic strain as well, suggesting that the surface and/or cell wall component(s) of the yeast contributing to co-aggregation was heat-stable. Cell-free yeast supernatant was also found to enhance the viability of the probiotic strain, indicating the presence of protective yeast metabolite(s) in the supernatant. These findings laid the foundation for further understanding of the mechanism(s) involved and for developing novel microbial starter cultures possibly without the use of live yeast for ambient-stable high-moisture probiotic foods.

Influence of commercial inactivated yeast derivatives on the survival of probiotic bacterium Lactobacillus rhamnosus HN001 in an acidic environment

“…Therefore, the objective of this pilot study was to investigate the influence of three commercial IYDs that are rich in yeast parietal molecules on the survival of a widely used probiotic bacteria strain, Lactobacillus rhamnosus HN001, in a simulated acidic environment (buffer). As the IYDs studied are derived from S. cerevisiae of oenological origin, the findings of this study could also shed light on the survival-enhancing properties of non-viable S. cerevisiae EC-1118 cells on L. rhamnosus HN001 as previously reported by Suharja et al (2014) and Lim et al (2015). …”

“…An acid stress assay, modified from the method of Lim et al (2015), was used to assess the impact of IYDs on the survival of L. rhamnosus HN001 in an acidic buffer. Twenty mL of L. rhamnosus HN001 working culture was mixed with an equal volume of IYD extract (giving a final IYD concentration of 3 g/L or 0.3% (w/v)) or pH 3.0 PBS for the control in a 50-mL polypropylene centrifuge tube and incubated statically in a 30 °C incubator for 10 h. As viable S. cerevisiae EC-1118 cells were demonstrated to enhance the viability of L. rhamnosus HN001 under similar stress conditions, an assay comprising of equal volumes probiotic bacteria and yeast working cultures was also performed for comparing the IYDs’ probiotic viability enhancing effect (Lim et al 2015).…”

“…Twenty mL of L. rhamnosus HN001 working culture was mixed with an equal volume of IYD extract (giving a final IYD concentration of 3 g/L or 0.3% (w/v)) or pH 3.0 PBS for the control in a 50-mL polypropylene centrifuge tube and incubated statically in a 30 °C incubator for 10 h. As viable S. cerevisiae EC-1118 cells were demonstrated to enhance the viability of L. rhamnosus HN001 under similar stress conditions, an assay comprising of equal volumes probiotic bacteria and yeast working cultures was also performed for comparing the IYDs’ probiotic viability enhancing effect (Lim et al 2015). An 1-mL aliquot was withdrawn every 2 h from the probiotic cell suspensions and serially diluted with 0.1% w/v buffered peptone water (Merck) for the enumeration of viable microbial counts.…”

“…Recent studies have also demonstrated improvements in probiotic acid tolerance brought about by the application of autoclaved whole yeast cells and yeast cell wall polysaccharides (Ganan et al 2012; Lim et al 2015; Rosburg et al 2010). These polysaccharides are mainly β-glucans and mannans from mannoproteins, constituting approximately 60 and 40% of yeast cell wall dry mass, respectively (Aguilar et al 2012).…”

Probiotic: effectiveness nutrition in cancer treatment and prevention

“…has inhibitory activity against Streptococcus mutans, and Streptococcus sobrinus, etiological agents strongly associated with dental cavities in humans (112). Lim et al (2015) showed that some yeast increase the growth of other probiotics under acidic conditions, like Saccharomyces cerevisiae CE-1118, that improves the viability of the probiotic Lactobacillus rhamnosus HN001 under pH 2.5-4 (113).…”