Lim Phebe Lixuan, Toh Mingzhan, Liu Shao Quan
Food Science and Technology Programme, Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore, 117543, Singapore.
Appl Microbiol Biotechnol. 2015 Aug;99(16):6803-11. doi: 10.1007/s00253-015-6560-y. Epub 2015 Apr 7.
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.
本研究试图利用模型系统（非生长细胞），部分表征并阐明酵母菌株酿酒酵母EC - 1118在酸性条件下对益生菌鼠李糖乳杆菌HN001的活力增强作用。研究发现，在酸性条件（pH 2.5至4.0）下，该酵母能显著提高（P < 0.05）益生菌菌株的活力，提高幅度为2至4个对数循环，且活力增强效果受pH值、益生菌和酵母浓度的影响。显微镜观察和共聚集分析表明，酵母的活力增强作用可归因于酵母细胞表面和/或细胞壁成分或代谢产物介导的直接细胞间接触共聚集。此外，还观察到经热灭活的无活力酵母细胞也能提高益生菌菌株的活力，这表明酵母中有助于共聚集的表面和/或细胞壁成分具有热稳定性。无细胞酵母上清液也能提高益生菌菌株的活力，表明上清液中存在具有保护作用的酵母代谢产物。这些发现为进一步理解其中涉及的机制以及开发可能无需使用活酵母的新型微生物发酵剂奠定了基础，用于环境稳定的高水分益生菌食品。
