Graduate University of Sciences and Technology, Vietnam Academy of Science and Technology, Hanoi, Vietnam.
An Giang University, Vietnam National University, Ho Chi Minh City, Vietnam.
Sci Rep. 2021 Jan 14;11(1):1301. doi: 10.1038/s41598-020-80634-1.
To investigate the effect of environmental stresses on the exopolysaccharide biosynthesis, after 24 h of culture at 37 °C with pH 6.8 and without sodium chloride, Lactobacillus plantarum VAL6 was exposed to different stress conditions, including pH (pHs of 3 and 8) and high sodium chloride concentration treatments. The results found that Lactobacillus plantarum VAL6 exposed to stress at pH 3 for 3 h gives the highest exopolysaccharide yield (50.44 g/L) which is 6.4 fold higher than non-stress. Under pH and sodium chloride stresses, the mannose content in exopolysaccharides decreased while the glucose increased in comparison with non-stress condition. The galactose content was highest under stress condition of pH 8 meantime rhamnose content increased sharply when Lactobacillus plantarum VAL6 was stressed at pH 3. The arabinose content in exopolysaccharides was not detected under non-stress condition but it was recorded in great amounts after 3 h of stress at pH 3. In addition, stress of pH 8 triggered the mRNA expression of epsF gene resulting in galactose-rich EPS synthesis. According to our results, the stresses of pH and sodium chloride enhance the production and change the mRNA expression of epsF gene, leading to differences in the monosaccharide composition of exopolysaccharides.
为了研究环境应激对胞外多糖生物合成的影响，在 37°C、pH6.8、无氯化钠的条件下培养 24 小时后，将植物乳杆菌 VAL6 暴露于不同的应激条件下，包括 pH（3 和 8）和高氯化钠浓度处理。结果发现，植物乳杆菌 VAL6 在 pH3 下应激 3 小时产生的胞外多糖产量最高（50.44g/L），比非应激条件下高 6.4 倍。在 pH 和氯化钠应激下，与非应激条件相比，胞外多糖中的甘露糖含量降低，葡萄糖含量增加。在 pH8 的应激条件下，半乳糖含量最高，而当植物乳杆菌 VAL6 在 pH3 下应激时，鼠李糖含量急剧增加。在非应激条件下未检测到胞外多糖中的阿拉伯糖，但在 pH3 应激 3 小时后大量存在。此外，pH8 的应激触发了 epsF 基因的 mRNA 表达，导致富含半乳糖的 EPS 合成。根据我们的结果，pH 和氯化钠的应激增强了胞外多糖的产生，并改变了 epsF 基因的 mRNA 表达，导致胞外多糖中单糖组成的差异。
