Abstract

Lactobacilli are able to produce exopolysaccharides (EPSs) with a wide diversity in structure and composition. However, changes in EPS production under environmental challenges are largely unknown. Here, to examine our hypothesis that EPS biosynthesis in lactobacilli is modulated by environmental conditions, we quantified and characterized the EPSs produced by Lactobacillus plantarum VAL6 following thermal stress and increased carbon dioxide (CO₂) concentration. We found that the EPS yield and composition of L. plantarum strain VAL6 were markedly affected by these treatment conditions. The highest EPS yield reached 17.32 g/L under CO₂ exposure, 2.2-fold higher compared to the control. The monosaccharide composition of synthesized EPSs was also altered when L. plantarum VAL6 was exposed to thermal stress and CO₂ concentration increase. Whereas proportion of mannose was lower, glucose and galactose contents were higher than those in non-stressed variants. Both increased CO₂ concentration and stress at 47°C enhanced the proportion of rhamnose in EPSs. Moreover, thermal stress and increased CO₂ concentration triggered the expression of the genes involved in EPS biosynthesis, e.g., glmU, pgmB1, epsE, epsF, wzx, and wzy. Furthermore, the expression of epsE and epsF resulted in an increase in the content of galactose and glucose in EPS monosaccharide composition.

中文翻译：

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通过施加热应力和增加二氧化碳浓度来提高植物乳杆菌 VAL6 胞外多糖的产生和单糖组成

摘要

乳酸杆菌能够产生结构和组成具有广泛多样性的胞外多糖 (EPS)。然而，环境挑战下 EPS 产量的变化在很大程度上是未知的。在这里，为了检验我们的假设，即乳酸杆菌中的 EPS 生物合成受环境条件调节，我们量化并表征了植物乳杆菌VAL6 在热应激和二氧化碳 (CO ₂ ) 浓度增加后产生的EPS 。我们发现植物乳杆菌VAL6 菌株的 EPS 产量和组成受这些处理条件的显着影响。CO ₂下EPS最高产量达到17.32 g/L暴露，比对照高 2.2 倍。当植物乳杆菌VAL6 暴露于热应力和 CO ₂浓度增加时，合成的EPS的单糖组成也发生了变化。而甘露糖的比例较低，葡萄糖和半乳糖的含量高于非应激变体。在 47°C 下增加的 CO ₂浓度和压力都增加了 EPS 中鼠李糖的比例。此外，热应激和增加的 CO ₂浓度触发了 EPS 生物合成相关基因的表达，例如glm U、pgm B1、eps E、eps F、wzx和wzy. 此外，eps E 和eps F的表达导致 EPS 单糖组成中半乳糖和葡萄糖含量的增加。