Li Dan, Li Jiaxi, Zhao Feng, Wang Guohong, Qin Qianqian, Hao Yanling
Key Laboratory of Functional Dairy, Co-constructed by Ministry of Education and Beijing Municipality, College of Food Science and Nutritional Engineering, China Agricultural University, 17 Qing Hua East Road, Hai Dian District, Beijing 100083, China.
Key Laboratory of Functional Dairy, Co-constructed by Ministry of Education and Beijing Municipality, College of Food Science and Nutritional Engineering, China Agricultural University, 17 Qing Hua East Road, Hai Dian District, Beijing 100083, China.
Food Chem. 2016 Apr 15;197(Pt A):367-72. doi: 10.1016/j.foodchem.2015.10.129. Epub 2015 Nov 10.
The yield of exopolysaccharide (EPS) produced by Streptococcus thermophilus 05-34 reached up to 250 mg/L under the optimal fermentation condition, which was 4.2-fold higher than that produced under the non-optimal fermentation condition. Structure analysis showed that EPS produced under the optimal fermentation condition was composed of galactose and glucose in a molar ratio of 1.0:0.8. This EPS was with a molecular mass of 4.7×10(5) Da, which was increased by 9 times compared with that in the non-optimal fermentation condition, while monosaccharide composition did not change. Furthermore, real-time quantitative PCR showed that the transcription level of epsC, which is responsible for chain-length determination, was up-regulated by 2.7-fold, suggesting that the increased molecular mass of EPS was resulted from improving polymerization degree of monosaccharide. These findings demonstrated that the optimized fermentation condition can improve EPS molecular mass, and may consequently modify the rheological properties of EPS.
在最佳发酵条件下，嗜热链球菌05 - 34产生的胞外多糖（EPS）产量高达250 mg/L，比非最佳发酵条件下的产量高4.2倍。结构分析表明，最佳发酵条件下产生的EPS由半乳糖和葡萄糖组成，摩尔比为1.0:0.8。该EPS的分子量为4.7×10(5) Da，与非最佳发酵条件下相比增加了9倍，而单糖组成没有变化。此外，实时定量PCR表明，负责链长测定的epsC的转录水平上调了2.7倍，这表明EPS分子量的增加是由于单糖聚合度提高所致。这些发现表明，优化的发酵条件可以提高EPS的分子量，并可能因此改变EPS的流变学性质。
