Key Lab of Dairy Biotechnology and Safety Control, Yangzhou University, Yangzhou, 225127, Jiangsu Province, China.
College of Food Science and Engineering, Yangzhou University, Yangzhou, 225127, Jiangsu Province, China.
Curr Microbiol. 2023 Aug 27;80(10):331. doi: 10.1007/s00284-023-03421-x.
The free exopolysaccharide (f-EPS) produced by Streptococcus thermophilus is a natural texture modifier with health-promoting properties and has thus become one of the most interesting metabolites for researchers. The present work aimed to further understand the nutritional requirements for the growth of and the f-EPS production by S. thermophilus. The types and concentrations of compounds in the complete chemically defined medium were changed in turn to evaluate the effects of single nutrients on the growth of and f-EPS production by S. thermophilus 937. The results showed that cysteine, glutamine, histidine, methionine, tryptophan, tyrosine, leucine, isoleucine, and valine played an important role in maintaining the rapid and stable growth of S. thermophilus 937. S. thermophilus 937 also required calcium pantothenate, niacin, pyridoxine, riboflavin, and thiamine hydrochloride as essential nutrients for growth. Increases in the concentrations of lactose, glutamate, histidine, or isoleucine significantly increased the production of free exopolysaccharide by S. thermophilus 937, and when the lactose concentration increased to 20 g·L and the concentration of the three-amino-acid combination increased to 15 mM, the f-EPS yield increased to a maximum of 35.34 μg·mL. This finding indicated that lactose and the 3 amino acids exert synergistic effects on the promotion of f-EPS production. In addition, lactose and the three amino acids have strain specific promoting effects on f-EPS production by S. thermophilus. This study provides a further understanding of the effects of nutrients on the biosynthesis of f-EPS by S. thermophilus.
嗜热链球菌产生的游离胞外多糖（f-EPS）是一种具有促进健康特性的天然质构改良剂，因此成为研究人员最感兴趣的代谢物之一。本工作旨在进一步了解嗜热链球菌生长和 f-EPS 生产的营养需求。依次改变完全化学定义培养基中的化合物类型和浓度，以评估单一营养物质对嗜热链球菌 937 生长和 f-EPS 生产的影响。结果表明，半胱氨酸、谷氨酰胺、组氨酸、蛋氨酸、色氨酸、酪氨酸、亮氨酸、异亮氨酸和缬氨酸对维持嗜热链球菌 937 的快速和稳定生长起着重要作用。嗜热链球菌 937 还需要泛酸钙、烟酸、吡哆醇、核黄素和盐酸硫胺素作为生长所必需的营养物质。乳糖、谷氨酸、组氨酸或异亮氨酸浓度的增加显著提高了嗜热链球菌 937 游离胞外多糖的产量，当乳糖浓度增加到 20 g·L 且三种氨基酸混合物的浓度增加到 15 mM 时，f-EPS 的产量增加到最大值 35.34 μg·mL。这一发现表明，乳糖和三种氨基酸对促进 f-EPS 生产具有协同作用。此外，乳糖和三种氨基酸对嗜热链球菌 f-EPS 的生产具有菌株特异性促进作用。本研究进一步了解了营养物质对嗜热链球菌 f-EPS 生物合成的影响。
