title: The influence of fermentation condition on production and molecular mass of EPS produced by Streptococcus thermophilus 05-34 in milk-based medium.
abstract: 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.
authors.affiliation: 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.
authors.forename: Dan
authors.initials: D
authors.lastname: Li
authors.affiliation: 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.
authors.forename: Jiaxi
authors.initials: J
authors.lastname: Li
authors.affiliation: 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.
authors.forename: Feng
authors.initials: F
authors.lastname: Zhao
authors.affiliation: 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.
authors.forename: Guohong
authors.initials: G
authors.lastname: Wang
authors.affiliation: 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.
authors.forename: Qianqian
authors.initials: Q
authors.lastname: Qin
authors.affiliation: 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. Electronic address: haoyl@cau.edu.cn.
authors.forename: Yanling
authors.initials: Y
authors.lastname: Hao
mesh_terms: D000818:Animals; D002417:Cattle; D005285:Fermentation; D008892:Milk / Q000378:metabolism / Q000382:microbiology*; D008970:Molecular Weight; D011135:Polysaccharides, Bacterial / Q000737:chemistry* / Q000378:metabolism; D012212:Rheology; D048249:Streptococcus thermophilus / Q000737:chemistry / Q000378:metabolism*
chemical_list: D011135:Polysaccharides, Bacterial
keywords: Exopolysaccharide; Fermentation condition; Molecular mass; Streptococcus thermophilus; epsC expression