Influence of casein hydrolysates on exopolysaccharide synthesis by Streptococcus thermophilus and Lactobacillus delbrueckii ssp. bulgaricus

Qingli Zhang, Bao Yang, Mindy M. Brashears, Zhimin Yu, Mouming Zhao, Ning Liu, Yinjuan Li

Research output: Contribution to journalArticle

8 Scopus citations

Abstract

BACKGROUND: A lot of interesting research has been undertaken to enhance the yield of exopolysaccharides (EPS) produced by lactic acid bacteria (LAB). The objective of this study was to determine the influence of casein hydrolysates (CH) with molecular weight less than 3 kDa on cell viability, EPS synthesis and the enzyme activity involved in EPS synthesis during the co-culturing of Streptococcus thermophilus and Lactobacillus delbrueckii ssp. bulgaricus in MRS broth for 72 h at 37±0.1 °C. RESULTS: The highest EPS yield (150.1 mg L-1) was obtained on CH prepared with papain (CHP) at 48 h. At 24 h, EPS were composed of galactose, glucose and rhamnose in a molar ratio of 1.0:2.4:1.5. The monosaccharide composition changed with extension of the fermentation time. The activities of α-phosphoglucomutase, uridine 5'-diphosphate (UDP)-glucose pyrophosphorylase and UDP-galactose 4-epimerase were associated with EPS synthesis. Moreover, the activities of β-phosphoglucomutase and deoxythymadine 5'-diphosphate (dTDP)-glucose pyrophosphorylase involved in rhamnose synthesis were very low at the exponential growth phase and could not be detected during other given periods. CONCLUSION: The influence of different CH (<3 kDa) on LAB viability, EPS production, EPS monomeric composition and activity levels of key metabolic enzymes was distinct. Besides, their influence was related to the distribution of amino acids.

Original languageEnglish
Pages (from-to)1366-1372
Number of pages7
JournalJournal of the Science of Food and Agriculture
Volume94
Issue number7
DOIs
StatePublished - May 2014

Keywords

  • Casein hydrolysates
  • EPS biosynthesis
  • Enzyme activity
  • Exopolysaccharides
  • Lactic acid bacteria

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