期刊
FRONTIERS IN MICROBIOLOGY
卷 12, 期 -, 页码 -出版社
FRONTIERS MEDIA SA
DOI: 10.3389/fmicb.2021.696222
关键词
Streptococcus thermophilus; EpsC; homologous expression; molecular weight; yogurt; viscoelasticity
类别
资金
- National Key Research and Development Program of China [2018YFC1604303]
- National Natural Science Foundation of China [21476250]
Homologous over-expression of EpsC in Streptococcus thermophilus can increase the molecular weight of EPS and improve the microrheological or physical properties of yogurt.
In Streptococcus thermophilus, EpsC is a polysaccharide co-polymerase which is involved in determining the chain length of EPS synthesized by the Wzx/Wzy-dependent pathway. Our previous study found that there was a positive correlation between transcription level of epsC and molecular weight of EPS in S. thermophilus 05-34. To further investigate the effects of EpsC on EPS biosynthesis, this gene was over-expressed in S. thermophilus 05-34 in this study. Reverse transcription qPCR and Western blotting confirmed the successful transcription and translation of epsC in 05-34, respectively. The yield of EPS was not affected by the over-expression of EpsC. Gas chromatography-mass spectrometry (GC-MS) showed that the monosaccharide composition was still composed of galactose and glucose in a molar ratio of 1.0:0.8, whereas high performance gel permeation chromatography (HPGPC) indicated that the molecular weight of EPS was increased from 4.62 x 10(5) Da to 9.17 x 10(5) Da by the over-expression of EpsC. In addition, S. thermophilus 05epsC which could produce higher molecular weight EPS improved the viscoelasticity and water-holding capacity of yogurt, but significantly reduced the level of syneresis in yogurt. In summary, these results indicated that homologous over-expression of EpsC in S. thermophilus could increase the molecular weight of EPS and improve the microrheological or physical properties of yogurt.
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