Purification, Preliminary Structure and Antitumor Activity of Exopolysaccharide Produced by Streptococcus thermophilus CH9
2018
Naxin Sun | Huiping Liu | Shaojuan Liu | Xinyuan Zhang | Pei Chen | Weihong Li | Xiangxin Xu | Wentan Tian
In the present study, the preliminary structure and in vitro antitumor activity of three exopolysaccharides (EPSs) from Streptococcus thermophilus CH9 were investigated. Then, three purified fractions of EPS-1a, EPS-2a, and EPS-3a were obtained by chromatography using DEAE-52 cellulose and Sephadex G-100, respectively. The average molecular weight of EPS-1a, EPS-2a, and EPS-3a, were 1.80 ×: 106, 1.06 ×: 106 and 1.05 ×: 106. The monosaccharide composition of EPS-3a was dramatically different from the others. The EPS-1a and EPS-2a were mainly composed of mannose, in a ratio of 69.82% and 57.09%, respectively, while EPS-3a was mainly composed of glucose (63.93%), without mannose. In addition, the surface morphology observed suggested that there were protein particles on the sugar chain of EPS-3a and EPS-3a was a protein-containing polysaccharide. Furthermore, EPS-3a exhibited higher antitumor activity against human liver cancer HepG2 cells in vitro. The antitumor activity of EPS-3a in HepG2 cells was associated with cell apoptosis. HE staining and Hoechst 33342 staining showed that with the treatment of EPS-3a, HepG2 cells had typical morphological changes. Flow cytometry analysis showed that the cell cycle was arrested at G0/G1 phase.
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