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Sialic acid is a class of neuraminidase derivatives, widely present in animal tissues and microorganisms, is an important part of the cell membrane protein involved in a variety of physiological functions of the cell surface, play a very important to regulate the body's physiological, biochemical functions role. Poly sialic acid, sialic acid monomer to α-2, 8 or α-2, 9 glycosidic linkage linear homopolymer is the main component of the capsular polysaccharide in a few bacteria. Through microbial synthesis of poly sialic acid, and then hydrolysis monomer sialic acid is one of the main methods of sialic acid production. Firstly polysialic acid synthesis of precursor substances - sodium pyruvate E. coli CCTCC M208088 synthesis of polysialic acid. We found that the sodium pyruvate, the amount of additive and adding time of polysialic acid synthesis yields a significant effect. Polysialic acid synthesis efficiency To maximize strengthen the paper from a shake flask level optimization the sodium pyruvate add strategy: the initial stage of fermentation, add 6 g / L sodium pyruvate, can promote poly saliva acid synthesis, its final production reached 3470 mg / L, compared to 73% control. Verify the policy in a 30 L fermentor level polysialic acid production reached 6630 mg / L, compared to 53% control. In addition, we investigated in shake flask level oxygen free radical stress E. coli CCTCC M208088 synthesis of polysialic acid. H 2 O 2 can effectively stimulate the synthesis of polysialic acid and H2O2 added time, the amount of additives, and add significant synthesis of polysialic acid. Further optimization experiments show that, in the the polysialic acid fermentation process, using the three-point addition method (4 h 4.0 mmol / L (final concentration) for 8 h 8.0 mmol / L (final concentration), 12 h 16.0 mmol / L (final concentration)) the best polysialic acid yield reached 2705 mg / L, a 35% increase compared with the control. This policy in a 30 L fermentor level verification, polysialic acid production reached 5504 mg / L, a 27% increase compared with the control. Finally, in achieving efficient synthesis of polysialic acid on the basis, the improved polysialic acid hydrolysis of sialic acid process. Were optimized of polysialic acid hydrolysis method, and purification of sialic acid monomer various methods were studied and compared, and finalized by the of polysialic acid preparation sialic acid monomer process: polysialic acid dissolved in 0.05 mol / L H 2 SO 4 solution, 80 ℃ water bath to maintain 4 h. The hydrolyzate added directly to the 5-fold volume of glacial acetic acid, and then 4 ° C stand for 3 days, and suction filtered to remove glacial acetic acid, i.e. a sialic crystal, and then washed with glacial acetic acid crystals, the degree of vacuum of 50 ℃ 0.095 MPa under conditions maintained for 4 h, which was the final product, and a purity of more than 95% of sialic acid obtained by this process.
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