Halomonas venusta DSM4743渗透压冲击下四氢嘧啶合成与释放

Ectoine Synthesis and Release Under Osmotic Shock in Halomonas venusta DSM4743

摘要:

选择耐受较高NaCl浓度, 而且四氢嘧啶胞内浓度阈值较高的菌株, 研究其四氢嘧啶发酵条件和工艺, 对于提高四氢嘧啶的制备效率具有实际意义。考察了碳源、NaCl浓度、酵母膏添加量对Halomonas venusta DSM4743四氢嘧啶合成的影响, 考察了优化条件下的四氢嘧啶分批发酵进程, 并利用“细菌挤奶”工艺制备四氢嘧啶。结果表明: 谷氨酸单钠为唯一碳氮源、NaCl浓度为1.5 mol/L、酵母膏添加量为0.5%的条件有利于四氢嘧啶合成。在优化条件下10 L发酵罐分批发酵, 四氢嘧啶最大合成量为3.2 g/L, 合成效率为2.7 g/(L·d)。通过“细菌挤奶”工艺制备四氢嘧啶, 6个渗透压冲击循环后, 四氢嘧啶总合成量为14.7 g/L, 总释放量为14.3 g/L, 平均释放率为97%, 合成效率2.1 g/(L·d)。中度嗜盐菌Halomonas venusta DSM4743耐受较高浓度的NaCl, 而且四氢嘧啶胞内浓度阈值较高, 优化的发酵条件及“细菌挤奶”工艺, 获得了较高的四氢嘧啶制备效率。

关键词:中度嗜盐菌, Halomonas venusta DSM4743, 四氢嘧啶, 细菌挤奶, 渗透压冲击

Abstract:

In order to improve the productivity of Ectoine, the strain which could resist to higher halostress of NaCl concentration and synthesize higher intracellular Ectoine concentration was adopted. The fermentation conditions and processes of Ectoine were assessed. The impacts of carbon source and concentration of NaCl and yeast extract on the synthesizing Ectoine with Halomonas venusta DSM4743 were investigated. The batch fermentation processe of Ectoine was investigated under the optimum conditions and the Ectoine was produced by “bacterial milking”. As the results showed, the amount of synthesized Ectoine could be enhanced when the medium adopted monosodium glutamate as the sole source of carbon and nitrogen, and at the same time in 1.5 mol/L NaCl and 0.5% yeast extract. Under optimal conditions, batch fermentations were performed in a 10-liter fermentor. The maximum Ectoine concentration and the Ectoine productivity were 3.2 g/L and 2.7 g/(L·d), respectively. Ectoine was produced by Halomonas venusta DSM4743 with “bacterial milking”. The total concentration of synthesized and released Ectoine were 14.7 g/L and 14.3 g/L, respectively. The average release rate of Ectoine was 97% and the Ectoine productivity was 2.1 g/(L·d) after six cycles of osmotic shock. Moderately halophilic bacterial strain Halomonas venusta DSM4743 was tolerant to higher NaCl concentrations and had the higher threshold of intracellular Ectoine concentration. The higher Ectoine productivity was obtained with the optimization of fermentation conditions and “bacterial milking”.

Key words:Moderately halophilic bacterial strain, Halomonas venusta DSM4743, Ectoine, Bacterial milking, Osmotic shock