Ectoine Synthesis and Release Under Osmotic Shock in Halomonas venusta DSM4743

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”.