Abstract

The production of ectoine from a halophilic bacteria Halomonas elongata BK-AG25 was optimized using osmotic shock technique. At first, the bacteria were grown in MM63 media containing optimal level of salt to gain high biomass yield. The bacteria were than inoculated in the same media with high concentration of salt (osmotic upshock) to produce ectoine. Subsequently, the bacteria were transferred into distilled water containing lower concentration of salt (osmotic downshock) to release ectoine produced. The two process is known as “bacterial milking”. These process were repeated several cycles to gain a maximum yield of ectoine. The survival of the cells and ectoine released by the bacteria after osmotic downshock were determined. The results showed that the survival bacteria were more than 70% after the serial osmotic downshock, which was from 17.5%(w/v) to 1.5%(w/v) and then to 3% (w/v) NaCl. However, only 9% of the bacteria were survive when the same process was occurred from 17.5% to 0% (w/v) NaCl. By using the former downshock process, the yield of ectoine released by the bacteria was relatively high, which was about 88%. The productivity of the bacteria in producing ectoine was high, which was about 206.4 mg extracellular per g cell dry weight.

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