Effect of Complex Nutrients and Repeated-Batch Cultivation of Halobacterium salinarum on enhancing Bacteriorhodopsin Production

Abstract

The extreme halophilic bacteria Halobacterium salinarum is known to produce bacteriorhodopsin (BR) protein in its purple membrane (PM) as a light-driven pump for the synthesis ATP. Its growth does not utilize simple carbon sources such as glucose, but relies on the complex carbon/nitrogen sources. The production yield of BR in the culture of H. salinarum also strongly depends on the complex nitrogen sources employed. From the various complex carbon/nitrogen sources employed in this work, tryptone rather than commonly used peptone was found to be the best complex nutrient for the growth of H. salinarum and its BR production. Bubble column photobioreactor operated in a repeated-batch mode was also employed to enhance the growth of H. salinarum by intermittent removing growth inhibitory metabolites. By employing 0.5% tryptone as carbon/nitrogen source in the culture medium, 201.8 mg/L of BR was obtained after 210 h repeated-batch cultivation which is about 50% higher than that obtained in shaker flask cultivation.