Characterization of halophilic C50 carotenoid-producing archaea isolated from solar saltworks in Bohai Bay, China

Abstract

Halophilic archaea comprise the majority of microorganisms found in hypersaline environments. C50 carotenoids accumulated in archaea cells are considered potential biotechnological products and possess a number of biological functions. Ten red colonies were isolated from brine water in a saltern crystallizer pond of the Hangu Saltworks, China. 16S rRNA gene sequence analysis showed that the colonies belonged to the extremely halophilic archaea genera Halobacterium and Halorubrum. Two representative strains, Halobacterium strain SP-2 and Halorubrum strain SP-4, were selected for further study on the phenotypic characteristics and effects of salinity and pH on accumulation and composition of pigments in their cells. The archaeal strains were isolated and grown in a culture medium prepared by dissolving yeast extract (10 g/L) and acid-hydrolyzed casein (7.5 g/L) into brine water obtained from a local salt pond. Their optimum salinity and pH for growth were 250 and 7, respectively, although pigment accumulation (OD490 / mL broth) was highest at pH 8. In addition, at 150–300 salinity, increasing salinity resulted in decreasing pigment accumulation. Analysis of the UV-Vis spectrum, TLC and HLPC chromatograms showed that C50 carotenoid bacterioruberin is the major pigment in both strains.