Production of canthaxanthin by extremely halophilic bacteria

Abstract

Soil samples from a salt farm were used as a source for the isolation of carotenoid-producing bacteria. The conditions for optimum growth and carotenoid production were established for the isolated bacteria. Carotenoids were analysed by spectrophotometry and High Performance Liquid Chromatography (HPLC). Thirty-one red extremely halophilic bacteria were isolated from saline soil samples collected from a salt farm in Alexandria, Egypt. Among the isolated strains, strain TM exhibited the highest carotenoid-producing ability. Maximum growth of strain TM occurred in the presence of high concentrations of sodium chloride and magnesium sulfate. Growth did not occur when NaCl concentration was lower than 10% and the cells lysed at this concentration. Optimum growth of and carotenoid production by strain TM were realized at 37°C in the presence of 1% yeast extract, 0.75% casamino acids, 25% NaCl, 4% MgSO 4, 0.2% KCl and at pH 7.2 with shaking for 6 d. Strain TM produced 2.06 mg total carotenoids g −1 dry cells, including 0.06 mg of β-carotene and 0.70 mg of canthaxanthin. This is the first report of an extremely halophilic bacterium that produces canthaxanthin.