ABSTRACT
The carotenogenic microalga Dunaliella salina is cultivated as a natural source of ¾-carotene. The 9-cis isomer of ¾-carotene is found only in natural sources having commercial advantages over the all-trans isomer due to its high liposolubility and antioxidant power. High irradiance appears to stimulate specifically all-trans ¾-carotene accumulationin D. salina, whereas low temperature apparently elicits ¾-carotene and 9-cis ¾-carotene production. We studied the effect of temperature and irradiance on the growth and the carotenogenesis of three Chilean (CONC-001, CONC-006 and CONC-007) and four non-Chilean (from Mexico, China, Australia and Israel) strains of D. salina cultivated under two photon flux densities (40 and 110 _ 6mol photons.m-2.s-1) and two temperatures (15 and 26ùª C). The Chilean strain CONC-001 and all of the non-Chilean strains exhibited the highest growth rates and the maximum cell densities, whereas the Chilean strains CONC-006 and CONC-007 showed the lowest values in both parameters. The Australian strain showed the highest accumulation of total carotenoids per unit volume (40.7 mg.L-1), whereas the Chilean strains CONC-006 and CONC-007, the only ones isolated from Andean environments, yielded the highest amounts of carotenoids per cell (61.1 and 92.4 pg.cell_1, respectively). Temperature was found to be more effective than irradiance in changing the qualitative and quantitative carotenoids composition. The Chilean strains accumulated 3.5-fold more ¾-carotene than the non-Chilean strains when exposed to 15ùª C and, unlike the non-Chilean strains, also accumulated this pigment at 26ùª C. The 9-cis/all-trans ¾-carotene ratio was > 1.0 in all treatments for all strains, and the values were not greatly influenced by either temperature or photon flux density. Physiological and biotechnological implications of these results are discussed.