title: The effect of temperature and irradiance on the growth and carotenogenic capacity of seven strains of Dunaliella salina (Chlorophyta) cultivated under laboratory conditions.
abstract: The carotenogenic microalga Dunaliella salina is cultivated as a natural source of beta-carotene. The 9-cis isomer of beta-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 beta-carotene accumulation in D. salina, whereas low temperature apparently elicits a-carotene and 9-cis betacarotene 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 micromol photons x m(-2) x s(-1)) and two temperatures (15 and 26 degrees 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 x 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 x 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 alpha-carotene than the non-Chilean strains when exposed to 15 degrees C and, unlike the non-Chilean strains, also accumulated this pigment at 26 degrees C. The 9-cis/all-trans beta-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.
authors.affiliation: Laboratorio de Ficolog'ia, Departamento de Botánica, Facultad de Ciencias Naturales y Oceanográficas, Universidad de Concepción, Concepción, Chile. pgomez@udec.cl
authors.forename: Patricia I
authors.initials: PI
authors.lastname: Gómez
authors.forename: Mariela A
authors.initials: MA
authors.lastname: González
mesh_terms: D000704:Analysis of Variance; D002338:Carotenoids / Q000096:biosynthesis*; D000460:Chlorophyta / Q000254:growth & development* / Q000378:metabolism / Q000528:radiation effects; D007753:Laboratories; D013696:Temperature; D013997:Time Factors; D019207:beta Carotene / Q000096:biosynthesis*
chemical_list: D019207:beta Carotene; D002338:Carotenoids; C041635:alpha-carotene