Effects of salinity increase on carotenoid accumulation in the green alga Dunaliella salina

Abstract

The effect of sudden salinity increases on the kinetics of growth and carotenogenesis was studied in three geographically diverse isolates of Dunaliella salina. A sudden increase in salinity results in a lag phase in growth and the length of this lag phase is dependent on the final salinity and the magnitude of the salinity change (no lag at 10-15% w/v NaCI, 4-day lag at 30% NaCl). There is also a lag before an increase in the total carotenoid content can be measured following the salinity up-shock, and the length of the lag depends largely on the initial salinity and the magnitude of the salinity up-shock, whereas the rate of carotenogenesis and the final carotenoid content reached depend on the final salinity. The increase in total carotenoid content is mainly due to fl-carotene. Following the salinity up-shock (especially from 10% to 20% NaCl) the proportion of lutein as a percentage of total carotenoids decreases, whereas zeaxanthin increases. This suggests that the pathway synthesising lutein is more sensitive to salt or osmotic stress and is inhibited at higher salinities, thus leading to fl-carotene formation. The proportion of a-carotene does not change.

Production of Polyhydroxyalkanoate (PHA) Biopolyesters by Extremophiles?

“…The manifold strategies of halophile microbes to handle highly saline environments, and the fact that halophilicity occurs throughout the tree of life, suggests that adaptation to high salinity is, from the metabolic point of view, a rather trivial task. Changing pigment patterns in microalgae, which, besides illumination conditions, also is determined by the salinity, is regarded a prime example of the adaptive response to changing environmental conditions [40]. In the case of halophile PHA producers, Soto and colleagues reveled the role of PHA as chaperons, preventing protein agglomeration under combined stress exerted by salt and temperature, by investigating Pseudomonas sp.…”

Carotenogénesis de cinco cepas del alga <i>Dunaliella</i> sp. (Chlorophyceae) aisladas de lagunas hipersalinas de Venezuela

“…Diversos estudios han demostrado que la producción de carotenoides en D. salina puede optimizarse mediante variaciones de las condiciones de cultivo, las cuales incluyen aumento de la salinidad, intensidad luminosa, temperatura (Ben-Amotz 1987, Gómez et al 2003 y/o limitación de nutrientes (Borowitzka y Borowitzka 1988, Borowitzka et al 1990, Mendoza et al 1999.…”

β-Carotene production enhancement by UV-A radiation in Dunaliella bardawil cultivated in laboratory reactors

“…Among the conditions that induce accumulation of carotenoids are high photon flux densities (wavelength range, 400-700 nm). Such inductive conditions have been reported to result in increases of β-carotene levels from 1% dry weight (dw) to 10% dw (2,12,13).…”

“…β-Carotene occurs as a number of isomers, two of which, 9-cis and all-trans, make up approximately 80% of the total β-carotene in the microalgae Dunaliella bardawil (9,11,12). UV radiations have been shown to have both positive and negative effects on the viability of microalgae cultures (14), and some of the commercially attractive carotenoids produced by D. bardawil have absorption in the UV-A spectrum (15).…”