Effects of media and photo bioreactor operating parameters in microalgae Dunaliella Salina, increase in beta-carotene content

Abstract

Dunaliella Salina is one of the interesting microalgae producing carotenoids, especially beta-carotene. The amount of beta-carotene produced from Dunaliella Salina is 14% by weight of algae and is much higher compared with carrots and other fruits and vegetables containing this pigment, with considerable disparities. Owing to the importance of the environmental conditions which affect the growth and pigment production of this micro-alga, various studies have been done.

In this study, environmental factors affecting the Dunaliella Salina such as light intensity, temperature, pH, culture medium, NaCl salt content, and bioreactor volume were investigated, and not only the effect of each of these factors but also their interaction effects were studied. Extraction of different materials was carried out with solvent. Optimization of the growth process and obtaining the optimum level of each environmental factor for the growth of various pigments were performed by Minitab software and the Response Surface Method (central composite design). 33 conditions were randomly selected and grown in each of the designated points. The highest biomass production was observed at the light intensity of 12,000 lux, the temperature of 25   C, the pH of 8.75, the NaCl concentration of 0.5 molars, and the volume of 1000 ml of bioreactor. These numbers for the optimized production of beta-carotene were respectively 7636 lux, the approximate temperature of 30   C, the pH equal to 11.7, the NaCl content of 0.5 M and the volume of the bioreactor was approximately 600 ml. The levels of chlorophyll a, chlorophyll b, and total carotenoids were also evaluated. Three replications were done for each experiment to increase the accuracy. Then, using the analysis of variance and considering regression and p-value, experimental relationships were obtained for extracting carotenoids from each microalga. Furthermore, the effects of NaCl shocks, as one of the exacerbated environmental factors, have been studied on growth, beta-carotene, chlorophyll a, and chlorophyll b production.