Abstract
Bicarbonate has been considered as a better approach for supplying CO(2) to microalgae cells microenvironments than gas bubbling owing t°Cost-effectiveness and easy operation. However, the β-carotene production was too low in Dunaliella salina cultivated with bicarbonate in previous studies. Also, the difference in photosynthetic efficiency between these tw°Carbon sources (bicarbonate and CO(2)) has seldom been discussed. In this study, the culture conditions, including NaHCO(3), Ca(2+), Mg(2+) and microelement concentrations, were optimized when bicarbonate was used as carbon source. Under optimized condition, a maximum biomass concentration of 0.71 g/l and corresponding β-carotene content of 4.76% were obtained, with β-carotene yield of 32.0 mg/l, much higher than previous studies with NaHCO(3). Finally, these optimized conditions with bicarbonate were compared with CO(2) bubbling by online monitoring. There was a notable difference in F(v)/F(m) value between cultivations with bicarbonate and CO(2), but there was no difference in the F(v)/F(m) periodic changing patterns. This indicates that the high concentration of NaHCO(3) used in this study served as a stress factor for β-carotene accumulation, although high productivity of biomass was still obtained.