Study on Newly Isolated Dysmorphococcus Strains from Reunion Island as Potential Sources of High-Value Carotenoids

Certain secondary carotenoids, such as astaxanthin and canthaxanthin, are of growing economic interest in the fields of human nutrition, food, health and cosmetics, as well as feed and aquaculture, particularly due to their numerous biological activities, such as their remarkable antioxidant properties. The present study was devoted to assessing, in a photobioreactor, the feasibility of cultivating newly isolated Dysmorphococcus strains from the biodiversity of Reunion Island for the production of these valuable xanthophylls. The results showed that all these strains were capable of producing and accumulating canthaxanthin and astaxanthin in response to environmental stresses. Among them, a strain which presented interesting morphological, genetic and biochemical properties as compared to the other Dysmorphococcus strains was further cultivated in a 3 L benchtop photobioreactor and was found to produce maximum carotenoid-rich biomass concentrations and productivities of about 4 g L^-1 dw and 0.055 g L^-1 d^-1 dw, respectively. We also found that the biomass contained up to 1.2 mg g^-1 dw of canthaxanthin and 0.7 mg g^-1 dw of different forms of astaxanthin, mainly astaxanthin monoesters. The productivity of these carotenoids was found to be lower than those observed for other microalgal species previously reported, and we suggested that further optimizations with respect to the cultivation and the carotenogenesis induction processes are needed to improve productivities and to make this locally isolated Dysmorphococcus strain useful for future commercial production of natural canthaxanthin and astaxanthin.