Effects of Culture Medium Enrichment with Zinc on Astaxanthin Accumulation in a New Strain of the Microalga Dysmorphococcus globosus

High Zn²⁺ concentrations in microalgal cells that produce astaxanthin as a feed additive can reduce the symptoms of malnutrition in aquatic animals. Therefore, in this study, we analysed the effect of Zn²⁺ in the culture medium on the growth of a newly isolated microalgal strain Dysmorphococcus globosus ZY24. Zn²⁺ and white light stress altered the pigment content in microalgal cells. In addition, high Zn²⁺ concentrations in the culture medium altered cell morphology and chlorophyll fluorescence and also increased intracellular Zn²⁺ accumulation. Further, an optimal Zn²⁺ concentration in the culture medium promoted the synthesis of astaxanthin and other pigments. When the concentration of Zn²⁺ was 45.5 mg L^-1, Dysmorphococcus globosus ZY24 produced 0.31 mg g^-1 astaxanthin, whereas the total zinc content of the microalgae was 4337 mg kg^-1. This study confirmed that microalgae have a high capacity for Zn²⁺ enrichment, providing a theoretical basis for studying Zn²⁺ enrichment in microalgae. Furthermore, Zn²⁺ supplementation to stimulate astaxanthin production in microalgae is a practical method to enhance their nutritional value.