Highly efficient co-production of fucoxanthin and eicosapentaenoic acid by heterotrophic cultivation of a newly isolated microalga Nitzschia sp. FZU62

Abstract

Microalgae can accumulate various compounds simultaneously, thus co-production of high-value metabolites to improve the economic value of microalgae production is feasible. In this study, a microalga strain Nitzschia sp. FZU62 capable of co-producing fucoxanthin and eicosapentaenoic acid (EPA) was isolated and identified. Further, heterotrophic conditions were optimized to improve the co-production efficiency in flasks. Results showed that the optimal conditions for flask culture were cultivation for 84 h with an inoculum size of 0.47 g/L and a temperature of 19 °C. Besides, three fed-batch culture strategies with distinct nutrient compositions were explored to improve the heterotrophic performance of strain FZU62. Results indicated that the highest biomass, fucoxanthin, and EPA productivities were obtained by Fed-batch III, in which concentrated medium was pulse-fed to supply 60 % initial nutrients once glucose concentration dropped to about 2 g/L. Moreover, the heterotrophic performance was verified in a 5 L fermenter, resulting in excellent fucoxanthin and EPA productions of 63.03 and 398.60 mg/L, and productivities of 3.41 and 22.52 mg/L/d, respectively. These results, especially the EPA production and productivity, are superior to many literature reports. The present study provides new insights into the highly efficient co-production of fucoxanthin and EPA by marine microalgae and has guiding significance for commercial production in heterotrophic mode.