Enhanced production of fatty acids and astaxanthin in Aurantiochytrium sp. by the expression of Vitreoscilla hemoglobin.

Dissolved oxygen is a critical factor for heterotrophic cell growth and metabolite production. The aim of this study was to investigate the effects of an oxygen-involved protein on cell growth and fatty acid and astaxanthin production in the biologically important thraustochytrid Aurantiochytrium sp. The hemoglobin of the Vitreoscilla stercoraria (VHb) gene was fused upstream with a zeocin resistance gene (ble) and driven by the Aurantiochytrium tubulin promoter. The expression construct was introduced into two strains of Aurantiochytrium sp. by electroporation. Transgenic Aurantiochytrium sp. strains MP4 and SK4 expressing the heterologous VHb achieved significantly higher maximum biomass than their corresponding controls in microaerobic conditions. Furthermore, the transformants of Aurantiochytrium sp. SK4 produced 44% higher total fatty acid and 9-fold higher astaxanthin contents than the wild type control in aerobic conditions. The present study highlights the biotechnological application of VHb in high-cell density fermentation for enhanced biomass production as well as high-value metabolites.