Enhanced production of carotenoids using a Thraustochytrid microalgal strain containing high levels of docosahexaenoic acid-rich oil

Results to date suggest that microalgal Thraustochytrids family strains can be used to produce high-functional omega-3 rich oil (~ 30–70% of dry cell weight) and carotenoid-based antioxidant pigments simultaneously with value-added bioactive potential. In the present study, we describe the isolation and characterization of a new Thraustochytrid Schizochytrium sp. from the west coastal area of Korea. This newly isolated Thraustochytrid, identified as Schizochytrium sp. through 18S rRNA analysis and named SH104, simultaneously produces high levels of DHA and carotenoid-based antioxidant pigments. An improved Schizochytrium mutant, named SHG104, was obtained from the original host strain by γ-irradiation-induced mutagenesis. Under combined temperature-shift cultivation conditions employing white-light LEDs (light-emitting diodes), Schizochytrium sp. SHG104 yielded 10.8 g L⁻¹ of biomass comprising 45.8% total lipids (32.1% DHA) and 4.6 mg L⁻¹ of astaxanthin. In addition to DHA, the main fatty acids produced by Schizochytrium sp. SHG104 were palmitic acid and a trace of other long-chain fatty acids. The carotenoid profile of SH104 and SHG104 was β-carotene, astaxanthin, canthaxanthin, pheonicoxanthin and echinenone, which analyzed by HPLC and LC/APCI–MS. Furthermore, genomic analysis of Schizochytrium and Aurantiochytrium microalgae confirmed that the presence of carotenogenesis pathway enzymes and genes including geranylgeranyl diphosphate, phytoene synthase, lycopene cyclase, and cytochrome P450 hydroxylase that necessary for the production of antioxidants via a complete biosynthetic KEGG synthesis pathway. This newly isolated Schizochytrium microalga potentially have wide application as a source of antioxidants for astaxanthin-containing pigments, commercial omega-3 lipids and feed additives, such as nutritional supplements for aquaculture.