Characterization and Optimization of Culture Conditions for Aurantiochytrium sp. SC145 Isolated from Sand Cay (Son Ca) Island, Vietnam, and Antioxidative and Neuroprotective Activities of Its Polyunsaturated Fatty Acid Mixture

Aurantiochytrium is a heterotrophic marine microalga that has potential industrial applications. The main objectives of this study were to isolate an Aurantiochytrium strain from Sand Cay (Son Ca) Island, Vietnam, optimize its culture conditions, determine its nutritional composition, extract polyunsaturated fatty acids (PUFAs) in the free (FFA) and the alkyl ester (FAAE) forms, and evaluate the antioxidation and neuroprotection properties of the PUFAs. Aurantiochytrium sp. SC145 can be grown stably under laboratory conditions. Its culture conditions were optimized for a dry cell weight (DCW) of 31.18 g/L, with total lipids comprising 25.29%, proteins 7.93%, carbohydrates 15.21%, and carotenoid at 143.67 µg/L of DCW. The FAAEs and FFAs extracted from Aurantiochytrium sp. SC145 were rich in omega 3–6–9 fatty acids (40.73% and 44.00% of total fatty acids, respectively). No acute or subchronic oral toxicity was determined in mice fed with the PUFAs in FFA or FAAE forms at different doses over 90 days. Furthermore, the PUFAs in the FFA or FAAE forms and their main constituents of EPA, DHA, and ALA showed antioxidant and AChE inhibitory properties and neuroprotective activities against damage caused by H2O2- and amyloid-ß protein fragment 25–35 (Aβ25-35)-induced C6 cells. These data suggest that PUFAs extracted from Aurantiochytrium sp. SC145 may be a potential therapeutic target for the treatment of neurodegenerative disorders.