Production of Protein and Fatty Acids by Aurantiochytrium limacinum in Batch Fermentation

Thraustochytrids can be a promising raw source of nutritionally valuable compounds, particularly protein and fatty acids. The high cost of carbon and nitrogen sources remains a major bottleneck for the industrial-scale heterotrophic cultivation of thraustochytrids. The current study investigates the potential of Aurantiochytrium limacinum SR21 (ATCC MYA-1381) as a rich source of protein and fatty acids, using sea salt, glucose, and different protein extracts as nitrogen sources (peptone vs. yeast extract). Five fermentation media with varying combinations of sea salt, synthetic sea salt, yeast extract, and peptone were evaluated in shake flasks to identify the best-performing medium nutrient composition. The best-performing condition was then scaled-up to a stirred bioreactor with controlled pH. Dry biomass concentration, viable cell count, fatty acid profile, and protein content were evaluated. The bioreactor yielded a maximum of 1.98 ± 0.040 g/L dry biomass containing 19% protein and 1528 ± 110 mg/100 g biomass of docosahexaenoic acid (DHA) in the bioreactor, while the highest DHA concentration (3994 ± 131 mg/100 g dry biomass) was achieved in flask fermentation. Optimizing cultivation conditions and maximizing production yield can transform thraustochytrids, such as A. limacinum, into promising sources of protein and fatty acids for the food industry.