Document Type: Research Paper
Department of Biotechnology, Institute of Science and High Technology and Environmental Sciences, Graduate University of Advanced Technology, Kerman, Iran
Institute of Science and High Technology and Environmental Sciences, Graduate University of Advanced Technology, Kerman, Iran
department of chemical engineering, facultu of Faculty of Engineering, yazd
Background: Docosahexaenoic acid "a polyunsaturated fatty acid" plays an important role in the prevention of arteriosclerosis and cardiovascular diseases. Thraustochytrid protists, specifically Aurantiochytrium strains. are one of the main microbial producers of this omega-3 fatty acid.
Objectives: Enhancement of biomass, oil and DHA content of Aurantiochytrium sp. by glucose or glycerol feeding of culture in a 3L-fermentation system is the main object of this research.
Materials and Methods: A native strain of Aurantiochytrium sp. qe-4 (KR091914.1) was used for docosahexaenoic acid (DHA) production. Glycerol and glucose were applied as a carbon source in a defined medium. Cell growth, lipid and docosahexaenoic acid (DHA) accumulation in Aurantiochytrium sp. were studied under fed-batch cultivation by using the accurate feeding techniques in a 3 L fermenter.
Results: The results indicated that at C:N ratio of 1.5 and medium composition of 30 g.L-1 glycerol, 10 g.L-1 peptone, and 10 g.L-1 yeast extract, the native strain of Aurantiochytrium was achieved biomass, lipid content, and DHA concentration of 30.2 g.L-1, 8.8 g.L-1, and 1.7 g.L-1, respectively. Also at C:N ratio of 2 and medium composition of 40 g.L-1 glucose, 20 g.L-1 sodium glutamate and 6 g.L-1 yeast extract, 27.6 g.L-1 biomass, 12.5 g.L-1 lipid content, and 1.45 g.L-1 DHA concentration were achieved respectively. Moreover, MSG-feeding combined with glucose feeding strategy was extremely useful for DHA production. It had been proved that low dissolved oxygen (less than about 3% of saturation) was efficient for DHA production.
Conclusions: During the fermentation process, dissolved oxygen values and carbon-to-nitrogen ratios are critical factors that influencing microorganism growth and DHA synthesis. These results showed that the native strain of Aurantiochytrium with glycerol source had better performance than the glucose source for production of DHA. Also, the results proved that native strain of Aurantiochytrium was capable for DHA production in industrial scale.