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Docosahexaenoic acid (DHA) is a very important omega-3 series highly unsaturated fatty acids has important physiological functions of promoting infant brain development, eyesight protection, the prevention of cardiovascular disease and improve the immune capacity. Therefore, DHA has been widely used in the production of infant food, health food and adjuvant therapy, etc., preparation and processing methods have attracted attention. Commercial fish oil restrictions due to the supply of fish resources, DHA content is low, the smell of fish and many other negative factors, it is difficult to meet the market demand. Therefore, the development of safe, reliable new source of DHA has become a research focus. A marine fungus, high bacteria DHA content, grow fast, easy to train, non-toxic to humans and animals, is a highly industrialized production prospects DHA microbial resources schizont chytrid fungus Schizochytrium sp. In this thesis, the process and the process of how to achieve the high density of the schizont chytrid fungus culture. DHA extraction method, dried at 125 ℃ for 3 h high-temperature drying method is the better lysing the law both to ensure full lysing, but also conducive to the extraction of DHA. Through the comparison of various lipid extraction method to come up with a new one acidic n-hexane/ethyl method of lipid extraction method, i.e. the microbial cells after high-temperature drying, by hydrolysis with hydrochloric acid first, then n-hexane extraction, the method to achieve a lipid the full quality, efficient extraction. Followed by 5 L German B. Braun fermenter schizont chytrid fungus cultured optimize the fermentation conditions such as pH, dissolved oxygen, determine the optimum batch culture fermentation conditions: temperature 25 ° C, pH 5.5, 30% of the dissolved oxygen level ventilation 4 L / min. Under this condition, the final biomass, fatty acids and DHA content of 36.7 g / L, 23.8g / L and 5.4 g / L, respectively, than before optimization increased 10.0%, 16.7% and 38.6%, the DHA an average yield of r DHA 56.8 mg / (hL). Then, according to the the schizont chytrid fungus batch fermentation characteristics, through constant speed flow plus concentrated medium and glucose (600 g / L) and variable-speed flow plus glucose (600 g / L) two fed-way visits, too shift between 10-20 g / L of glucose concentration in the stream addition method the sustain schizont dendrobatidis more favorable growth and accumulation of fatty acids, and cultured for 5 days, the biomass, fatty acids and DHA content was 60.6 g / L, 40.2 g / L and 8.0 g / L, r DHA 66.7 mg / (hL). On this basis, by the 30 L fermenter enlarged culture, the biomass reached 55.5 g / L, and the fermentation broth after membrane filtration, spray drying the DHA powder is, a DHA content of 13.5 g/100 g The powder. Finally, a semi-synthetic medium reported based on fed-batch culture schizont chytrid fungus, investigated the impact of vitamin and trace elements added schizont chytrid fungus growth and DHA production, further optimization of the fermentation medium. Optimized medium further determine fed-batch culture program, namely through the nutrient solution flow pre-logarithmic phase (24 h) plus N ratio of 36:1, the flow increases in the late logarithmic phase (84 h) high concentrations of glucose (600 g / L) after 120 h of fermentation, the biomass reached 73.0 g / L, DHA yield of 9.8 g / L increased 1.2 times and 1.5 times, respectively, than before optimization of batch fermentation, and r < sub> DHA 81.9 mg / (Lh).
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