Optimization Of Fermentation Parameters For DHA Production With Schizochytrium Sp. B4D1

DHA is one of important long chain polyunsaturated fatty acids. Owing to its special functions in improving the qualities of meat, egg and milk, it has been achieved more and more attentions. DHA contained animal production have been produced in developed countries. However, owing to the limited sources, it can not be widely used like other food additives for animals. The traditional way of producing DHA is exerting from tissues of fish. However, the traditional way brought tremendous pressure to the fishing industry. What’s more, the quality of DHA is not steady owing to the quality and kinds of fish. Our work is to produce a large amount of DHA. The first work is to explore the optimal culture conditions. The second work is to select proper additive according to the metabolic pathway of Schizochytrium sp. B4D1 to improve the yield of DHA. The third work is to make the way of adjusting pH better by using NaOH, ammonia and citric acid to replace the traditional way of using NaOH and sulphuric acid. All these works are aim to improve the yield of DHA.In order to get much more DHA, a new DHA producing strain by the study of the mutation breeding is obtained. So the first work is to explore the optimal culture conditions. The optimal culture conditions is:25℃, pH is 6, the best concentration of yeast in seed medium is 20g/L, the best concentration of glucose is 80g/L, the best concentration of KH2PO4 is 4g/L, in addition, yeast and soybean protein should added initially to supply azote. The proper amino acid and its concentration are listed below (g/L):glycine 2, glusate 1.7, tryptophan 1.6 and lysine 0.3. Under the proper condition, the biomass reached to 33.58g/L, the lipid yield reached to 10.78g/L, the DHA yield reached to 13.80g/L, increased 27%,7%,487% respectively.In order to get much more DHA, citric acid is added to medium according to the metabolic pathway of Schizochytrium sp. B4D1 to improve the yield of DHA. The best concentration of citric acid is 2g/L, added to medium initially. At the end of fermentation, the biomass reached to 146.73g/L, the lipid yield reached to 92.22g/L, the DHA yield reached to 27.63g/L, increased 14%,11%,21% respectively. In order to get much more DHA, the way of adjusting pH is optimized by using NaOH, ammonia and citric acid to replace the traditional way of using NaOH and sulphuric acid. What’s more, as the consumption of oxygen and glucose reduced, ammonia should be replaced by NaOH to avoid the poison of immoderate ammonia. At the end of fermentation, the biomass reached to 97.55 g/L, the lipid yield reached to 77.76g/L, the DHA yield reached to 18.87g/L, increased 49%,70%,18% respectively.