Research On The Crypthecodium Cohnii For Producing DHA Intensification

Docosahexaenoic Acid( DHA) is one of ω-3-polyunsaturated fatty acids,which is the human essential fatty acids. Due to the unique structure with 6 unsaturated bonds,it has great influences on human healthy.The fish oil of deep sea is the main source of DHA, as various factors limitation, microbial fermentation method has become the main research direction of DHA. In this study,we used Crypthecodinium cohnii mutant strains as the original strain,the optimization of fermentation conditions, the kinetic model of fermentation process and amplification experiment were studied. The main results are as follows:1. Optimization of fermentation medium of Crypthecodinium cohnii for DHA production with response surface methodResponse surface methodology were applied to optimize fermentation medium for DHA production by Crypthecodinium cohnii. First, the glucose,sodium glutamate, Mg SO4 were identified by Plackett-Burman design as main medium components that influence the the yield of DHA, the steepest ascent method and Box-Behnken optimize the culture medium, and establish multivariate regression model. The result showed that the optimal fermentation medium were 121.41 g/L glucose,11.54 g/L sodium glutamate,7.25 g/L Mg SO4,et al. the experimental yield of DHA in the optimized medium was 5.67 g/L,which increased 10.35% than before optimization.2. Optimization of culture conditions of Crypthecodinium cohnii for DHA production with response surface met hodThe single factor tests was used to investigate the effects of inoculums,culture time, culture temperature, volum of liquid, initial p H value of medium on the yield of DHA.On the basis of single factor tests, select the inoculums,initial p H value of medium, volum of liquid as the main influence factors.Through the Box-Behnken design, the optimal culture conditions:9.2% inoculums,initial p H value 6.9,volum of liquid 65 ml/500 ml,the experimentalyield of DHA in the optimized medium was 5.81 g/L,and increased 13.28% than before optimization.3. Through temperature shift increasing the yield of oil and DHA with Crypthecodinium cohniiThrough the analysis of the results of strain in different temperature culture,established a fermentation temperature control s trategy training.through four different fermentation solution result shows, the strain culturing at 27℃for 48 h, then the fermentation temperature reduced to 21 ℃, the oil can reach 14.44g/L, the yield of DHA can reach 5.77 g/L, compared to the single temperature at 27℃, 21℃ were increased 10% and 23%.4. The establishment of the fermentation kinetics for DHA algae oil production by Crypthecodinium cohniiBased on Logistic equation and Luedeking-Piret equation, and the biomass,the yield of oil and DHA were determ ined at designated time, the kinetic models for cell growth, oil production and substrate consumption were established, and the predictive values of models were compared with the experimental data, the average relative errors are less than 10%. Through to the fermentation process of curve fitting and model parameters calculation, the goodness-of-fit scores R2 of models are 0.993、 0.996 and 0.978 which showed they match well.5. Study on feeding glucose fermentation in the fermentor of Crypthecodinium cohnii and completed the pilot productionThe effects of different feed glucose concentration and feed time on DHA yield in Crypthecodinium Cohnii were studied. Through five different glucose concentration and feed time, The biomass, the yield of oil and DHA were determined at designated time.The results showed that the optimum feed glucose time was 54 h,at this time feed 3% glucose, the yield of oil and DHA were 29.76 g/L and 11.94 g/L. Under a 50 T pilot-scale fermentation at the optimal conditions, the average biomass was 2.59 T, the average yield of oil and DHA were 0.98 T and 409.0 kg.