用脱脂蚕蛹水解物作氮源培养裂殖壶菌生产DHA的发酵工艺及动力学研究

Fermentation Process and Kinetic Studies of Using Defatted Silkworm Pupa Hydrolyzate as Nitrogen Source to Culture Schizochytrium limacinum for DHA Production

二十二碳六烯酸（DHA）是人体生长发育所必需的一种多不饱和脂肪酸,裂殖壶菌（Schizochytrium limacinum）因高产富含DHA的油脂而被用于人工发酵生产DHA。为了降低DHA的生产成本,以脱脂蚕蛹水解物作为裂殖壶菌SR21菌株发酵培养基的唯一氮源,并对发酵工艺条件进行优化。以3 L发酵罐培养裂殖壶菌SR21菌株,当脱脂蚕蛹水解物用量为20 g/L、培养温度为26℃、初始p H为6.0、海水晶质量浓度为40 g/L和溶氧量为20%时,菌株发酵培养120 h获得的生物量为39.27g/L,油脂产量22.44 g/L,其中DHA生产效率为62.63 mg/（L·h）。与使用商品化酵母浸粉为培养基氮源相比,以脱脂蚕蛹水解物为氮源培养裂殖壶菌SR21菌株所产油脂的脂肪酸组成保持不变,且DHA产量高达7.52 g/L。利用Logistic模型和LuedekingPiret模型（R^2〉0.99）成功拟合了裂殖壶菌在脱脂蚕蛹水解物作氮源的培养基中生长的动态过程,为后续分批补料培养提供了依据。研究结果表明,脱脂蚕蛹水解物适合作为有机氮源用于培养裂殖壶菌类微藻发酵生产DHA等高附加值油脂。

Docosahexaenoic acid （DHA） is an essential polyunsaturated fatty acid for human growth and development.Because Schizochytrium limacinum is rich in DHA, it has been used in artificial fermentation to produce DHA products. In order to reduce production cost of DHA, de- fatted silkworm pupa hydrolyzate was used as a novel and sole nitrogen source for fermentation of Schizochytri um limacinum SR21, and the fermentation process is opti- mized. When Schizochytrium limacinum SR21 was culti- vated using a 3 L fermentation container, the optimized am- ount of defatted silkworm pupa hydrolyzate was 20 g/L, temperature was 26 ℃, initial pH value was 6.0, con- centration of seawater crystal was 40 g/L, and dissolved oxygen was 20%. After fermenting under the optimal con-ditions for 120 h, the biomass, lipid and DHA productivity were 39.27 g/L, 22.44 g/L and 62.63 mg/（ L-h）, respec- tively. As compared with commercial yeast extract medium, the S. limacinum SR21 cultured using defatted silkworm pupa hydrolyzate as nitrogen source had unchanged fatty acid profiles and higher DHA yield （7.52 g/L）. Logistic model and Luedeking-Piret model were used successfully to simulate the growth process of S. limacinum SR21 in the culture using defatted silkworm pupa as nitrogen source （R2 〉0.99）, providing a good basis for adding material in forthcoming culture. Hence, defatted silkworm pupa hydrolysate can serve as an ideal organic nitrogen source to culture microalgae such as S. limacinum SR21 for production of DHA and other high value added lipids.