导　　师： 姚汝华

学科专业： 082203

授予学位： 博士

作　　者： ;

机构地区： 华南理工大学

摘　　要： DHA因其特有的生理调节机能而引起人们极大的兴趣并得到广泛的应用，微生物发酵生产DHA以其独特的优势而成为国内外研究的热点之一。本论文利用一株破囊壶菌/(Thraustochytrium aureum/)ATCC34304为出发菌株，对培养基组分和培养条件优化、高产菌株的选育、DHA发酵的代谢调控及生物反应器放大培养等方面进行了较为深入的研究。 利用五株不同的出发菌株进行DHA发酵试验，试验后通过比较生物量、油脂含量和DHA含量以及工业化发酵生产的可行性等几项指标，发现破囊壶菌/(Thraustochytrium aureum/)ATCC34304的生物量、油脂含量和DHA含量都比较高，而且是海生异养型真菌，发酵周期较短，易于培养和进行代谢调控，故选定破囊壶菌ATCC34304为出发菌株进行发酵研究。 破囊壶菌可以利用多种不同的碳源，玉米淀粉是破囊壶菌发酵生产DHA的最适碳源，玉米淀粉浓度在25～30g／L最为合适。 破囊壶菌在以酵母抽提物为氮源的培养基中生长可获得最大的生物量及最大的DHA产量，故选定酵母抽提物为破囊壶菌ATCC 34304发酵培养基的氮源，且破囊壶菌发酵生产DHA的最适碳氮比在15／1～20／1之间。 破囊壶菌在初始pH值为7.0的培养基中可获得最大生物量，但初始pH值为7.0并不适合破囊壶菌DHA的生成，在初始pH值为6.0的情况下，菌体内脂含量、DHA含量都是最高的，综合考虑，确定破囊壶菌发酵产DHA的最佳初始pH为6.0。 通过正交试验确定最佳玉米淀粉添加浓度为30g／L，酵母抽提物1.72g／L，培养基初始pH值6.5。 通过单因素分析确定最优发酵工艺条件：种子培养时间为48h左右；接种量为10％；发酵温度控制采用变温控制，发酵前期培养温度28℃，培养至第五天时降低培养温度至20℃；摇床转速160r／min；培养� DHA has attracted great interest and got extensive application due to its distinctive physiological function. Owing to its noticeable advantage, DHA production by microorganism has become one of hotspots in research field of the world. From the initial strain, Thraustochytrium aureum ATCC34304, the optimizing of medium components and culture condition, breeding of high DHA yield strain, metabolic regulation and control of DHA fermentation and scale-up culture in bioreactor was mainly studied in this dissertation. DHA fermentation was conducted by five different initial strains. By comparing biomass, fatty content, DHA content and feasibility of industry production, T. aureumATCC34304 was selected to investigate due to its high biomass and DHA content. T. aureum ATCC34304 is a kind of heterotrophic fungi from sea, has short fermentation period, easy to culture and regulate and control its metabolism. T. aureum can use many different carbon sources. Corn starch is optimal carbon source for DHA fermentation by T. aureum. The suitable concentration of corn starch is 25~30g//L. The maximal biomass and DHA production could be got when T. aureum was cultured in medium in which the yeast extract was used as nitrogen source. So the yeast extract was chosen as the nitrogen source for DHA production from T. aureum. The suitable C//N ratio is from 15//1 to 20//1. When the initial pH of medium is 7.0, the maximal biomass was obtained. But it is not suitable for DHA accumulation. The fatty and DHA content is highest in medium with initial pH 6.0. The optimal initial pH, 6.0, was confirmed by comprehensively considering. The optimal addition concentration for corn starch, 30g//L, yeast extract, 1.72g//L, and initial pH, 6.5,were determined by orthogonal experiment. Through single factor analyses, the optimal culture condition was fixed: the culture time for seeds is 48 hour; inoculum volume is 10/%; the changing temperature

关 键 词： 破囊壶菌 发酵 代谢调控

领　　域： [轻工技术与工程]