【作者】 司马迎春；

【导师】 赵学明；

【作者基本信息】 天津大学 ， 生物化工， 2004， 硕士

【摘要】 本文主要研究了酵母粉及其组分在枯草芽孢杆菌24/pMX45核黄素发酵中的作用、氮源与核黄素发酵之间的关系、复合氮源及无机离子对核黄素发酵的影响，探讨了氮源种类和供给的优化。固体种子接种的摇瓶发酵方式，较之液体种子接种的摇瓶发酵方式，其种子质量稳定，对发酵过程的随机干扰作用较小，适用于B.subtilis24/pMX45核黄素发酵工艺的研究。在B.subtilis24/pMX45核黄素发酵过程中，酵母粉提供细胞生长及核黄素合成的氮源，还提供细胞生长所必需的生长因子。酵母粉中某些可溶性组分的过量存在，引起碳分解代谢阻遏作用和溢流代谢，降低核黄素合成速率和产量。酵母粉中含有17种氨基酸，其中谷氨酸的含量占氨基酸总含量的57.87%。发酵液中可溶性谷氨酸浓度超过800mg/l时，能够引起明显的碳分解代谢阻遏作用，降低核黄素合成速率和产量。增加发酵培养基中酵母粉的用量，会导致谷氨酸浓度增加，不利于核黄素合成。2.5%酵母粉用作核黄素发酵的氮源时，氮源的供给不足。NH4Cl、(NH4)2SO4等无机氮源用作2.5%酵母粉的补充氮源，都能够促进发酵液中葡萄糖浓度增高，引起碳分解代谢阻遏效应，不利于核黄素合成。0.2%的尿素作为补充氮源，核黄素积累量可以提高20%。高于0.2%的尿素作为补充氮源，将引起明显的溢流代谢，使核黄素产量的提高幅度降低。基于酵母粉对B.subtilis24/pMX45核黄素发酵的多种作用，尿素用作2.5%酵母粉的补充氮源时，控制发酵液中尿素浓度在发酵过程中长时间在0.2%以下，可以进一步增加核黄素产量的提高幅度。单独加入Zn2+、Mn2+对核黄素合成有利，但同时加入尿素、Zn2+或Mn2+时，由于它们的共同效应，对核黄素合成不利。更多还原

【Abstract】 This work mainly study on the effects of yeast powder and its components on the Bacillus subtilis 24/pMX45 riboflavin fermentation, the relation between nitrogen source and riboflavin fermentation, the influence of composite nitrogen source and inorganic ions on riboflavin fermentation, and discuss the optimize of the kind of nitrogen source and its supply.Inoculation with fresh lawn is more efficient in investigating the rule of riboflavin shake-flask fermentation than with seed solution, it can reduce the steps and avoid the disturbances of seed factor on fermentation.During the fermentation of Bacillus subtilis 24/pMX45, yeast powder provide nitrogen source for cell growth and riboflavin production, supply growth factor to cell. Something of dissolvable substance has no advantage for riboflavin production in yeast powder because it can induce Carbon Catabolite Repression and overflow metabolic. Glu is 57.87% in proportion to all 17 kinds of amino acid in yeast powder. When the concentration of Glu in the culture is beyond 800mg/l, it promotes glucose consuming, induce overflow metabolic and has no advantage to producing riboflavin. So enhancing yeast concentration will enhancing the concentration of Glu, will have harm to riboflavin production.It is not enough that use 2.5% yeast powder as nitrogen source in riboflavin fermentation. Adding inorganic nitrogen source such as NH4Cl、(NH4)2SO4 to culture medium , increase glucose concentration and Carbon Catabolite Repression and have no benefit to riboflavin production. Adding 0.2% urea to 2.5% yeast powder as nitrogen source can promote 20 percent of riboflavin production. To enhance riboflavin production, the urea concentration should below 2000mg/l and maintain long time. Adding Zn2+ or Mn2+ to culture medium is of benefit to riboflavin producing. But adding urea and Zn2+ or Mn2+, the promotion of riboflavin production disappears.更多还原