高分子量聚谷氨酸的微生物合成及其发酵过程的研究

目的：以枯草芽孢杆菌纳豆亚种为出发菌株，考察不同碳氮源及NaCl浓度、谷氨酸、种龄、接种量对微生物发酵产1-聚谷氨酸的影响，以提高γ-聚谷氨酸的产量。方法：该菌菌种活化后，接入种子培养基，于37℃、200r／min震荡培养18h，然后按2％接种量接入不同发酵培养基进行发酵培养。γ-聚谷氨酸分离纯化后，根据其产量筛选最适发酵培养基组成及发酵条件，并对产物进行分析测定。结果：①最佳碳氮源分别为葡萄糖、蛋白胨，NaCl浓度为30g／L、种龄15h、接种量3％，且需在培养基中添加谷氨酸。②该菌株在最适条件下发酵56h时，γ-聚谷氨酸产量达32．7g／L，凝胶渗透色谱分析其相对分子质量为426kDa，呈多分子质量聚集体形式。③γ-聚谷氨酸的合成与菌体生长并非完全同步。结论：γ-聚谷氨酸作为一种天然的、可生物降解的、对环境和人体无害的多聚物，可由微生物发酵合成，且在此适宜条件下产量较高。

Study on Biosynthesis and Fermentation of Polyglutamic Acid with High Molecular Weight

Objective： To investigate the effects of the fermentation conditions, such as carbon source, nitrogen source, concentration of NaCl, glutamic acid, species age, inoculation size on the γ-polyglutamic acid production using Bacillus subtitis natto and to enhance the γ-polyglutamic acid production. Methods： The strain was inoculated into the seed medium after activated and was cultured 18 h shakingly. Then it was inoculated into different fermentation mediums with 2 % inoculation size. We screened the optimum fermentation medium composition and the cOnditions by the yield of γ-polyglutamic acid after it was isolated and purified. Furthermore we analysed and determined the product. Results：①The optimal carbon source and nitrogen source was glucose and peptone respectively, and NaCI 30 g/L, species age 15h, inoculation size 3 %, a certain amount of glutamic acid. ②When the strain was fermented for 56 h in the optimum conditions, the yield of γ-polyglutamic acid reached 32.7 g/L. The relative molecular weight was 426 kDa by gel permeation chromatography, displaying polydisperse formation. ③The fermentation process of γ-polyglutamic acid synthesis and cell growth was not completely synchronized. Conclusion： γ-potyglutamic acid, a natural, biodegradable, innocuous to human and environment polymer, could be produced by microbial fermentation and the yield was higher under appropriate conditions.