Schulze U, Lidén G, Villadsen J
Department of Biotechnology, Technical University of Denmark, Lyngby, Denmark.
J Biotechnol. 1996 Apr 18;46(1):33-42. doi: 10.1016/0168-1656(95)00176-x.
Dynamics of the ammonia uptake by Saccharomyces cerevisiae under anaerobic conditions was studied in ammonia limited continuous cultures. A large number of pulse additions of ammonia (25-100 mg 1(-1)) were made at different dilution rates (0.05-0.20 h-1). The response was followed by on-line monitoring of the carbon dioxide evolution rate (CER), optical density, and by frequent analysis of extra- and intracellular metabolites. The uptake of a pulse of ammonia proceeded in a qualitatively highly reproducible pattern. Initially, a rapid and growth rate dependent uptake of ammonia was observed (lasting for about 10-15 min). Next followed a phase with little uptake (approx. 5 min). Finally, the rest of the ammonia pulse was taken up at a somewhat smaller rate which also depended on the growth rate. The first phase coincided with an increase in CER caused by mobilization of the intracellular carbohydrate trehalose and subsequently of glycogen. Regardless of dilution rate and the amount of ammonia added, the initial high uptake rate of ammonia was maintained until approximately the same amount of ammonia had been taken up. Transition from the first to the second uptake phase was associated with an increased glycerol production, indicating an elevated anabolic activity.
在氨限制的连续培养中研究了酿酒酵母在厌氧条件下对氨的吸收动力学。在不同稀释率（0.05 - 0.20 h⁻¹）下进行了大量氨脉冲添加（25 - 100 mg l⁻¹）。通过在线监测二氧化碳释放速率（CER）、光密度以及频繁分析细胞外和细胞内代谢物来跟踪响应。氨脉冲的吸收呈现出高度可重复的定性模式。最初，观察到氨的快速吸收且依赖于生长速率（持续约10 - 15分钟）。接下来是吸收很少的阶段（约5分钟）。最后，氨脉冲的其余部分以稍小的速率被吸收，该速率也依赖于生长速率。第一阶段与细胞内碳水化合物海藻糖随后糖原的动员引起的CER增加相吻合。无论稀释率和添加的氨量如何，氨的初始高吸收速率一直维持到吸收了大致相同量的氨。从第一吸收阶段到第二吸收阶段的转变与甘油产量增加相关，表明合成代谢活性增强。
