Microbial Process Improvement Through Energy Stress

能量胁迫对酵母代谢有深远的影响，可以促进乙醇的有氧生成，并具有较高的比产率。当细胞受到钾离子水平下降的进一步压力时，葡萄糖浓度升高引起的氧化还原代谢会更快地减少。虽然这为乙醇在好氧条件下而不是厌氧条件下的生产开辟了新途径，但由于乙醇的积累受到抑制，进展缓慢。它还不能证明，既高乙醇产量和高浓度可以实现。本研究采用生物自我调节摄食量的连续培养模式。最先进的计算机控制稳定了培养物。这项工作包括：1。测试不同酵母菌株；2. 研究能量压力对酵母菌（一种商业上用于生产乙醇的细菌）的影响；和3。使用絮凝酵母建立高反应器细胞密度。微生物生产的乙醇已经在与石油生产的乙醇竞争，并有望在汽车燃料中发挥越来越大的作用。更高的生产率和坚固耐用的有氧过程将降低成本。初步的研究表明，每个细胞的生产率很高，但由于乙醇的积累抑制了这一过程，因此无法维持这种生产率。这是一个重要的、真实的效果，挑战在于将其扩展到与商业相关的乙醇浓度范围。这项研究测试了其他酵母菌和一种细菌，单胞菌，以开拓对很少受到关注的生理学领域的新见解。这种新型的计算机连续培养装置以细胞自身新陈代谢所决定的速率喂养细胞。这在显示生长速率对条件变化的反应方面是独一无二的，并导致对关键实验因素的有效筛选。

Energy stress has a profound effect on yeast metabolism and can promote aerobic formation of ethanol with high specific productivity. Oxidoreductive metabolism induced by elevated concentrations of glucose cuts in sooner when the cells are further stressed by depressed levels of potassium ion. Although this opens new approaches for ethanol with aerobic instead of anaerobic conditions, progress is slowed by inhibition as ethanol accumulates. It cannot yet be demonstrated that both high ethanol productivity and high concentration can be achieved. This research uses auxostat mode of continuous culture with self-adjustment by the organisms of their feed rate. State-of-the-art computer control stabilizes the cultures. This work includes, 1. testing of various strains of yeast; 2. investigate effects of energy stress on Zymomonas, a bacterium used commercially to produce ethanol; and 3. operate with flocculating yeast to establish high reactor cell densities. Ethanol produced by microorganisms already competes with ethanol made from petroleum and promises to assume an expanding role in automotive fuels. Greater productivity and a rugged aerobic process would lower costs. Preliminary work demonstrates outstanding productivity per cell but cannot maintain it as ethanol accumulates to inhibit the process. This is an important, real effect, and the challenge is to extend it to commercially relevant ranges of ethanol concentration. This research tests other yeasts and a bacterium, Zymomonas, to exploit new insights into a region of physiology that has had little attention. The novel computerized continuous culture apparatus feeds the cells at a rate determined by their own metabolism. This is unique in displaying growth rate responses to changes in conditions and leads to efficient screening of key experimental factors.