Enhancement of Alcohol Tolerance of Yeast Applying Pressure Stress of Cell and Pressure Reversal of Anesthesia

在乙醇浓度相对较低的情况下，蝌蚪等小型水生动物会沉入水箱底部，但当施加约20兆帕的压力时，它们就会开始游泳。这种在施加压力时从麻醉状态恢复的现象称为麻醉的压力反转，这就是为什么压力经常被用来研究麻醉药的作用机制的原因。在一些微生物中也观察到了这种现象。在对含有几%乙醇的大肠杆菌悬浮液施加压力时，细胞的存活率随着压力的增加而增加，最高可达10-20 Mpa。葡萄糖可产生乙醇，该产品应对细胞起麻醉剂作用。相应地，随着发酵的进行，酵母菌的生长应逐渐减慢，部分细胞会死亡。如果对这个系统施加压力，酵母的存活率应该比常压下的要大。因此，作为这一现象的应用，我们考察了压力逆转对酵母生存的影响，并考察了高压下酵母发酵葡萄糖的情况。酵母菌在无乙醇条件下的存活率随着压力的增加而降低。然而，在含有4%和8%(w/w)乙醇的培养液中，细胞存活率在20 Mpa(200bar)时达到峰值。虽然在20兆帕的压力下，酵母活细胞数明显增加，但在所用的实验条件下没有观察到酒精浓度的增加。

In the presence of relatively low concentrations of ethanol, small aquatic animals such as tadpoles sink to the bottom of a water tank, but they begin to swim when a pressure of about 20 Mpa is applied. This phenomenon of recovery from an anesthetized state on application of pressure is known as pressure reversal of anesthesia and is the reason why pressure is often used to investigate the mechanisms of action of anesthetics. This phenomenon has also been observed with some microorganisms. On application of pressure to suspensions of E.coli containing a few per cent of ethanol, survival of the cells increases with increase in pressure up to 10-20 Mpa.Yeast produces ethanol from glucose and this product should act an anesthetic on the cells. Accordingly, the growth of yeast should gradually be retarded and some cells should die with the progress of fermentation. If pressure is applied to this system, survival of yeast should be greater than at atmospheric pressure. Therefore, as an application of this phenomenon, we examined the pressure reversal for survival of yeast and examined the fermentation of glucose by yeast at high pressure.Pressure revesal of anesthsia was applied to alcoholic fermentation of glucose by yeast. The survival of yeast in the absence of ethanol decreased with increase in pressure. However, in medium containing 4 and 8%(w/w)ethanol, cell survivals reached peaks at 20 MPa(200 bar). Although viable yeast cells apparently increased at a pressure of 20 MPa, no increase of the alcohol concentration was observed under the experimental conditions used.