Department of Microbiology, Faculty of Medicine, National University of Singapore, Lower Kent Ridge Road, Singapore 0511.
Biotechnol Bioeng. 1989 Jan 10;33(2):183-90. doi: 10.1002/bit.260330207.
Shearing experiments were conducted in a stirred tank reactor with 0.1% lipase solutions of Candida cylindracea. Inactivation of the lipase solutions were observed at various shear rates from 50 to 150 s(-1) after continuous shearing for ca. 30-240 min under optimal pH and temperature conditions. However, there was no shear stress denaturation of the lipase when it was subjected to shear stresses of 0.72-109.2 kg/m/s(2) and shear rate of 100 s(-1). In the presence of polypropylene glycol, the rate of denaturation of the lipase decreased by 93%. When the lipase solution was filled to the brim, the rate of denaturation of the lipase decreased by 97% compared to that when reactor was half-filled. The rate of denaturation of the lipase decreased by 61% when probes in the fermentor were removed. There was no significant difference in the rate of denaturation of the lipase under ambient conditions compared with that in the absence of oxygen, or in the absence of free metal ions. Recovery of lipase activity from the first hour of shearing was observed at a shear rate of 150 s(-1). The native lipase and the lipase which had recovered its activity showed similar pH profiles, temperature profiles, and activation energies. Temperature was found to have no effect in the rate of shear-induced denaturation of the lipase in the range 20 to 30 degrees C during shearing at 100 s (-1)and optimal pH. Above 30 degrees C, the rate of denaturation of the lipase increased drastically as a function of temperature. The significance of the findings in the de sign of reactor systems for hydrolysis or esterification of oils by lipase will be discussed.
在带有 0.1%脂肪酶（来自 Candida cylindracea）的搅拌罐式反应器中进行了剪切实验。在最佳 pH 和温度条件下，连续剪切约 30-240 分钟后，观察到各种剪切速率（50-150 s(-1)）下脂肪酶溶液失活。然而，当脂肪酶受到 0.72-109.2 kg/m/s(2) 的剪切应力和 100 s(-1)的剪切速率时，没有发生剪切应力变性。在聚丙二醇存在的情况下，脂肪酶的变性速率降低了 93%。当将脂肪酶溶液装满时，与反应器半满时相比，脂肪酶的变性速率降低了 97%。当发酵罐中的探头被移除时，脂肪酶的变性速率降低了 61%。在环境条件下，与不存在氧气或不存在游离金属离子相比，脂肪酶的变性速率没有显著差异。在 150 s(-1)的剪切速率下，观察到从剪切的第一个小时开始恢复脂肪酶活性。天然脂肪酶和恢复其活性的脂肪酶表现出相似的 pH 曲线、温度曲线和活化能。发现温度在 20 至 30°C 的范围内，在 100 s(-1)和最佳 pH 下剪切时，对脂肪酶的剪切诱导失活速率没有影响。高于 30°C 时，脂肪酶的失活速率随着温度的升高而急剧增加。这些发现对于设计用于脂肪酶水解或酯化油脂的反应器系统具有重要意义，将在本文中进行讨论。
