Abstract

Synthesis of ethyl acetate (EA) using lipase as a catalyst, as an environmentally-friendly process, has attracted considerable attention. However, the slow rate of enzymatic reaction and higher cost limit its applications. Ultrasound irradiation (UI) is known as an effective tool for accelerating the rate of enzymatic reaction under mild conditions. To attain maximum yield, it is crucial to understand the effect of UI on EA synthesis and the underlying mechanism. Therefore, the present study investigated the effect of UI on lipase-catalyzed ethyl acetate synthesis. The results clearly demonstrated that UI could remarkably accelerate the process of lipase-catalyzed synthesis of ethyl acetate compared with mechanical shaking. The optimal conditions of ultrasound-assisted reaction by using Novozyme 435® were 6% enzyme loading, 4:1 molar ratio of ethanol to acetic acid, 150 W & 28 kHz ultrasonic power and frequency, respectively. Bi-bi ping-pong model was employed to give a deep insight into the underlying mechanism of the beneficial effect of UI. It was found that V_max under UI was elevated by 143% compared with that under mechanical shaking. Application of UI could decrease K_{acetic acid} and K_{i ethanol} while increase K_ethanol and K_{i acetic acid} . In conclusion, the present study addresses that UI could remarkably accelerate the process of lipase-catalyzed synthesis of EA compared with mechanical shaking, and kinetic model results explained why ultrasound can significantly speed up lipase catalyzed synthesis of ethyl acetate, which may help to improve the industrial application potential of ethyl acetate biosynthesis.

摘要

使用脂肪酶作为催化剂的乙酸乙酯（EA）的合成，作为一种环境友好的方法，已经引起了广泛的关注。然而，酶促反应速度慢和成本高限制了它的应用。超声辐照（UI）是在温和条件下加速酶促反应速率的有效工具。为了获得最大的收益，至关重要的是要了解UI对EA合成及其基本机制的影响。因此，本研究调查了UI对脂肪酶催化乙酸乙酯合成的影响。结果清楚地表明，与机械振荡相比，UI可以显着加速脂肪酶催化的乙酸乙酯合成过程。使用Novozyme435®进行超声辅助反应的最佳条件是6％的酶负载，4：乙我-双平-乒乓模型采用以得到深入了解的UI的有益效果的基本机制。发现在UI下的V _max 与在机械摇动下相比提高了143％。施用UI可以降低K_乙酸 和K _i乙醇， 同时增加K K_乙醇 和K _i乙酸 。综上所述，本研究解决了UI与机械摇动相比，UI可以显着加速脂肪酶催化的EA合成过程的问题，动力学模型结果解释了为什么超声可以显着加快脂肪酶催化的乙酸乙酯的合成，这可能有助于改善乙酸乙酯的合成。乙酸乙酯生物合成的工业应用潜力。