Abstract To enhance the reaction rate and yield during biodiesel synthesis with Novozym 435 (an immobilized lipase), a co-solvent method was applied, after which the relationships between reaction time and reaction yield during the single-phase enzymatic transesterification of triolein and methanol in the presence of co-solvents such as tetrahydrofuran, acetone, and hexane were investigated. The addition of hexane led to inactivation of Novozym 435, whereas in the presence of acetone or tetrahydrofuran, the reaction was accelerated and the yield was higher than with a conventional solvent-free enzymatic reaction. There was a clear difference in the dispersion of Novozym 435 particles between with and without co-solvents. The co-solvents prevented particle aggregation from occurring during the reaction without co-solvent. This is the likely reason for the enhanced reaction yield in the presence of co-solvents. To better understand the difference among the co-solvents employed, we estimated phase compositions during transesterification using the LLE (liquid-liquid equilibrium)-UNIFAC (UNIversal quasichemical Functional group Activity Coefficients) model, and examined the effect of these compositions on the reaction and dispersion of the glycerin by-product phase. Using the model, we also accounted for why hexane led to inactivation by estimating the transfer free energy of methanol, glycerin, and water between the initial bulk reaction solution and the water layer on the enzyme surface.

中文翻译：

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使用共溶剂使用 Novozym 435 对三油精和甲醇进行酯交换

摘要 为了提高 Novozym 435（一种固定化脂肪酶）合成生物柴油的反应速率和产率，采用共溶剂法，研究了三油酸甘油酯和甲醇单相酶促酯交换过程中反应时间与反应产率之间的关系。研究了共溶剂如四氢呋喃、丙酮和己烷的存在。己烷的加入导致 Novozym 435 失活，而在丙酮或四氢呋喃的存在下，反应加速，产率高于传统的无溶剂酶促反应。Novozym 435 颗粒在有助溶剂和无助溶剂的情况下的分散存在明显差异。共溶剂防止在没有共溶剂的反应过程中发生颗粒聚集。这是在共溶剂存在下提高反应产率的可能原因。为了更好地理解所用助溶剂之间的差异，我们使用 LLE（液-液平衡）-UNIFAC（通用准化学官能团活性系数）模型估计了酯交换过程中的相组成，并检查了这些组成对反应和甘油副产物相的分散。使用该模型，我们还通过估计甲醇、甘油和水在初始本体反应溶液与酶表面水层之间的转移自由能，解释了己烷导致失活的原因。我们使用 LLE（液-液平衡）-UNIFAC（通用准化学官能团活性系数）模型估计了酯交换过程中的相组成，并检查了这些组成对甘油副产物相的反应和分散的影响。使用该模型，我们还通过估计甲醇、甘油和水在初始本体反应溶液与酶表面水层之间的转移自由能，解释了己烷导致失活的原因。我们使用 LLE（液-液平衡）-UNIFAC（通用准化学官能团活性系数）模型估计了酯交换过程中的相组成，并检查了这些组成对甘油副产物相的反应和分散的影响。使用该模型，我们还通过估计甲醇、甘油和水在初始本体反应溶液与酶表面水层之间的转移自由能，解释了己烷导致失活的原因。