无溶剂酶促合成癸酸偏甘油酯的热力学和动力学

Studies on Thermodynamics and Kinetics in Enzymatic Synthesis of Partial Glycerides in Solvent-free Media

以Candidaantarctic脂肪酶(CAL)为催化剂,对无溶剂微水体系中癸酸与甘油酯化反应的热力学平衡和动力学行为进行研究.用平板冷却猝灭法观察反应体系的初始相态.反应物猝灭态照片表明,相间传质与反应物分散状态有关;酶粒表面局部癸酸浓度相对过剩于界面相浓度.在无溶剂体系中癸酸和甘油的酶促反应不符合Ping-PongBi-Bi机制.敞开物体系中单、二、三酯形成的表观热力学平衡方程为:[C]0N[C]/[M]=1/K1+[C]+K2[C]2+K2K3[C]3,其中[C]0为癸酸的初始摩尔数,[C]为反应物中癸酸的摩尔数,N为甘油与癸酸的初始摩尔比,[M]为反应物中癸酸单甘酯的摩尔数;K1、K2、K3分别为单、二、三酯形成的表观热力学平衡常数:K1=0.103mmol-1,K2=0.055mmol-1,K3=0.004mmol-1.

Kinetic behavior and apparent thermodynamics equation of esterification of glycerol with capric acid by using lipase from candida antarctic (CAL) were studied. Initial phase\|state of reaction system was observed with a flat plate cooling\|quenching method. Photos taken from cooling\|quenching reactant show that the mass transfer between phases is related to the dispersing state of reactants; the microenvironmental concentration of capric acid surrounding the surface of immobilized lipase is higher than that in bulk phase. The kinetic behavior is not in accordance with Ping\|Pong Bi\|Bi mechanism. For open system, the apparent thermodynamic equilibrium equation is: 0N/= 1/K1++ K22 +K2K33, where 0 is the initial molar weight of capric acid, N is the initial mol ratio of glycerol to capric acid, and are the molar weight of capric acid and monoglyceride in reaction mixture respectively, and K1, K2, K3 are the apparent thermodynamic equilibrium constants of the formation of monoglyceride, diglyceride and caprin, respectively: K1=\{0.103\} mmol-1, K2=0.055 mmol-1, K3=0.004 mmol-1.