Abstract
Background: Benzyl cinnamate is widely used in many fragrance compounds. The traditional methods to obtain benzyl cinnamate, including chemical synthesis or extraction from leaves, have many drawbacks. Recently, lipase-catalyzed synthesis of benzyl cinnamate has provided us with a promising alternative due to its high catalytic efficiency, mild reaction conditions, and green and environmentally friendly process. In this work, the purpose is to investigate the kinetics and thermodynamics of enzymatic synthesis of benzyl cinnamate.
Objective: The objective of the current study was to investigate the kinetics and thermodynamics of the enzymatic synthesis of benzyl cinnamate.
Results: The results showed that the reaction followed the Ping-Pong mechanism leading to substrate inhibition. Furthermore, the kinetic and thermodynamic parameters were estimated. The inhibition constant KiB decreased with temperature enhancement, implying that the inhibition of benzyl alcohol on lipase could be depressed at high temperatures. Moreover, the activation energy of the first-step reaction (52.46 kJ/mol) was much higher than that of the second-step reaction (12.97 kJ/mol), demonstrating that the first-step reaction was the rate-limiting reaction. The esterification process was found to be endothermic, with an enthalpy value (ΔH) of +55.7 kJ/mol and entropy value (ΔS) of +170.2 J/mol K, respectively. Based on the change of Gibbs free energy (ΔG), enzymatic esterification of cinnamic acid changed from non-spontaneous to spontaneous reaction when temperature was raised to above 53ºC.
Conclusion: This obtained information could be utilized to optimize the biosynthesis of benzyl cinnamate.
Keywords: Enzymatic synthesis, benzyl cinnamate, kinetic model, ping-pong Bi-Bi mechanism, substrate inhibition, thermodynamics.
Graphical Abstract
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