Ultrasound irradiation accelerates the lipase-catalyzed synthesis of methyl caffeate in an ionic liquid

• Ultrasound irradiation accelerates the enzymatic synthesis of MC in an ionic liquid.
• A maximum yield of 99.79% was obtained in [Bmim][Tf2N] under ultrasound irradiation.
• Reaction time decreased 0.75-fold, and kinetic parameter (Vm/Km) increased 2-fold.
• Lipase Novozym 435 could be reused 11 times while maintaining MC yields above 82%.

Methyl caffeate is a natural ingredient with several biological activities, but its preparation is generally limited to chemical synthesis. To set up a simple, high-yield and low-cost synthesis process for obtaining methyl caffeate, a novel synthesis method using the lipase-catalyzed esterification of methanol and caffeic acid in an ionic liquid under ultrasound irradiation was established. A maximum yield of 99.79% was obtained using ultrasound irradiation with an ultrasound frequency of 25 kHz and ultrasound power of 150 W under the following optimal conditions: Novozym 435 as a biocatalyst, [Bmim][Tf2N] as the reaction medium, lipase concentration of 60 g/L, reaction temperature of 75 °C, and reaction time of 9 h. Using the optimal conditions under ultrasound irradiation, the reaction time was reduced 0.75-fold, and the apparent kinetic parameter (Vm/Km) was increased 2-fold. The lipase could be reused 11 times without significant loss of activity. The results suggest that ultrasound irradiation can accelerate lipase-catalyzed synthesis of methyl caffeate in an ionic liquid.

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