Condition optimization and kinetic evaluation of Novozym 435-catalyzed synthesis of aroma pyridine esters

A new method for rapid synthesis of pyridine esters without stirring based on Novozym 435 catalysis had been reported, which was from pyridine methanols and vinyl esters. Based on single factor experiment, the optimization of the enzymatic transesterification was received by response surface methodology (RSM). The high yield of 82% was still reached when Novozym 435 had been recycled 12 times. Under optimal conditions, a total of 22 pyridine esters were synthesized. The kinetic model of Novozym 435-catalyzed transesterification of vinyl acetate with 3-pyridinemethanol was established by enzymatic assay. It was discovered that the reaction followed the Ping-Pong Bi-Bi mechanism, and 3-pyridinemethanol inhibited the reaction. Gas chromatography-mass spectrometry-olfactometry (GC–MS-O) was used to analyze the synthesized pyridine esters, of which pyridin-3-ylmethylhexanoate ( 3e ), pyridin-3-ylmethylcinnamate ( 3i ), and 2-(pyridin-2-yl)ethyl acetate (3 s) possessed strong and excellent aromas. These three flavor compounds ( 3e, 3i and 3 s) were found to have good stability at the specified temperature by thermogravimetric (TG) analysis.