Effect of Solvent on Acyl Migration of 2-Monoacylglycerols in Enzymatic Ethanolysis

Abstract

Acyl migration occurs in many reactions and is the main obstacle for structured lipid synthesis. In this study, 2-monoacylglycerol (2-MAG) was prepared by enzymatic ethanolysis in three different media to evaluate the effect of environment on product composition. The contents of 2-MAG obtained in ethanol, hexane + ethanol, and t-butanol + ethanol systems were 30.6, 15.7, and 32.4%, respectively, after 3 h reaction. Afterward, the acyl migration kinetics of 2-MAG were studied in solvent and solventless systems without the use of lipase. Results indicate that 2-MAG in the solventless system had the highest acyl migration rate. The isomerization was efficiently prevented by the use of polar solvents, especially t-butanol. The rate constants were shown to be the highest and activation energy values were the lowest in solventless systems. The novel finding in this study was that solvent had inhibitory effect on 2-MAG isomerization, but the nonpolar hexane had the lowest inhibition of acyl migration compared to other solvents.

Preparation of 2-Arachidonoylglycerol by Enzymatic Alcoholysis: Effects of Solvent and Water Activity on Acyl Migration

“…Figure 1 b shows that the highest 2-MAG content (24.87%) obtained in the crude product after 8 h was observed in the Lipozyme TL IM-catalyzed system, considerably higher than the contents in Lipozyme 435- and Lipase CL IM-mediated systems. The 2-MAG content in alcoholysis product obtained with Lipozyme 435 or Lipase CL IM as biocatalysts reached the maximum at 4 h before decreasing, possibly due to a high load of immobilized material and a long reaction time, increasing the probability of 2-MAG isomerization to 1-MAG, which was further converted to FAEE and glycerol by a 1,3-specific lipase, ultimately leading to a decrease in 2-MAG yield [ 20 ]. Compared to Lipozyme 435 and Lipase CL IM (approximately 2300 USD/kg), Lipozyme TL IM is inexpensive (approximately 100 USD/kg).…”

“…Compared to Lipozyme 435 and Lipase CL IM (approximately 2300 USD/kg), Lipozyme TL IM is inexpensive (approximately 100 USD/kg). In previous 2-MAG synthesis reactions, most studies used catalytic efficiency as a measure and lipase B from Candida antarctica as the optimum lipase to catalyze the alcoholysis reaction [ 17 , 19 , 20 , 29 ]. However, in this study, the same catalytic efficiency was obtained with 8% Lipozyme 435 and 15% Lipozyme TL IM.…”

“…Compared to chemical synthesis, enzymatic synthesis has the advantages of milder reaction conditions, easily available raw materials, higher selectivity, limited byproducts, and less waste production, and is more suitable for production of 2-AG [ 18 ]. Enzymatic alcoholysis is an efficient way to obtain 2-AG using lipase B from Candida antarctica [ 17 , 19 , 20 ]. Regardless of the methods used, acyl migration, a spontaneous thermodynamic process, is inevitable in 2-MAG synthesis [ 20 , 21 , 22 ].…”

“…Enzymatic alcoholysis is an efficient way to obtain 2-AG using lipase B from Candida antarctica [ 17 , 19 , 20 ]. Regardless of the methods used, acyl migration, a spontaneous thermodynamic process, is inevitable in 2-MAG synthesis [ 20 , 21 , 22 ]. Generally, the fatty acid originally at the sn-2 position is spontaneously transferred to the sn-1 position to form undesirable 1-monoacylglycerol (1-MAG), resulting in decreased yield of 2-MAG and activity loss.…”

“…Previous studies have shown that acyl migration reaches equilibrium at a 9:1 ratio of 1-MAG to 2-MAG [ 22 ]. Thus, to prepare 2-MAG with a high yield, it is necessary to understand the process and inhibition of acyl migration in enzymatic alcoholysis [ 20 , 23 ]. Many factors affect acyl migration of 2-MAG, including a w , temperature, time, type of solvent, and carrier material of the immobilized enzyme [ 24 , 25 , 26 ].…”