Dihydrogen-bonding deep eutectic solvents as reaction media for lipase-catalyzed transesterification

Choline chloride (ChCl)-based deep eutectic solvents (DESs) were successfully used as reaction media for the Candida antarctica lipase B-catalyzed transesterification. The activity of lipase in the DESs was highly influenced by the water activity of the DESs, with optimal lipase activity at a water activity of 0.1. Seventeen DESs containing one or two hydrogen bond donors (HBDs) were used for lipase-catalyzed transesterification at a selected water activity. The highest lipase activity was obtained in ChCl:urea:formamide (molar ratio of 1:1:1), whereas the highest lipase stability was achieved in ChCl:glycerol:ethylene glycol (1:1:1). In general, higher lipase activity was achieved in DESs containing amide HBDs, whereas higher lipase stability was obtained in DESs containing hydroxyl HBDs. The effects of the DESs on the activity and stability of the lipase were evaluated by determining the solvatochromic parameters. Correlation of the solvent parameters of the DESs with the lipase stability showed that the lipase stability increased with an increase in polarity based on Reichardt's dye and the hydrogen bond acidity of the DESs.