Effect of water activity on the lipase catalyzed esterification of geraniol in ionic liquid [bmim]PF₆

Abstract

Enzymatic reactions in non-aqueous media have been shown to be effective in carrying out chemical transformation where the reactants are insoluble in water or water is a byproduct limiting conversion. Ionic liquids, liquid organic salts with infinitesimal vapor pressure, are potentially useful alternatives to organic solvents. It is known that the thermodynamic water activity is an important variable affecting the activity of enzymes in non-aqueous solvents. This study investigated the influence of water activity on the esterification of geraniol with acetic acid in ionic liquid [bmim]PF6 catalyzed by immobilized Candida antarctica lipase B. The conversion of geraniol in [bmim]PF6 was significant although the reaction rate was slower than in organic solvents. The profile of initial reaction rate-water activity was determined experimentally, and differed from the data reported for other non-aqueous solvents. A maximum in the initial reaction rate was found at aw = 0.6. The pseudo reaction equilibrium constant, Kx, was measured experimentally for the reaction. The average value of Kx in [bmim]PF6 was 12, 20-fold lower than the value reported for the same system in hexane.

Immobilization of Candida antarctica Lipase B on fumed silica

“…This approach has for example proven to be promising for the production of polymers 3,4 , anticancer and antiviral drugs 5 , aromas and fragrances 6,7 , and surfactants 8 . Performing biocatalysis in organic solvents is advantageous mainly because the solubility and stability of substrates and products are increased, thereby facilitating their transformation 1,9 , and because undesirable reactions, including hydrolysis, racemization, polymerization, and decomposition may be reduced when compared to aqueous systems 1,10 .…”

Production of Oleic Acid Ethyl Ester Catalyzed by Crude Rice Bran (Oryza sativa) Lipase in a Modified Fed-batch System: A Problem and its Solution

“…Free Fatty Acid (FFA), OAEE, ethanol, water and the conversion of ester were calculated according to Lee et al [14]; Prastowo et al [5]; Segupta and Modak [15]; Barahona et al [16], and Mat Radzi et al [17], respectively.…”

Using ionic liquids in whole-cell biocatalysis for the nucleoside acylation

“…Both the membranes mainly consist of a lipid bilayer in which a large number of enzymes and transport proteins may be embedded [6,29,30]. The hydrophobic ions (such as [PF 6 ]) endow the ILs with lipophilicity (like ionic surface active agents), thus facilitating interactions with outer membrane and then the plasma membrane of the cells [31]. Thus the mechanism of observed IL toxicity to the bacterial cells may be via membrane accumulation, disruption and subsequent increase of permeability of both cell wall and plasma membrane [32,33].…”