Suitability of non-conventional reaction medium for biocatalysis: From lipase activity to thermophysical characterization

Abstract

This work is focused on the demonstration of the ability of DES composed of choline chloride (ChCl) as hydrogen bond acceptor (HBA) and urea and/or glycerol as hydrogen bond donors (HBD) to be employed as biocatalytic milieu in Candida antarctica lipase B (CALB)-catalysed biodiesel production. Not only, the biocatalytic activity was maintained in the presence of common acyl acceptors like alcohols (methanol, ethanol and 1-propanol), but also the use of a ternary DES (ChCl:urea:glycerol) entailed a drastic activation of the enzyme regarding the biocatalytic potential in water. The necessity of characterizing the DES became evident, so different physical properties like density, refractive indices, speed of sound and dynamic viscosity were determined at temperatures comprised between (298.15 and 343.15) K and 0,1 MPa. in order to unravel the possible chemical interactions of DES with enzymes. Besides, several derived magnitudes like the molar volume, isentropic compressibility, isobaric thermal expansion, intermolecular free length, molar refraction, free volume, and internal pressure were determined together with the critical volume, critical temperature, critical pressure, boiling point and acentric factor. It was concluded that some properties like density, refractive index and dynamic viscosity or derived magnitudes like the molar volume and the free volume were useful tools to rationalize the interaction of DES with lipases.