Effect of ionic liquids as additives in the catalytic properties of different immobilized preparations of Rhizomucor miehei lipase in the hydrolysis of peracetylated lactal

Abstract

The addition of small amount of different ionic liquids modified the activity and regioselectivity of different immobilized preparations of R. miehei lipase catalyzing the hydrolysis of hexa-O-acetyl lactal in aqueous media. ILs with [emim] as cation and different anions were first evaluated affecting in a different manner depending on the immobilized preparation used. The enzymatic activity of RML immobilized on octyl-agarose or CNBr-agarose decreased in the following order: NO₃⁻≈ BF₄⁻ > MeOSO₃⁻ > PF₆⁻, whereas when RML was immobilized on Q-Sepharose, the enzymatic activity decreased in a different order: MeOSO₃⁻ > PF₆⁻ > BF₄⁻ > NO₃⁻. Using [bdmim], the activity of octyl-RML and CNBr-RML preparations resulted higher in the presence of PF₆⁻ than BF₄⁻, 6-fold for octyl-RML and 2-fold for CNBr-RML if compared with the enzyme activity without additive_. In both preparations the enzyme was completely regioselective in the presence of the IL hydrolyzing at C-3 position in 99% yield. The modification of the cation in the IL did not affect to the activity of Q-RML with BF₄⁻ or decreased the activity with PF₆⁻, although affected to the regioselectivity producing another undesired product, a bihydrolized product in 20–25% yield. In this case, the addition of [emim][MeOSO₃] caused the best increment in the activity for this RML biocatalyst, 2-fold with only 8% of bihydrolized production.