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.
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