Stability and activity of immobilised penicillin G amidase in ionic liquids at controlled aw

Despite the great interest in ionic liquids as novel solvents for biocatalysis, there is still no clear idea of their influence on the stability and the activity of enzymes. Here we analysed the activity and stability of PGA in six different ionic liquids, having different cations ([bmim] and [omim]) and anions (CH3OSO3 2, PF6 2 and BF4 2). To be active in ionic liquids, PGA-450 requires an acceptable hydration (aw . 0.60), as in organic solvents. PGA is highly stable in [bmim][PF6] and [bmim][BF4], and catalytic activity, assayed by studying the synthesis of the amide of L-phenylglycine methyl ester with methyl phenylacetate, in these ILS is comparable to that obtained in toluene.