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ABSTRACT – Industrially, amoxicillin has been produced by chemical processes. But, the enzymatic synthesis catalyzed by penicillin G acylase (PGA, E.C.3.5.1.11) is more attractive from the environmental point of view. However, an obstacle for the industrial application of the enzymatic route is the limited product yield due to undesirable hydrolytic reactions. This drawback can be minimized by reducing water activity in the reaction medium. Ionic liquids (ILs) have emerged as an alternative to conventional organic media. This study assessed the feasibility of use of different ILs, protic (PILs) and aprotic (AILs), in the enzymatic synthesis of amoxicillin, by testing the stability of reaction substrates (6-aminopenicillanic acid and p-hydroxyphenylglycine methyl ester) in these solvents. These compounds were completely stable in AILs. Besides, PGA was active in AILs. In contrast, none of the evaluated PILs was inert for these substrates making unfeasible the use for this enzymatic process. 1