Polycondensation of α-Hydroxy Acids by Enzymes or PEG-Modified Enzymes in Organic Media

Abstract

Abstract In order to provide biodegradable poly(hydroxy acid)s by a simple process, fundamental studies on the polycondensation of α-hydroxy acids by enzymes and polyethylene glycol (PEG)-modified enzymes in organic media were carried out. The oligomer formation by unmodified hog liver esterase proceeded well using glycolic acid as a substrate in cyclohexanone. Lipase from Aspergillus niger gave the best result for the polycondensation of glycolic acid among the unmodified enzymes used. The effects of the PEG-modification of enzyme on the polycondensation of α-hydroxy acids are also discussed. When the enzyme modified with a small amount of low-molecular-weight PEG was used, the conversion by polycondensation was relatively high. In particular, by using ethyl glycolate as a substrate, which allows an ester exchange reaction, and 1,4-dioxane as a solvent, polycondensation by PEG-modified enzyme proceeded effectively to give the pentamer of poly(glycolic acid).