Synthesis of aliphatic polyesters via methyl hydroxy acid polycondensation catalyzed by lipase candida sp.99-125

Several hydroxyl acid esters were successfully converted into aliphatic polyesters catalyzed by free lipase Candida sp.99-125 without organic solvents. The polycondensation of methyl 6-hydroxycaproate was selected as a model process in this study. The effects of different conditions including catalyst dosage, monomer purity, temperature and surfactant on the reaction were studied. The results show that aliphatic polyesters can be synthesized with minimum monomer purity of 95% under solvent-free conditions. Tween 40 and Tween 80 can narrow molecular weight distribution and increase weight-average molecular weight. Moreover, the enzyme maintains activity up to five rounds, and lipase shows a high selectivity for monomers with long chain under the optimal conditions. The weight-average molecular weight can be adjusted in a range of 3200 to 10000 Da by changing monomer carbon chain length.