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Abstract: A novel lipase-catalyzed synthesis of aliphatic polyesters has been achieved successfully by using Candida sp.99-125 with diethyl sebacate and 1,4-butanediol as starting substrates in absence of organic solvents. The lipase from Candida sp.99-125 was employed for the first time to catalyze synthesis of poly(butylene sebacate) and showed high catalytic activity for bulkpolymerization under mild reaction conditions. The eco-friendly processes, without any environmental pollution, avoided both phase separation of the reactants and the use of toxic solvents effectively. The polycondensation reactions were performed in two stages: first stage reaction under atmospheric pressure to convert the monomers to oligomers followed by second stage reaction under vacuum process, with a highest molecular weight of 15,800 obtained in molar ratio of 1:1 at 70°C. The corresponding polyesters determined by thermogravimetric analysis (TGA) were much thermally stable up to 300°C. Differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXS) analysis demonstrated the polymers had a strong ability to crystallize with the degree of crystallinity up to 66%. [Copyright &y& Elsevier]