Mechanism and applications of Novozyme435-catalyzed polyesters synthesis.

摘要

Novozyme435, the lipase B from Candida antarctica (CALB) immobilized on polyacrylate resin, was characterized by synchrotron IR Microspectrascopy (SIRMS) to provide information about the enzyme distribution and secondary structure. SIRMS imaging revealed that the enzyme is unevenly localized in an external shell of the bead with a thickness of 80--100 mum. Furthermore, by SIRMS generated spectra, it was found that the CALB secondary structure was not altered by immobilization.; Polymerizations of epsilon-caprolactone (epsilon-CL) catalyzed by Novozyme435 were studied at temperatures between 20°C and 108°C. The monomer conversion to polymer was remarkably rapid over the whole temperature range. Contrary to previous reports, the number of chains formed, as well as the product molecular weight, was almost identical for polymerizations at constant enzyme water content between 60 and 108°C. Thus, differences in reaction temperature over a 48°C range did not "free" water from "bound" states so that it could function for chain initiation. Different polymerization kinetics were found at different reaction temperatures with a series of initial enzyme water contents.; Kinetic studies on Novozyme435-catalyzed caprolactone polymerization revealed that the monomer activation step is the rate determine step. The apparent activation energy for the polymerization in toluene is 2.88 kcal mol-1, well below 10.3 kcal mol-1, the activation energy for aluminum alkoxide catalyzed epsilon-CL polymerization in toluene. An upward deviation from linearity in plot of M n versus fractional epsilon-CL conversion and decreases in the number of chains was accentuated by low enzyme water contents and high monomer conversion. These results are consistent with a competition between ring-opening chain-end propagation and chain growth by step-like polycondensations.; A series of sorbitol-containing polyesters were synthesized via a one-pot Novozyme435-catalyzed condensation polymerization. Their surface properties and cell response were analyzed and results establish the sorbitol-containing polyester series as a promising material for tissue engineering research and development.