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M. Kato, K. Toshima, and S. Matsumura^1,*

 Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522, JAPAN

Keywords: Enzyme-catalyzed polymerization, polythioesters, lipase, mercaptoalkanoic acid, degradation

Microbial polyesters containing thioester linkages in their backbone were recently reported by Lüke-Eversloh and Steinbüchel et al. for the first time and comprise a novel class of biopolymer. Microbial homopolymers of polythioester show some unique characteristics such as high melting point and poor solubility against various solvents. The synthetic polythioester has been reported fifty years ago, but commercial production of the polythioester has not been established partially due to the complex preparation methods. In this report, a more straightforward method, the novel lipase-catalyzed preparation of polythioester by the polymerization of 11-mercaptoundecanoic acid (11MU) and its transformation into cyclic oligomers is described.

11MU was polymerized by using immobilized lipase from Candida antarctica (lipase CA) to afford poly(11MU). As a typical example, poly(11MU) having an M_w of 31,000 was obtained quantitatively by lipase CA at 110 °C in bulk for 3 days under the existence of molecular sieves 4Å as a water absorbent. This is the first example to obtain a relatively high molecular weight homopolythioester using an enzyme. The thermal properties of poly(11MU) have been compared with those of poly(11-hydroxyundecanoic acid) to evaluate the effect of the thioester linkages in the polymer backbone.

The obtained poly(11MU) was readily degraded by lipase CA at 110 °C in n-octane to produce the corresponding cyclic oligomers having a molecular weight of few hundreds. The degradation was mainly dependent on reaction conditions such as polymer concentration, organic solvent, and reaction temperature. The repolymerization of these oligomers was also studied. Based on these results, it is highly expected that this type of novel polymer can be chemically recycled by using the reversible reaction of the enzyme.

論文來源：International Symposium on Biological Polyesters ,Auguest 22-27, 2004