Synthesis of polyester using enzyme-catalyzed polymerization

研究表明，水解酶促进了多用途型单体聚酯和聚碳酸酯的聚合。使用水解酶生产聚合物的优点之一是聚合和解聚之间的可逆反应。本研究涵盖了可生物降解的脂肪族聚酯和聚碳酸酯的酶催化聚合和化学回收，特别是建立绿色高分子化学。发现单体的底物特异性受到水解酶来源的显著影响。也就是说，四元内酯很容易被PHB解聚合酶聚合。另一方面，中、大元内酯容易被脂肪酶聚合。采用固定化脂肪酶在含少量水的有机溶剂中将聚己内酯（PCL）、聚3-羟基烷烃酸酯（PHA）、聚乳酸（PLA）、聚烷基烯二酸酯（alkylene alkanediate）和聚碳酸三亚甲基（trimethylene carbonate）等典型的可生物降解聚酯解聚为相应的环状低聚物。所得的低聚物分子量为几百，可以用脂肪酶和常规化学催化剂进行聚合。超临界二氧化碳也是脂肪酶催化这种聚酯解聚成可再聚合的环状低聚物作为有机无溶剂体系的适当反应介质。用固定化脂肪酶柱在有机溶剂中连续酶降解脂肪族聚酯为环低聚物。PHA、PCL和聚己二酸丁二烯在40℃甲苯溶液中通过固定化脂肪酶填充的酶柱，很容易解聚成相应的环状低聚物。这些结果表明，即使在聚合物工业中，使用生物催化剂也可以实现可持续的聚合物生产系统。

It has been revealed that the hydrolase enzyme promoted the polymerization of versatile types of monomer forming polyesters and polycarbonates. One of the advantages of using a hydrolase enzyme for polymer production is the reversible reaction between polymerization and depolymerization. This study covers the enzyme-catalyzed polymerization and chemical recycling of biodegradable aliphatic polyesters and polycarbonates particularly highlighted for establishing green polymer chemistry. It was found that substrate specificity for the monomers was significantly influenced by the hydrolase enzyme origin. That is, four-membered lactones were readily polymerized by PHB depolymerase. On the other hand, medium and large-membered lactones were readily polymerized by lipase. Typical biodegradable polyesters, such as polycaprolactone (PCL), poly (3-hydroxyalkannoate) (PHA), polylactate (PLA), poly (alkylene alkanedioate) and poly (trimethylene carbonate), were depolymerized into the corresponding cyclic oligomers by using the immobilized lipase in an organic solvent containing a small amount of water. The obtained oligomer having a molecular weight of a few hundreds could be polymerized both by the lipase and conventional chemical catalyst. Supercritical carbon dioxide was also an adequate reaction medium for the lipase-catalyzed depolymerization of such a polyester into the repolymerizable cyclic oligomer as an organic solvent-free system. The continuous enzymatic degradation of aliphatic polyesters into cyclic oligomers was carried out using an immobilized lipase column in an organic solvent. PHA, PCL and poly (butylene adipate) were readily depolymerized into the corresponding cyclic oligomers by passage through the enzyme column packed with immobilized lipase using a toluene solution at 40℃. These results imply that even in the polymer industry, a sustainable polymer production system will be realized using biocatalysts.