Biological Synthesis and Materials Properties of Bacterial Polyesters

提出的研究计划将阐明细菌在细胞内合成储备聚酯及其细胞内和细胞外解聚酶的分子和超分子过程。该计划的具体目标包括：(1)了解细胞运输过程和生化反应，涉及利用：(a)生长良好的聚合物生产基质，(b)生长良好的非生产基质，以及(c)非生长基质，特别是在(a)+(b)和(a)+(c)混合物的共代谢中，通过(a)+(b)和(a)+(c)产生非生产基质(b)和(c)的共聚物；(2)了解颗粒内聚合物形成的酶促过程，特别是聚合酶的数量、活性和位置，以及分离颗粒参与细胞外聚合反应的能力；(3)了解解聚合酶与单个聚合物分子之间的相互作用，特别是在固体表面上。该计划的其他目标包括以下内容：(i)制备全新的非天然聚酯，并评估其材料特性（包括生物降解性）作为塑料或弹性体；（ii）以聚合物生产为模型系统，促进对共代谢生物化学的基本理解；（iii）分离和表征细菌和真菌分泌的细胞内聚合酶和解聚合酶，这些酶可以利用这些聚酯作为生长底物在自然环境中进行生物降解。聚酯已被证明是一种用途非常广泛的热塑性塑料，在许多工业产品中得到广泛应用。它们可以制成薄膜、纤维和模塑产品。聚酯也可以用于包装以及纯形式，或与羊毛，棉花等混纺，作为服装材料。这些由石油化学生产的产品为工业和医疗用途提供了许多有用的，甚至是必要的产品。然而，由于它们是从石油蒸馏液中合成的有机化学物质，它们在任何已知的现有工艺中都不能生物降解，因此这些产品的废物处理在世界范围内是一个日益严重的问题。具有相同化学组成和性质的聚酯可由大量细菌制成。因为它们是由细胞内的酶合成的，而不是化学合成的，所以它们产生的是完全可生物降解的立体规则聚合物。从本质上讲，这些细菌以生物合成聚酯为食物。理论上，这些聚酯可以像处理任何有机废物一样处理。我们将对这些新生物材料的酶降解机制进行研究。此外，我们已经证明，这些细菌或“天然”聚酯具有许多化学合成无法复制的新的和潜在的特性。例如，我们发现了一种细菌，它可以合成一种聚酯，它是一种弹性体，也就是说，它的行为像橡胶。在许多产品的生产中使用这种产品-例如可生物降解的外科手套或带有可生物降解塑料衬垫的尿布-将是解决塑料废物处理问题的一大进步。

The proposed research program would elucidate the molecular and supermolecular processes involved in the intracellular synthesis of reserve polyesters by bacteria and their intracellular and exocellular depolymerization by enzymes. Specific goals of the program include: (1) an understanding of the cellular transport processes and biochemical reactions involved in the utilization of: (a) good-growth good-polymer producing substrates, (b) good-growth non-producing substrates, and (c) non-growth substrates, especially in the cometabolism of mixtures of (a)+(b) and of (a)+(c) by which the coploymers from the non-productive substrates, (b) and (c), are produced; (2) an understanding of the enzymatic processes involved in polymer formation within the granule, especially the number, activity and location of the polymerase enzymes and the ability of isolated granules to participate in extracellular polymerization reactions; (3) an understanding of the interaction between depolymerase enzymes and individual polymer molecules, especially on solid surfaces. Additional goals of the program include the following: (i) to prepare entirely new, non-natural polyesters and evaluate their materials properties (including biodegradability) as plastics or elastomers; (ii) to contribute to the basic understanding of the biochemistry of cometabolism by using polymer production as a model system; and (iii) to isolate and characterize the intracellular polymerase and depolymerase enzymes excreted by bacteria and fungi that can utilize these polyesters as growth substrates in their biodegradation in natural environments. %%% Polyesters have proven to be extremely versatile thermoplastics in wide use in many industrial products. They can be fabricated into films, fibers and molded products. Polyester can also be used for packaging as well as in pure form, or when blended with wool, cotton, etc., for clothing material. These products produced chemically from petroleum provide many useful and indeed necessary items for industrial and medical uses. However, because they are synthetic organic chemicals from petroleum distallates, they are not biodegradable in any known current process and waste disposal of these products is an increasing problem world wide. Polyesters of identical chemical makeup and properties can be made by a large number of bacteria. Because they are made by enzymes in cells as opposed to chemical synthesis, they produce stereoregular polymers which are fully biodegradable. Essentially, these bacteria use biosynthetic polyesters as food. Theoretically these polyesters can be treated for disposal like any organic waste. We will be undertaking a study of the enzymatic mechanisms of degradation of these new biomaterials. In addition we have shown that these bacterial or "natural" polyesters have many new and potential properties that cannot be duplicated by chemical synthesis. For instance we have discovered a bacterium that can synthesize a polyester that is an elastomer, i.e. it behaves like rubber. The use of such a product in the production of many items-- surgical gloves for example that are biodegradable or diapers with biodegradable plastics liners would be a big advance in solving the plastic waste disposal problem.