Protein and Metabolic Engineering for the Production of Biodegradable Plastics

该奖项由纽约州立大学环境科学与林业学院材料研究部生物材料计划颁发，旨在通过将体外进化技术应用于编码微生物脂肪酸生物合成酶的基因来研究聚羟基烷酸酯(PHAs)单体供应的改善。PHA是微生物生产的、基于生物的、可生物降解的聚合物，具有类似于石油聚合物的性质。用PHAs取代石油基塑料可以缓解许多与不可生物降解塑料有关的污染问题。PHA聚酯按其单体组成可分为几类，具有不同的物理性能。短链(SCL)PHA由3-5个碳的重复单元组成，具有热塑性。中等链长(MCL)的PHA由6-12个碳的重复单元组成，具有弹性性质。SCL-MCL PHA由4-12个碳的重复单元组成，具有广泛的物理性质，这取决于它们的SCL与MCL单体的摩尔比。目前，由于潜在的MCL单体供给酶活性较低，从重组生物中无关的碳源生产MCL和SCL-MCL PHA聚合物的能力受到限制。拟议的研究有两个主要目标：(1)利用含有合成代谢途径的工程菌，从无关的碳源高效地生产SCL和MCL共聚物；(2)改变底物专一性和酶的比活性，以供应PHA单体，以产生新的共聚物配方。利用随机的、容易出错的聚合酶链式反应和基于已知的酶的晶体结构的合理设计的酶工程将被用于生产改进的PHA单体供应酶来生产新型的可生物降解聚合物。塑料是无价的材料，用于生产现代社会中的许多必需品。目前大多数塑料都是从石油中提取的，石油是一种有限的资源。与石油塑料有关的问题很多(污染、废物处理问题、温室气体排放、燃料竞争利用等)，这表明在生物基和可生物降解替代品领域的研究至关重要。这项研究支持的研究将使用细菌作为微生物工厂？用于从可再生的植物资源中生产可生物降解的塑料。通过在细菌中改造蛋白质，我们将能够生产更大量的生物基塑料，并生产具有更好材料性能的新型生物基塑料。这项工作将为可生物降解塑料是如何在细胞中生产的提供新的和详细的见解。这项拟议研究的完成可能会对减少石油塑料造成的各种城市污染问题产生巨大影响。

This award by the Biomaterials program in the Division of Materials Reseach to State University of New York, College of Environmental Science and Forestry is to study the improvements of polyhydroxyalkanoates (PHAs) monomer supply through the application of in vitro evolutionary techniques to genes encoding microbial fatty acid biosynthetic enzymes. PHAs are microbially produced, biobased, and biodegradable polymers that have properties similar to petroleum-based polymers. Substitution of petroleum-based plastics with PHAs could alleviate many of the pollution problems associated with non-biodegradable plastics. PHA polyesters can be divided into several classes with different physical properties based on their monomer composition. Short-chain-length (SCL) PHAs consist of repeating units with 3-5 carbons and have thermoplastic properties. Medium-chain-length (MCL) PHAs consist of repeating units with 6-12 carbons and have elastomeric properties. SCL-MCL PHAs consist of repeating units of 4-12 carbons and have a wide range of physical properties dependent on their molar ratio of SCL to MCL monomers. Currently, the ability to produce MCL and SCL-MCL PHA polymers from unrelated carbon sources in recombinant organisms is limited due to low activity of potential MCL monomer-supplying enzymes. There are two main objectives for the proposed research: (1) Use of engineered bacteria harboring synthetic metabolic pathways to efficiently produce SCL and MCL copolymers from unrelated carbon sources; and (2) the alteration of the substrate specificity and specific activity of enzymes for the supply of PHA monomers to produce novel copolymer formulations. Enzyme engineering using random, error-prone PCR and rational design based on known crystal structures of enzymes will be used for the production of improved PHA monomer-supplying enzymes for the production of novel biodegradable polymers.Plastics are invaluable materials that are used to produce many essential items in modern society. Most current plastics are derived from petroleum, which is a limited resource. There are many problems associated with petroleum-based plastics (pollution, waste disposal problems, greenhouse gas emission, competitive fuel utilization, etc.), which suggest that research in the area of biobased and biodegradable alternatives is of paramount importance. Studies supported by this research will use bacteria as ?microbial factories? for the production of biodegradable plastics from renewable, plant-based resources. By engineering proteins within the bacteria, we will be able to produce higher quantities of biobased plastics and produce new types of biobased plastics with improved material properties. The work will yield new and detailed insights into how biodegradable plastics are produced in cells. Completion of the proposed research could have dramatic impacts on curtailing a variety of urban pollution issues caused by petroleum-based plastics.