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项目颁发，旨在通过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，研究聚羟基烷酸酯（pha）单体供应的改善。pha是微生物产生的、生物基的、可生物降解的聚合物，具有与石油基聚合物相似的特性。用pha替代石油基塑料可以减轻许多与不可生物降解塑料有关的污染问题。PHA聚酯可根据其单体组成分为具有不同物理性质的几类。短链长度（SCL）相has由3-5个碳的重复单元组成，具有热塑性性能。中链长度（MCL）相has由6-12个碳的重复单元组成，具有弹性体性质。SCL-MCL相体由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单体供应酶活性低，在重组生物中从不相关的碳源生产MCL和SCL-MCL PHA聚合物的能力受到限制。研究的主要目标有两个：(1)利用工程细菌的合成代谢途径，从不相关的碳源高效地生产SCL和MCL共聚物；(2)改变底物特异性和酶的比活性，以供应PHA单体以生产新的共聚物配方。利用随机、易出错的PCR和基于已知酶晶体结构的合理设计的酶工程将用于生产改进的PHA单体供应酶，用于生产新的可生物降解聚合物。塑料是一种无价的材料，被用来生产现代社会的许多必需品。目前大多数塑料来自石油，这是一种有限的资源。与石油基塑料有关的许多问题（污染、废物处理问题、温室气体排放、竞争性燃料利用等）表明，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？微生物工厂吗?利用可再生的植物资源生产可生物降解的塑料。通过在细菌内设计蛋白质，我们将能够生产出更多的生物基塑料，并生产出具有改进材料性能的新型生物基塑料。这项工作将为生物降解塑料是如何在细胞中产生的提供新的和详细的见解。拟议研究的完成可能会对减少由石油基塑料引起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.