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.
Intellectual Merit We have engineered strains of bacteria that can transform renewable resources, like sugars and fats, into biodegradable plastics called polyhydroxyalkanoates (PHAs). There has been much interest in producing PHAs, because they can act as replacements for non-biodegradable, petroleum-based plastics. In addition, these materials are biocompatible and break down to metabolites that are naturally produced in the human body. Because of these traits, PHAs have potential to be used in biomedical applications such as drug delivery and tissue regeneration. A limiting factor to the widespread use of these materials is the ability to control the repeating unit composition of the polymers. This study identified proteins and pathways in the cells to produce PHA polymers with new and controlled repeating unit compositions that will allow us to customize the physical properties of the materials. Broader Impacts A number of broader impacts were achieved during the course of this project. Producing biodegradable and biocompatible plastic materials will have a great potential impact on society and sustainability. Personnel, including a postdoctoral researcher, graduate students, and undergraduate students were trained and supported by this project. In addition, this funding enabled a number of underrepresented and economically disadvantaged 5th – 10th graders were exposed to hypothesis-driven research through summer science sessions offered through the ESF SCIENCE and SOS programs at The State University of New York College of Environmental Science and Forestry (SUNY-ESF). This project has increased participation of a broad number of individuals in science and engineering research and will have a future impact on developing new technologies.
