Polyhydroxyalkanoates (PHAs) are microbially produced, biobased, and biodegradable polymers that have a wide array of uses ranging from substitutes for non-biodegradable, petroleum-based plastics in bulk commodity products to biomedical applications. One of the factors that limits the widespread use of PHAs for more specialized applications is the lack of control over repeating unit compositions and by extension the inability to produce polymers with desired physical properties. The long-term goal of this research project is to genetically engineer E. coli for producing expanded classes of PHA materials with desirable material properties. PHAs comprised of repeating units of 3-5 carbon atoms are known as short-chain-length PHAs (SCL-PHAs) and tend to be thermoplastic in nature but lack toughness, while PHAs comprised of repeating units of 6-14 carbon atoms are known as medium-chain-length PHAs (MCL-PHAs) and tend to be elastomeric. It has been demonstrated in previous studies that SCL-MCL PHA copolymers that are comprised of 80-95% SCL and 5-20% MCL repeating units have material properties that are very similar to common petroleum-based plastics. The objective of this project is to further develop strains so that they can produce SCL-MCL PHA and PHA-co-Polylactic acid (PLA) copolymers with desirable material properties from the renewable sugar feedstocks, and to produce new PHA-co-PLA copolymers with specific repeating unit compositions from lactic acid and fatty acids. This will be accomplished with a combination of synthetic biology, metabolic engineering, protein engineering, and synthetic chemistry methods to improve PHA production. Successful completion of these studies will lead to novel polymer production platforms with the potential to overcome the lack of diversity and control over repeating unit compositions of existing bacterial PHA producing systems and expand the number of applications for PHA polymers.
The proposed studies and research training activities are expected to have a broad impact on society, ranging from improving upon the science of biodegradable and biobased polymer synthesis to the development of new biomaterials for research, industrial, and biomedical applications. The project will contribute to reduce US dependency on non-renewable sources such as fossil fuels for energy, materials production, and transportation. The research associated with this proposal is intrinsically interdisciplinary in nature and will be performed in a diverse training environment. It will also provide summer research experiences for underrepresented minority students with a goal of increasing the number of college graduates from groups that are traditionally underrepresented in science and engineering.
Due to the interdisciplinary nature of this SusChEM project the award from the Biotechnology, Biochemical, and Bioengineering Program of the CBET Division is co-sponsored by the Genetic Mechanisms Program of the Molecular and Cell Biology Division and by the Biomaterials Program of the Division of Materials Research.
