PHA Biosynthesis DBTL Acceleration

The goal of bio-manufacturing research is to accelerate the design-build-test-learn (DBTL) cycle of PHA biosynthesis in conjunction with the upstream biorefinery, as well as the downstream composites manufacturing and product end-of-life plan. To achieve the goal, this project focuses on the integration of synthetic biology, metabolic engineering, systems biology, and machine learning. An industrially relevant PHA producer, Cupriavidus necator, is employed as the primary microbial host platform. The produced PHAs will be extracted and recovered and tested for composites manufacturing and 3D/4D printing applications.

Strain Development Acceleration

Goal 1 focuses on developing synthetic biology toolkits to accelerate strain development. The two desirable PHA production parameters are high molecular weight and production metrics (i.e., titers, yields, and production rates), which are often interconnected through the convoluted metabolic network. The objective is to develop high-throughput genetic engineering and PHB quantification methods to address the challenge.

Strain Design and Construction

Goal 2 explores design and construct high-performing strains and optimize fermentation processes. C. necator has the capability of utilizing carbon dioxide (CO₂) along with fermentable sugars or carboxylic acids, potentially enabling carbon-neutral fermentation with improved carbon efficiency. The metabolic capabilities need to be leveraged to develop a ‘net-zero’ PHA production process. The cost-efficient PHA production heavily relies on the microbial cell performance, requiring a strain that can co-utilize a broad range of carbon sources along with robustness toward inhibitory compounds derived from lignocellulosic feedstocks. The objective is to design and construct high-performing strains capable of co-utilizing lignocellulosic hydrolysates and CO₂ gas.

Copolymerization

Goal 3 is focused on fine-tuning physicochemical properties of PHA through copolymerization. PHA copolymers often have better physicochemical properties compared to PHB homopolymer. Production of the PHA copolymers can better harness the modularity of PHA based composites manufacturing. The objective is to further manipulate microbial PHA production to synthesize PHA copolymers, poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx).

Microbial Conversion Platform Development

This research aims to develop an advanced microbial conversion platform for producing polyhydroxyalkanoates (PHAs), biodegradable polymers derived from renewable resources. By leveraging synthetic biology, metabolic engineering, and machine learning, the project focuses on engineering microbial strains and optimizing fermentation processes to produce PHAs with tailored physicochemical properties. These biopolymers will be designed for applications in composite manufacturing, 3D/4D printing, and sustainable packaging. The integration of cutting-edge biotechnologies will enable a scalable and eco-friendly approach to bioplastic production, contributing to a circular bioeconomy and reducing reliance on petroleum-based plastics.

PHA Composites Development

Goal 1 focuses on developing optimal composition and processing conditions of PHA composites for 3D/4D printing filaments. PHB, a type of PHA, displays brittleness and low impact strength due to its high crystallinity, limiting its applications. By introducing polymer blending and composite fabrication techniques, crystallinity of PHB can be optimized through intermolecular interactions and can be mechanically reinforced with inclusion of bio-fillers. For scalable and flawless production of polymer blends and their composites, optimal processing conditions such as temperature, shear rate, composition ratio, and rheological properties for 3D printability must be defined and controlled. The team will attain such objectives by sequentially expanding the scope of experiments: gram-scale batch compounding to kg-scale continuous extrusion; commercial PHA to GCSB’s PHA products; and plain polymer blends to multi-modal complexes of polymer composites.

Biocomposite Product Structural Characterization

Goal 2 focuses on structural characterization of biocomposite products using synchrotron X-ray and macroscopic mechanical testing. This study will evaluate the effects of blending different PHAs on modifying crystallinity, while bio-based fillers enhance mechanical properties of PHA composites. By analyzing the crystalline structure, filler dispersion, and void defects, the team seeks to establish structure-property relationships that inform optimal formulations. Advanced techniques such as X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and synchrotron small-angle X-ray scattering (SAXS) will provide insights at multiple scales. Additionally, mechanical evaluations using a universal testing machine (UTM) will assess tensile strength, modulus, and toughness. Our findings here will contribute to the rational design of high-performance, bio-based composites.