KAIST Researchers Develop Microbial-Based Plastic with Potential to Replace PET Bottles

This breakthrough has been led by Distinguished Professor Sang Yup Lee of the Department of Chemical and Biomolecular Engineering, who, along with his team, has utilized advanced metabolic engineering to create a microbial strain capable of efficiently producing a sustainable alternative to PET.

Published in the Proceedings of the National Academy of Sciences, the study presents a novel microbial approach to producing pseudoaromatic dicarboxylic acids—compounds that offer superior physical properties and higher biodegradability compared to traditional aromatic polyesters like PET when synthesized as polymers.

The research addresses a significant limitation of previous chemical production methods for pseudoaromatic dicarboxylic acids, which were hindered by low yields, poor selectivity, complex reaction conditions, and hazardous waste byproducts. Using the bacterium Corynebacterium glutamicum, commonly employed in amino acid production, the KAIST team employed metabolic engineering to enhance the metabolic flow of protocatechuic acid, a precursor for various pseudoaromatic dicarboxylic acids, and prevent precursor loss.

Key Research Outcomes and Production Milestones

The KAIST team achieved remarkable production results, successfully synthesizing five types of pseudoaromatic dicarboxylic acids, each with potential roles in sustainable polymer production due to their biodegradability and physical properties:

2-pyrone-4,6-dicarboxylic acid: Produced at a global high concentration of 76.17 g/L, this compound serves as a biodegradable alternative monomer with potential applications in producing sustainable polyesters. Its high yield and physical stability make it a strong candidate for creating eco-friendly plastic materials to replace PET.

2,3-pyridine dicarboxylic acid: Produced at 2.79 g/L, this compound exhibits chemical properties that support stability in biodegradable polymer chains, which may enhance the durability and environmental friendliness of end products.

2,4-pyridine dicarboxylic acid: At a concentration of 0.49 g/L, this acid provides potential cross-linking capabilities, contributing to polymers with improved flexibility and resistance, suited for various packaging applications.

2,5-pyridine dicarboxylic acid: Produced at 1.42 g/L, this compound offers a balance of biodegradability and structural rigidity, making it suitable for lightweight applications where durability is required, such as single-use packaging or containers.

2,6-pyridine dicarboxylic acid: With a significant production yield of 15.01 g/L, this acid can potentially enhance the barrier properties of bio-based plastics, making it valuable for food and beverage packaging where protection from moisture or gas is essential.

Through transcriptome analysis, the team identified critical genetic targets, enhancing precursor retention and production efficiency. By introducing three new metabolic pathways for pyridine dicarboxylic acid production, the team significantly improved yields across all targeted acids, contributing to scalable production methods for sustainable polymer alternatives.

Industrial Applications and Future Potential

This pioneering work is expected to pave the way for various industrial applications in polyester production, providing a sustainable alternative to petrochemical-derived materials. The findings may contribute significantly to the future of bio-monomer production, ultimately reducing the chemical industry’s reliance on petrochemicals.

Professor Lee expressed optimism for the technology's future applications: "The significance lies in the fact that we have developed an eco-friendly technology that efficiently produces similar aromatic polyester monomers based on microorganisms. This study will help the microorganism-based bio-monomer industry replace the petrochemical-based chemical industry in the future."

For further details, refer to the original study: Jae Sung Cho et al., Metabolic engineering of Corynebacterium glutamicum for the production of pyrone and pyridine dicarboxylic acids, Proceedings of the National Academy of Sciences (2024). DOI: [10.1073/pnas.2415213121](https://doi.org/10.1073/pnas.2415213121).

Provided by: The Korea Advanced Institute of Science and Technology (KAIST)

Journal information: Proceedings of the National Academy of Sciences