In a significant leap toward sustainable materials science, researchers have engineered a bio-based polyester with exceptional toughness and biodegradability by enhancing the expression of a key lactate-polymerizing enzyme. This development heralds a transformative approach for replacing conventional petroleum-derived plastics with environmentally friendly alternatives capable of addressing mounting ecological crises.
The polymer at the center of this breakthrough is poly[(D-lactate)-co-(R)-3-hydroxybutyrate], commonly referred to as LAHB. LAHB is a microbial copolyester synthesized by bacteria and recognized for its unique ability to combine mechanical strength with rapid biodegradability. Notably, the ratio of lactate (LA) units within the polymer chain critically influences the material’s physical characteristics, dictating its balance of toughness and flexibility.
Traditional attempts to boost the lactate content in LAHB encountered challenges in maintaining high molecular weight—a vital factor underpinning polymer durability. To overcome these obstacles, a multidisciplinary team led by Professor Seiichi Taguchi at Shinshu University introduced an innovative genetic engineering strategy. They reinforced the gene expression of the lactate-polymerizing enzyme (LPE) in the recombinant bacterium Cupriavidus necator, a well-known workhorse for bioplastic production.
By inserting an LPE-expressing plasmid vector named pCUP-lacUV5-LPE into a specific C. necator strain (GS3 series) via electroporation, the researchers elevated the enzyme activity responsible for incorporating lactate units into the growing polymer chain. This enhancement facilitated an unprecedented increase in LA fraction without compromising the molecular weight, achieving a delicate equilibrium essential for real-world applications.
Fermentation experiments using fed-batch culture with controlled glucose feeding revealed remarkable production metrics. The engineered strain GSXd147 accumulated dry cell weights of 97 g/L enriched with 70 wt% of LAHB within 48 hours. This corresponds to an LAHB titer of 68 g/L—the highest reported to date—alongside an impressive molecular weight of Mw 30 × 10^4 and a lactate content reaching 15.4 mol%.
Mechanical evaluations underscored the advancement offered by this high-molecular-weight LAHB. Films produced exhibited a tensile strength of approximately 20 MPa combined with an elongation at break near 190%, placing their performance on par with conventional polyethylene plastics. This balance is unusual in biodegradable plastics, which typically favor either flexibility or strength at the expense of the other, highlighting LAHB’s unique value proposition.
Further cementing its environmental credentials, both high- and low-molecular-weight LAHB variants demonstrated substantial biodegradation in marine seawater, achieving over 75% breakdown within five weeks, as measured by biochemical oxygen demand. Importantly, degradation rates remained consistent regardless of molecular weight, confirming that toughness enhancements do not deter eco-friendly degradation—a crucial feature for mitigating plastic pollution in aquatic ecosystems.
This study not only exemplifies how tailored bioengineering can resolve enzymatic bottlenecks in bioplastic synthesis but also lays the foundation for industrial-scale production of high-performance, biodegradable polymers. By directly addressing the trade-offs between mechanical robustness and environmental compatibility, it pushes forward the paradigm of sustainable materials science.
The implications extend beyond scientific novelty, offering tangible solutions to reduce the pervasive problem of microplastics by replacing standard plastics with next-generation biopolymers that balance utility and eco-safety. LAHB’s unique composition and biodegradability profile make it poised to benefit an array of industries seeking greener raw materials without sacrificing quality or durability.
Moreover, the research highlights the vital role of synthetic biology in enhancing microbial production pathways, demonstrating that genetic modification can be harnessed to overcome intrinsic material limitations. The strategic overexpression of LPE marks a critical step in optimizing LAHB synthesis, illustrating the power of systems biology combined with advanced fermentation techniques.
As global plastic pollution threatens ecosystems and human health, innovations such as LAHB provide a hopeful avenue for decoupling economic growth from environmental degradation. This study, published in the journal Polymer Degradation and Stability, stands as a testament to interdisciplinary collaboration and the potential of bio-based polymers to transform the materials landscape.
Looking forward, further optimization and scale-up of this technology could accelerate the implementation of biodegradable plastics in commercial markets, promoting circular economy principles. By harnessing the metabolic versatility of microorganisms and precision gene editing, the pathway toward sustainable, high-performance plastics is becoming clearer and more achievable.
The groundbreaking work by Professor Taguchi and his colleagues not only addresses pressing environmental challenges but also opens new frontiers in polymer science, marrying molecular biology with materials engineering to create the next generation of sustainable plastics.
Subject of Research: Not applicable
Article Title: Tough and biodegradable lactate (LA)-based polyester (LAHB) hyperproduced by reinforcing LA-polymerizing enzyme gene expression
News Publication Date: 1-Apr-2026
Web References:
https://doi.org/10.1016/j.polymdegradstab.2025.111910
Image Credits: Professor Seiichi Taguchi from Shinshu University, Japan
Keywords: Biodegradable plastics, Polyesters, Synthetic biology
