- Biodegradable polymer produced from glucose-fed E. coli

- Adhesive strength 9% higher than conventional products; heat resistance and re-adhesion improved

From left: Kang Min-ju, a doctoral candidate in the Department of Chemical and Biomolecular Engineering at KAIST; Distinguished Professor Lee Sang-yup; and researchers Lee Young-jun and Kim Ki-bae. [KAIST]
From left: Kang Min-ju, a doctoral candidate in the Department of Chemical and Biomolecular Engineering at KAIST; Distinguished Professor Lee Sang-yup; and researchers Lee Young-jun and Kim Ki-bae. [KAIST]

South Korean researchers have developed a technology to produce adhesives using E. coli instead of petroleum. A bio-based polymer derived from glucose-fed E. coli has demonstrated higher adhesive strength than conventional petroleum-based adhesives.

KAIST announced Thursday that a research team led by Distinguished Professor Lee Sang-yup of the Department of Chemical and Biomolecular Engineering has developed a "microbial cell factory" capable of producing high-performance adhesive materials from glucose by precisely engineering the genetic and metabolic pathways of E. coli.

Hot-melt adhesives — widely used in everything from delivery boxes and furniture to electronics and automobiles — work by melting when heat is applied and solidifying when cooled to bond objects together. They currently rely mainly on petroleum-derived polymers such as ethylene-vinyl acetate (EVA). These materials do not break down easily in nature, however, posing risks of waste accumulation and microplastic pollution.

The research team turned its attention to polyhydroxyalkanoate (PHA), a biodegradable polymer that microorganisms can produce from renewable raw materials.

The key challenge was improving both adhesive strength and heat resistance at the same time. The team combined 4-hydroxybutyrate (4HB), which makes the material soft and sticky, with phenyllactate (PhLA), which enhances rigidity and heat resistance. By adjusting the ratio of the two components, the researchers achieved the desired material properties.

To accomplish this, they redesigned the metabolic pathways inside E. coli and optimized gene expression and enzyme activity. A computer-based metabolic model was also used to resolve bottlenecks in the production process.

As a result, the team successfully produced 10.2 grams of the new polymer — poly(4HB-co-PhLA) — per liter of culture medium. A variant incorporating an additional component, 3HB, pushed output to 52.8 grams per liter.

The adhesive performance also surpassed that of existing commercial products.

A schematic summary of the research. [KAIST]
A schematic summary of the research. [KAIST]

In shear adhesion tests on stainless steel, the newly developed polymer recorded an adhesive strength of 4.58 megapascals — about 9 percent higher than commercial EVA adhesive at 4.20 megapascals. In wood adhesion tests, another bio-based polymer variant performed at a level comparable to commercial EVA.

The material also maintained substantial adhesive strength after repeated cycles of melting and re-bonding. The introduction of the PhLA component improved heat resistance as well.

The team demonstrated biodegradability by treating the polymer with lipase, a fat-digesting enzyme, which caused surface degradation and reductions in both molecular weight and total mass. The research team noted, however, that the rate of decomposition in real natural environments and the feasibility of commercialization require further verification.

The significance of the achievement lies in showing that functional polymers previously dependent on petrochemical processes can now be produced directly using microorganisms. Potential applications span the packaging sector, including temporary fixation of stainless steel components, positioning of metal sheets, removable film adhesion on metal surfaces, kraft paper bonding, corrugated cardboard sealing and paper packaging assembly.

"This research shows that by precisely engineering microbial metabolism, we can go beyond simply producing polymers to directly manufacturing functional materials," Lee said. "Going forward, this could be expanded into a bio-manufacturing technology capable of producing not only petroleum-based adhesive replacements but also a range of functional polymers in a sustainable way."

The findings were published in Nature Communications.


nbgkoo@heraldcorp.com