Turning Gut Bacteria Into Bioplastic Factories

E. coli, a common gut bacteria, can be engineered to produce biodegradable polymers for use in surgical sutures, among other applications.

AsianScientist (Mar. 22, 2016) – A Korean research team has engineered gut bacteria to create non-natural polymers in a biorefinery—allowing various plastics to be made in an environmentally-friendly and sustainable manner. The research was published in Nature Biotechnology.

In recent years, biorefineries which transform non-edible biomass into fuel, heat, power, chemicals and materials have received a great deal of attention as a sustainable alternative to decreasing the reliance on fossil fuels.

Renewable non-food biomass could potentially replace petrochemical raw materials to produce energy sources, useful chemicals, or a vast array of petroleum-based end products such as plastics, lubricants, paints, fertilizers and vitamin capsules.

In the present study, a team headed by Distinguished Professor Lee Sang Yup of the Korea Advanced Institute of Science and Technology (KAIST) adopted a systems metabolic engineering approach to develop a microorganism that can produce various non-natural polymers which have biomedical applications.

According to the researchers, this approach is the first successful example of biological production of poly(lactate-co-glycolate) (PLGA) and several novel copolymers from renewable biomass by one-step direct fermentation of metabolically engineered Escherichia coli (E. coli) bacteria.

The researchers drew inspiration from the biosynthesis process for polyhydroxyalkanoates, biologically-derived polyesters produced in nature by the bacterial fermentation of sugar or lipid. From there, they designed a metabolic pathway for the biosynthesis of PLGA through microbial fermentation directly from carbohydrates in E. coli strains.

PLGA is a biodegradable, biocompatible and non-toxic polymer. PLGA has been widely used in biomedical and therapeutic applications such as surgical sutures, prosthetic devices, drug delivery, and tissue engineering.

In order to produce PLGA by microbial fermentation directly from carbohydrates, the team incorporated external and engineered enzymes as catalysts to co-polymerize PLGA while establishing a few additional metabolic pathways for the biosynthesis to produce a range of different non-natural polymers. This bio-based synthetic process for PLGA and other polymers could substitute for existing complicated chemical production methods.

Lee and his team has also managed to produce a variety of PLGA copolymers with different monomer compositions such as the US Food and Drug Administration-approved monomers 3-hydroxyburate, 4-hydroxyburate, and 6-hydroxyhexanoate. Newly applied bioplastics such as 5-hydroxyvalerate and 2-hydroxyisovalerate were also made.

“We presented important findings that non-natural polymers, such as PLGA which is commonly used for drug delivery or biomedical devices, were produced by a metabolically engineered gut bacterium,” said Lee.

“Our research is meaningful in that it proposes a platform strategy in metabolic engineering, which can be further utilized in the development of numerous non-natural, useful polymers.”

The article can be found at: Choi et al. (2016) One-step Fermentative Production of Poly(lactate-co-glycolate) from Carbohydrates in Escherichia coli.


Source: KAIST; Photo: Shutterstock.
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