Biodegradable plastic from E.coli

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In recent years, polylactic acid (PLA) has attracted attention as a replacement for petroleum-based plastics. It is made from corn-starch, or other starch-rich substances like maize, sugar or wheat, and is biodegradable – reverting in less than 60 days in ideal conditions. PLA is already used as a material for compost bags, food packaging, and disposable tableware, and also for a number of biomedical applications, such as sutures, stents, dialysis media and drug delivery devices. Although its price has been falling, PLA is still more expensive than most petroleum-derived commodity plastics, but now a team of researchers has succeeded in simplifying the production of PLA and making the process much cheaper, meaning we could soon see PLA used in a much wider variety of applications.

Until now PLA has been produced in a two-step fermentation and chemical process of polymerization, which is complex and expensive. Now, through the use of a metabolically-engineered strain of E.coli, the team from South Korea’s KAIST University and the chemical company LG Chem, have developed a one-stage process which produces polylactic acid and its copolymers through direct fermentation. This makes the renewable production of PLA and lactate-containing copolymers cheaper and more commercially viable.

"By developing a strategy which combines metabolic engineering and enzyme engineering, we've developed an efficient bio-based one-step production process for PLA and its copolymers," said the research team’s leader, Prof Sang Yup Lee. "This means that a developed E.coli strain is now capable of efficiently producing unnatural polymers, through a one-step fermentation process."

This combined approach of systems-level metabolic engineering and enzyme engineering now allows for the production of polymer and polyester-based products through direct microbial fermentation of renewable resources.