Simpler, cheaper, biodegradable plastic without using fossil fuels

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.

"The polyesters and other polymers we use everyday are mostly derived from fossil oils made through the refinery or chemical process," said Lee. "The idea of producing polymers from renewable biomass has attracted much attention due to the increasing concerns of environmental problems and the limited nature of fossil resources. PLA is considered a good alternative to petroleum-based plastics as it is both biodegradable and has a low toxicity to humans."

The team's research is published in two papers in the journal Biotechnology and Bioengineering.