A large number of used plastic bottles are discarded every day, but now microorganisms may hold the promise of solving the problem. Now, researchers report in the journal ACS Central Science that they have developed an edible plastic E. coli bacterium that effectively converts polyethylene terephthalate (PET) waste into adipic acid, which is used in the manufacture of nylon materials, medicines and perfumes.
These beads contain modified E. coli bacteria that can effectively convert PET waste into high-value compounds.
Previously, a group of researchers, including Stephen Wallace, engineered a strain of E. coli bacteria to convert terephthalic acid (PTA), the main ingredient in old PET bottles, into something tastier and more valuable: the vanilla-flavored compound vanillin. Meanwhile, other researchers have engineered microbes to metabolize PTA into a variety of small molecules, including short acids. So a new team at Wallace and the University of Edinburgh wanted to expand the biosynthetic pathway in E. coli to include metabolizing PTA into adipic acid, a feedstock for many everyday products that are often produced from fossil fuels through energy-intensive processes.
The team developed a new strain of E. coli that produces an enzyme that converts PTA into compounds such as muconic acid and adipic acid. Then, to convert muconic acid to adipic acid, they used a second hydrogen-producing E. coli and a palladium catalyst. In their experiments, the team found that attaching engineered microbial cells to alginate hydrogel beads improved their efficiency, with up to 79% of PTA being converted to adipic acid. Using PTA samples from discarded bottles and coatings from discarded packaging labels, the engineered E. coli system efficiently produced adipic acid. The researchers say that in the future they will look for ways to biosynthesize other high-value products.
