Engineering cells to pump out fluoropolymers

Chemists have worked extensively to develop synthetic methods to incorporate fluorine into all types of molecules and materials. But one strategy they haven’t explored much is commandeering the machinery in living cells to biosynthetically produce fluorinated compounds. The challenge is that cells lack the ability to make many fluorinated organic compounds or to metabolize them. A team led by Michelle C. Y. Chang of the University of California, Berkeley, in trying to overcome that limitation, has engineered Escherichia coli host cells to convert a stable, nontoxic compound called fluoromalonate into 2-fluoro-3-hydroxybutyrate, a fluorinated diketide (Angew. Chem. Int. Ed. 2017 DOI: 10.1002/anie.201706696). Chang’s group previously focused on using fluoroacetate as a starting material, but it’s a compound that can poison cells when it’s metabolized. Now, using malonate transporters to introduce fluoromalonate into the cells, the chemists were able to improve the fluorinated compound’s uptake from micromolar to millimolar levels. They also demonstrated that a polymerase enzyme in the engineered cells can act on the fluor­inated diketide monomer to produce the corresponding fluorinated poly(hydroxyalkanoate). Poly(hydroxyalkanoates) are found in products like biodegradable forks and spoons. Chang notes that using biosynthesis for commercial bioplastic production isn’t yet cost-effective, but this strategy could allow chemists to control polymer chain length and other properties in designer applications.