Bacteria, such as E. coli (pictured), produce polymers to store nutrients.Credit: Steve Gschmeissner/Science Photo Library
Researchers have genetically engineered microbes to produce a strong, flexible plastic similar to nylon for the first time.
Bacteria have been used to generate polyesters such as polyhydroxyalkanoates (PHAs) in the past but, nylon-like plastics such as those used in clothing and shoe manufacturing have been difficult to create, the authors report in Nature Chemical Biology today1.
“The work is beautiful,” says Colin Scott, the head of enzyme engineering at Uluu, a company based in Perth, Australia, that uses microbes to produce compostible PHAs from seaweed.
Around 400 million tonnes of non-degradable, petroleum-based plastic waste and microplastics are produced each year globally, endangering wildlife, human health and the planet. “This work really highlights how much biology can do to help address this crisis,” says Scott.
Hacking nature
Bacteria naturally produce polymers to store nutrients in times of scarcity, but using bacteria to create a nylon-like plastic is challenging because there are no naturally occurring enzymes that create this type of polymer, says co-author Sang Yup Lee, a biomolecular engineer at the Korea Advanced Institute of Science and Technology in Daejeon, South Korea.
To solve this problem, the researchers modified enzyme-coding genes from a range of bacterial species and inserted them as loops of DNA called plasmids into Escherichia coli, a bacterium often used for proof-of-concept work.
These genes then encoded several new-to-nature enzymes that could link up chains of molecules to create polymers. The end product was a bioplastic called poly(ester amide), or PEA, that consisted mainly of polyester with a few nylon-like amide bonds.
Nylon is a 100% amide-bond containing polymer, so there is still some way to go before bacteria can properly mimic this type of plastic, says Yup Lee.
Testing revealed that one type of PEA had physical, thermal and mechanical properties comparable to those of polyethylene, one of the most widely used commercial plastics.
But Seiichi Taguchi, a bioproduction engineer at Kobe University in Japan, says it is unlikely the plastic would be as strong as polyethylene because of the low frequency at which the amino acids were incorporated into the polymers. And adding an amino acid to a polymer often leads to the termination of the chain, creating stunted polymers with low molecular weights, he says.
