Mussels have the uncanny power to stick to almost anything. Whether it’s a rough metal surface or a wet slippery rock, their grip is unmatched. Inspired by this natural adhesive, researchers at Rice University have taken a bold step toward tackling one of the world’s largest environmental challenges—plastic pollution.
These scientists have bioengineered a version of Escherichia coli (E. coli) bacteria that can break down polyethylene terephthalate (PET), the material commonly used in plastic bottles. By tapping into the sticky power of mussels, they’ve made the bacteria not only cling to plastic but also devour it.
Mussels Meet Bacteria
PET accounts for over 40 percent of the single-use plastic bottle waste in the US and makes up 12 percent of the world’s total solid waste. In fact, once dumped in a landfill, PET-based plastic products don’t decompose for up to 450 years.
“Very excitingly, our research holds promise for addressing the growing problem of plastic pollution in the U.S. and across the globe,” Han Xiao, one of the researchers and a professor of chemistry at Rice University, said.
The new mussel-inspired bacteria not only has the potential to solve this problem, but it can also help clean up biofouling — the unwanted accumulation of plants, microorganisms, animals, and algae, that often damage vessels and block underwater pipelines and water supply systems.
The sticky nature of mussels is due to special adhesive proteins made of an amino acid called DOPA (3,4-dihydroxyphenylalanine).
“DOPA serves as a post-translational modification amino acid present in mussel foot proteins. Mussels exploit the exceptional adhesive properties of DOPA to adhere to a wide range of surfaces,” the study authors note.
Xiao and his team introduced DOPA to the genetic material of E. coli, as well as a group of enzymes referred to as PET hydrolases (PETase). They did this using genetic code expansion, a technique that enables scientists to add new material to existing genetic code, creating new types of amino acids and proteins.
While DOPA gave bacteria the power to grab plastics and adhere to the plastic surface, PET hydrolases allowed them to break down PET into tiny molecules.
“Plastics are big polymers built up by repeated small molecule units. PETase is an enzyme that can hydrolysis these polymers, which work as sharp scissors to break plastic into its small molecule building blocks,” Mengxi Zhang, lead study author and a graduate student from Rice University told ZME Science.
These modifications turned the bacteria into a plastic eater with exceptional adhesive power.
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“Bacteria armed with DOPA-containing surface protein show 400x more adhesive power than bacteria with normal surface protein,” Zhang said.
“This innovative approach could provide a novel solution to plastic recycling, offering a faster and more efficient way to reduce plastic waste and its environmental impact,” the study authors added.
Broad Potential Beyond Plastics
The researchers tested the modified E. coli bacteria’s ability to degrade PET samples at 98.6 °F (37°C). They claim the experiment was successful as the engineered microorganism degraded a decent amount of plastic.
“Although we didn’t calculate the absolute amount of plastic degradation, we did a comparison. So compared to bacteria with only PETase, our engineered bacteria with the assistance of DOPA showed an enhanced efficiency (2.45-fold increase),” Zhang said.
Bioengineered bacteria aren’t limited to solving our biofouling and plastic problems. The DOPA-modified proteins can also be used to prevent unwanted microbial growth on medical equipment and other surfaces.
This could make bio-implants, drug delivery robots, surgical devices, and various other applications safer than ever. Hopefully, further research will bring us closer to realizing these solutions on a large scale.
The study is published in the journal Small Methods.