This finding significantly affects the possibility of recycling. More than 82 million tons of PET are produced worldwide each year, and only a small fraction is recycled to make new plastic. And the process of sending plastic products to recycling plants to melt them down and make something new is energy-intensive and expensive. On the other hand, biorecycling can help create a cheap and efficient circular economy for plastics.
For the past few years, scientists have been racing to develop plastic-eating bacteria for just that purpose. PHL7 stands out from other candidates identified so far. The way it quickly breaks down PET seems to depend on a single building block on photo retouching its DNA. At a specific point in its amino acid sequence, PHL7 carries a leucine, while the other enzymes carry a phenylalanine residue. In the past, leucine at this position has been associated with polymer binding to enzymes.
When German researchers replaced phenylalanine with leucine on another enzyme, the organism became faster at breaking down plastic. In fact, its efficiency rivals that of PHL7. In the lab, the PHL7 enzyme was also able to bind to more polymers than the LLC enzyme. "These results suggest that the substitution of leucine by phenylalanine for leucine may be part of the reason for the variation in binding energy of each residue in PHL7," the study authors wrote.