By Owen Xu Li
A small amount of polymerase can compost biodegradable plastic containers and forks.
Ting Xu and colleagues noted in a Nature report on April 21 that, under moderately warming conditions, the plastic of the enzyme addition film will be affected in standard compost or in tap water in a few days or even weeks.
“Biodegradability is not the same as compostability,” said Xu, a polymer scientist at the University of California, Berkeley and Lawrence Berkeley National Laboratory. She often found some biodegradable plastic in the compost she collected for her parents’ garden. Most biodegradable plastics will enter the landfill and because the conditions are not suitable for them to break down, they will not degrade faster than ordinary plastics.
The inclusion of biodegradable plastic in enzymes will accelerate decomposition. However, this process generally unintentionally forms potentially harmful microplastics, which are emerging in global ecosystems. These enzymes will bind together and randomly cut the plastic molecular chains, resulting in incomplete breakdown. Xu said that “the situation is worse than not demoting them at first.”
Her team added separate enzymes to two types of biodegradable plastics (including polylactic acid, which is commonly used in food packaging). They inserted the enzyme along with a previously developed degradable additive to ensure that the enzyme does not clump or break down. The lone enzymes grabbed the ends of the plastics’ molecular chains and ate, cutting every chain link and preventing microplastic formation.
Adding enzymes makes plastic more expensive and impairs its performance. However, Xu’s enzyme accounts for only 0.02% of the weight of plastic while being just as strong and flexible as that used in shopping bags.
This technology is not suitable for all plastics because their molecular structures are different and Xu’s team is working hard to overcome the limitations. She has filed a patent application for this technology and the co-authors have founded a start-up company to commercialize it. She hopes that in the future, all grocery stores will have that plastic.