by Gowri Sunil
Opinion Editor

Since the late 1960s, the proliferation of plastic in consumer goods has resulted in severe plastic pollution. Plastic’s lengthy degradation time has only aggravated its strain on ecosystems. To combat this, biodegradable plastics have become a promising substitute; however, their efficacy in decomposing in nature remains uncertain. Recently, microbiologist Harry Lerner and Professor David Schleheck, along with their research team from the University of Konstanz in Germany, discovered a new bifunctional enzyme that can help both break down biodegradable plastics and exhibit antibiotic resistance.

At the beginning of their investigations, the researchers studied how bacteria in forest soil respond to long-chain aliphatic polyester (LCAP), an experimental biodegradable plastic. The team observed LCAPs after burying them four inches beneath the university’s botanical garden’s soil. After a year, the team inspected the LCAPs under a microscope and found they were covered in tiny holes, similar to the shape of bacteria cells. Moreover, microorganisms fully decomposed the bioplastics within an approximate timeframe of 250 to 330 days, while polyethylene, a non-biodegradable plastic, remained mostly unchanged. This difference is significant because LCAPs can be naturally broken down by microorganisms, making them a promising substitute for traditional plastics like polyethylene, which can stay in the environment for years.

Upon further examination, the researchers discovered a new enzyme called LCPH1 that they hypothesized were responsible for the holes in the LCAP. Enzymes are proteins that serve as catalysts for chemical reactions. The LCPH1 enzyme allows bacteria to break apart the polyester’s long molecular chains into smaller parts that the organisms can use for nutrients and energy. Due to its unusual shape, the LCPH1 enzyme has been nicknamed the Pac-Man enzyme. Its wide opening can take in long molecules and break them apart into smaller pieces, similar to the famous arcade character that chomps at pellets in its maze. 

On top of this, researchers found that the Pac-Man enzyme also breaks down beta-lactam antibiotics, a medicine family that includes penicillin. Some bacteria can resist these drugs by producing enzymes that deactivate the antibiotics before they take effect. With both these abilities present in the Pac-Man enzyme, researchers unexpectedly found a link between breaking down bioplastics and antibiotic resistance. 

As of now, the Pac-Man enzyme has created an opportunity to understand how bacteria is adapting to relatively new synthetic materials. Schleheck commented, “This is encouraging, because it seems that bacteria can adapt to breaking down polyester plastics more quickly than we expected.” The new enzyme cannot break down just anything, though, which is evident from the negligible degradation of polyethylene. Instead of remediating existing plastic pollution, the enzyme may help researchers design future plastics with a chemical composition that microorganisms will be able to break down.

(Sources: PHYS org, SCI News, The Microbiologist)