Biofilms are populations of bacteria that tend to group and stick to surfaces with the help of a self-produced extracellular matrix of biopolymer. Biofilm grows everywhere, from our teeth to bathroom to lakes, in almost any environment with a combination of moisture, nutrients, and a surface.
Liu and the team led by James Kar-Hei Fang and Professor Song Lin Chua at Hong Kong Polytechnic University have taken advantage of this sticky exopolymeric substance produced by biofilms to create microbial nets that can immobilize microplastics. They have engineered the bacterial Pseudomonas aeruginosa biofilm found in all ecosystems to colonize microplastics. In a bioreactor, the biofilm captures microplastics floating in the water, aggregating them, and making them heavy, so they eventually sink to the bottom. Then, using a biofilm-dispersal gene, a “capture-release mechanism” is developed that allows the researchers to release the microplastics from the biofilm, which can be later recovered for recycling.
Researchers have demonstrated the potential application of this biofilm technology in controlling microplastics pollution in seawater samples collected near a sewage outfall. However, the experiment is still at the preliminary stage, carried out as a proof-of-concept test in a controlled lab environment and not in the ocean or sewers. Also, Pseudomonas aeruginosa is a pathogenic bacterium and probably cannot be used in large-scale projects. Nevertheless, the researchers are confident that the method can be replicated in wastewater plants or other watery environments using natural biofilm-forming bacteria. This process is an innovative and exciting application of biofilm engineering to address the plastic pollution crisis.