The new technique uses a sticky bacterial biofilm to trap microplastic particles, which can then be processed and recycled.
A team led by Yang Liu of Hong Kong Polytechnic University tested the bacterium Pseudomonas aeruginosa to capture microplastics in a bioreactor. This particular species of bacteria is known to colonize microplastics in the environment.
Bacterial biofilms made with P. aeruginosa cause microplastics to aggregate together, and eventually sink. Liu said that in bioreactors, this makes the microplastics more convenient to collect.
Once the microplastics sank to the bottom of the reactor, the researchers used a biofilm-dispersal gene to release them. According to Liu, this allows convenient release of microplastics from the biofilm matrix, which is otherwise difficult and expensive to degrade, so that the microplastics can be later recovered for recycling.
Microplastics can enter the environment through a number of sources including the breakdown of larger plastic pieces, posing a major risk to food chains and human health. The current methods for microplastic disposal, such as landfill storage, are limited and have many disadvantages.
“They are not easily biodegradable, where they retain in the ecosystems for prolonged durations. This results in the uptake of microplastics by organisms, leading to transfer and retention of microplastics down the food chain,” explained Liu.
“Due to their huge surface area and adsorption capacity, microplastics can adsorb toxic pollutants, such as pesticides, heavy metals, and drug residues at high concentrations. This leads to biological and chemical toxicity to organisms in the ecosystems and humans after prolonged unintended consumption of such microplastics.”
“Moreover, microplastics are also difficult to remove in wastewater plants, resulting in their undesired release into the environment.”
Going forward, the researchers plan to isolate and identify natural pro-biofilm forming bacterial isolates either from the sewage or from marine environments.
The experts hope the technique will eventually be used in wastewater treatment plants to help prevent microplastics from escaping into the ocean.
The research was presented at the Microbiology Society Annual Conference Online 2021.