How Does Bacteria 'Eat' Plastic Pollution?

Scientists in Germany have struck upon a species of bacteria which could aid in the battle against plastic pollution by “eating” a common type of polymer. The research, which was published in the journal Frontiers in Microbiology last month, found that the bacterium Pseudomonas putida feeds on polyurethane diol, which is often applied to substances to prevent them from corrosion.

Polyurethane is difficult to dispose of for two reasons. On one hand, it’s highly flammable, meaning it must be treated with flame retardants that could potentially have carcinogenic properties, so its disposal must be carefully managed. On the other, it’s not a favoured food source of microbes, so it generally persists in the atmosphere for decades, accumulating in both the environment and in food chains. However, the new research may open up a potential avenue of tackling this tricky problem.

The persistence of polyurethane

Polyurethane is one of the most common polymers used in the manufacture of all sorts of goods, from shoes and spandex clothing to mattresses and building materials. As a large polymer composed of many different monomers, polyurethane takes a significant amount of time to break down, which is why it’s so often seen in landfills all over the world.

Even more concerning, it’s one of the more dangerous forms of microplastics, given that it can act as a carrier of other contaminants, which can infiltrate our soil, water and food chain. “Big plastics cannot enter into or be absorbed into tiny microorganisms, so bacteria typically do not degrade polyurethane, even if they are capable of metabolizing little bits and pieces of it,” explained Professor Rolf Halden, who was not involved in the German research but has spent many years studying polymers such as polyurethane.

A small step towards a potentially huge solution

As part of their investigation, the team of scientists from universities and research centres in Braunschweig, Freiberg and Leipzig isolated a strain of a bacterium which seemed to be subsisting solely on plastic waste. After identifying the bacterium as Pseudomonas putida, they tested out its ability to thrive from a solid diet of polymers in the laboratory and found that incredibly, the bacteria were able to derive carbon, energy and nitrogen from the compound, making it entirely sustainable.

But while Pseudomonas putida is capable of metabolising the base components of polyurethane into the sustenance it needs to survive, it’s unlikely to be able to degrade sizable polymers on its own. As such, there is still a long way to go before the bacteria can be called upon as a viable means of combatting plastic pollution, but it’s an important first step. Meanwhile, the scientific community continues to pursue ever more innovative ways of tackling the problem, including through the unlikely union of artificial intelligence and forensic science that can automatically categorise objects through machine learning, then dispose of them accordingly.