“The bacteria can use these compounds as a sole source of carbon, nitrogen, and energy,” said Dr. Hermann J. Heipieper, a senior scientist at the Helmholtz Centre for Environmental Research-UFZ in Leipzig, Germany, and co-author of the new study. “This finding represents an important step in being able to reuse hard-to-recycle PU products.”
Polyurethane Plastics are Used in Almost Everything
Back in 2015, polyurethane products accounted for 3.5 million tons of the plastic generated in Europe. Polyurethane is employed in almost everything, from refrigerators and buildings, to footwear and furniture, as well as in numerous other uses. This product is challenging and energy-intensive to recycle because most of these types of plastics are thermosetting polymers that are not melting when heated.
The debris usually ends up in landfills where it produces several toxic chemicals, most of which are carcinogenic. The use of microorganisms such as bacteria and fungi to decompose oil-based plastics is an ongoing area of analysis at the moment. Still, few studies have focused on the biodegradation of polyurethane, like the new paper.
The team in Germany was able to isolate a bacterium, Pseudomonas sp. TDA1, from a place full of brittle plastic debris that is likely to attack some of the chemical ties that compose polyurethane plastics.
This specific strain is part of a population of bacteria that are renowned for their endurance of toxic organic elements and other types of stress, as per Dr. Christian Eberlein from the Helmholtz Centre for Environmental Research-UFZ. He is a co-author of the study who led and supervised the research.
“That trait is also named solvent-tolerance and is one form of extremophilic microorganisms,” he said.
Converting Oil-Based Plastics Into Degradable Ones
The paper is part of a European Union scientific program called P4SB, which is trying to find advantageous microorganisms that can metabolize oil-based plastics into entirely biodegradable ones. The program has particularly focused on a bacterium called Pseudomonas putida.
Besides polyurethane, the P4SB collaborators are also analyzing the efficacy of microbes to reduce plastics produced from polyurethane terephthalate (PET), which is typically used in plastic water bottles.
Heipieper explained that the first step of any future study on Pseudomonas sp. TDA1 will be made to detect the genes that code the extracellular enzymes that are able to decompose specific chemical elements in polyester-based polyurethanes. Extracellular enzymes, also known as exoenzymes, are proteins produced outside of a cell that triggers a biochemical reaction.
Still, there is no immediate plan to manage these or other enzymes utilizing artificial biology methods for bioplastic manufacturing. That could comprise, for example, genetically changing the bacteria into mini-factories able to convert oil-based chemical elements into biodegradable ones for eco-friendly plastics.
The team of researchers said that more ‘fundamental knowledge’ like the one collected in the current paper is a must before experts can make that technological and commercial hop.