Bacteria found in cow stomachs can be used to digest polyesters used in
textiles, packaging, and compostable bags, according to a new study by the
open access publisher Frontiers. Plastic is notoriously hard to break down,
but microbial communities living inside the digestive system of animals are
a promising but under-investigated source of novel enzymes that could do the
trick. The new findings present a sustainable option for reducing plastic
waste and litter, co-opting the great metabolic diversity of microbes.
Plastic is notoriously hard to break down, but researchers in Austria have
found that bacteria from a cow’s rumen – one of the four compartments of its
stomach – can digest certain types of the ubiquitous material, representing
a sustainable way to reduce plastic litter. The discovery is published today
in the open access journal Frontiers in Bioengineering and Biotechnology.
The scientists suspected such bacteria might be useful since cow diets
already contain natural plant polyesters. “A huge microbial community lives
in the rumen reticulum and is responsible for the digestion of food in the
animals,” said Dr Doris Ribitsch, of the University of Natural Resources and
Life Sciences in Vienna, “so we suspected that some biological activities
could also be used for polyester hydrolysis,” a type of chemical reaction
that results in decomposition. In other words, these microorganisms can
already break down similar materials, so the study authors thought they
might be able to break down plastics as well.
Ribitsch and her colleagues looked at three kinds of polyesters. One,
polyethylene terephthalate, commonly known as PET, is a synthetic polymer
commonly used in textiles and packaging. The other two consisted of a
biodegradable plastic often used in compostable plastic bags (polybutylene
adipate terephthalate, PBAT), and a biobased material (Polyethylene
furanoate, PEF) made from renewable resources.
They obtained rumen liquid from a slaughterhouse in Austria to get the
microorganisms they were testing. They then incubated that liquid with the
three types of plastics they were testing (which were tested in both powder
and film form) in order to understand how effectively the plastic would
break down.
According to their results, all three plastics could be broken down by the
microorganisms from cow stomachs, with the plastic powders breaking down
quicker than plastic film. Compared to similar research that has been done
on investigating single microorganisms, Ribitsch and her colleagues found
that the rumen liquid was more effective, which might indicate that its
microbial community could have a synergistic advantage – that the
combination of enzymes, rather than any one particular enzyme, is what makes
the difference.
While their work has only been done at a lab scale, Ribitsch said, “Due to
the large amount of rumen that accumulates every day in slaughterhouses,
upscaling would be easy to imagine.” However, she cautions that such
research can be cost-prohibitive, as the lab equipment is expensive, and
such studies require pre-studies to examine microorganisms.
Nevertheless, Ribitsch is looking forward to further research on the topic,
saying that microbial communities have been underexplored as a potential
eco-friendly resource.
Reference:
Quartinello F, Kremser K, Schoen H, et al. Together Is Better: The Rumen
Microbial Community as Biological Toolbox for Degradation of Synthetic
Polyesters. Front Bioeng Biotechnol. 2021;9. doi:
10.3389/fbioe.2021.684459