May Cows Solve the Plastics Problem?
Scientists striving to solve the problem of plastic pollution keep working relentlessly. They have now discovered that some microorganisms in a cow’s stomach, especially one of its compartments called the rumen, are able to break down various plastic materials.
The diet of ruminants already contains certain natural polyesters. Cutin, the waxy substance in apple or tomato peels is one example. To break down this substance, bacteria or fungi secrete an enzyme called cutinase, which triggers a series of chemical reactions resulting in water molecules degrading cutin.
Since these amazing friends are able to degrade natural polyesters, Austrian scientists wondered about the possibility of using a similar way to degrade synthetic polyesters, with chemical structures not too different than their natural counterparts. Dr Doris Ribitsch from the University of Natural Resources and Life Sciences in Vienna focused on three plastics: PET (polyethylene terephthalate) used in food packaging and water bottles, PBAT (polybutylene adipate terephthalate) used in biodegradable bags, and PEF (polyethylene furanoate) produced from plant materials.
In the experiments, these three plastic materials were placed in the rumen liquid, in both powder and film form. The results showed that all of them could be broken down by the rumen juice of cows, and only in a couple of hours. The researchers also saw that plastics in powder form dissolved a little faster and PEF was the fastest to break down.
The interesting part is that the results were more successful than those in similar experiments previously conducted by isolating a single species of microorganisms. This means the enzymes produced by the microbial community in the rumen fluid cumulatively provide a synergistic advantage, strengthening the effect of individual enzymes. The overall effectiveness is reported to be higher than any similar experiment conducted in the past 10 years.
Although the experiments in the laboratory yielded successful results, it is still early for real life implementations. The next step is to identify the microorganisms that can break down plastics and the enzymes secreted by these microorganisms. (According to the analysis of DNA samples, 98% of the microbiota in the rumen consist of bacteria, with Pseudomonas species being the most dominant.) Only then it will be possible to reproduce these microorganisms and establish large-scale recycling systems based on them. However, we should not forget that thousands of microorganisms live in the stomachs of cows. Besides, microorganisms that can effectively break down harder plastics such as polyethylene and polypropylene are yet to be discovered. With these said, scientists have a long road ahead.
Regardless, it will certainly be bliss for the whole world if we manage to pave the way for degrading plastics through biological processes on an industrial scale.
- 1. https://www.livescience.com/cow-stomach-bacteria-break-down-plastic.html
- 2. https://phys.org/news/2021-07-microbes-cow-stomachs-plastic.html
- 3. https://edition.cnn.com/2021/07/02/world/cows-plastic-scli-intl-scn/index.html
- 4. https://www.theguardian.com/environment/2021/jul/02/study-suggests-bacteria-in-cows-stomach-can-break-down-plastic