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Cow’s Gut Microbes: The Key to Breaking Down Plastic

Bacteria found in the rumen of cows show promise to effectively break down plastics and synthetic polymers like PET, PBAT, and PEF, opening a new door for sustainability in reducing plastic litter.

In 2016, about 19 to 23 million metric tonnes, or 11 per cent, of global plastic waste made their way into our oceans, and according to an international study by Borrelle et al., these numbers are expected to skyrocket to 53 million metric tonnes by 2030. Depending on the material and structure, plastics can take around 20 to 500 years to decompose. Given these numbers, it comes as no surprise that plastic waste is one of the greatest environmental threats that require urgent action.

In recent years, the rise of bio-economies has motivated the scientific community to innovate sustainable technologies, with many exploring the hidden prospects of polyester-hydrolysing microbial enzymes found in various ecosystems including but not limited to leaf-branch compost, marine and moss-associated environments.

A group of scientists in Austria was particularly interested in the rumen microbial ecosystem. In their recent study published in Frontiers in Bioengineering and Biotechnology, the researchers dove deep into the rumens of cows and other ruminant animals to explore their heterogeneous microbial community. They discovered that bacteria found in the cow’s rumen can digest certain types of synthetic materials, opening up a new avenue to reduce plastic litter sustainably.

“A huge microbial community lives in the rumen reticulum and is responsible for the digestion of food in the animals,” explained 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.”

Because the diet of most cows already includes natural plant polyesters, the team believed that these bacteria may be able to break down plastics as well. To test their hypothesis, Ribitsch and her colleagues examined how effectively rumen microorganisms can degrade synthetic polyesters, namely polyethylene terephthalate (PET), polybutylene adipate terephthalate (PBAT), and polyethylene furanoate (PEF). PET is one of the most commonly used synthetic polymers in textiles and packaging, while PBAT and PEF are primary biodegradable components of compostable plastic bags.

The team obtained rumen liquid containing the microorganisms from a slaughterhouse in Austria and incubated the liquid with the three polyesters in both powder and film form. Based on their findings, all three types of plastics were broken down by the microbes, with the powdered plastic breaking down quicker than plastic films.

By comparing their result with past studies done on singular microorganisms, the researchers also demonstrated how the rumen liquid with multiple types of bacteria was more effective in breaking down plastics. This observation strongly suggests that the microbial community offers a synergistic advantage, wherein a combination of enzymes is potentially more effective than the action of one specific enzyme.

Although research can be costly due to the pricey lab equipment needed and the extensive pre-studies required to study microorganisms of the rumen, Ribitsch believes that the process is highly scalable considering the large amounts of rumen that accumulate daily in slaughterhouses. With this novel finding, experts hope to shine a light on the underexplored potential of microbial communities as an environment-friendly resource and solution to plastic waste. [APBN]

Source: Quartinello et al. (2021). Together is better: the rumen microbial community as biological toolbox for degradation of synthetic polyesters. Frontiers in Bioengineering and Biotechnology, 9, 500.