The Plastic problem

According to a 2017 American Association of Science report, humans generated 9.1 billion tons of plastic since the 1950s. Only 9 percent of that plastic was successfully recycled, and much of the rest gets dumped in landfills, where it lingers for decades and even centuries. 

Even worse, it can get broken down into smaller microplastic and ends up in the ocean, where it chokes marine life.

“The main issue is not technical. It is economic,” Farnaud says. “There is no money in recycling plastic, so that investment to develop these technologies [is] very difficult to find.”

A cow farting in a feedlot isn’t just a roadside view in the midwest: for climate scientists, it’s a cause of concern. After all, cow farts and belches release significant amounts of methane into the atmosphere. Beef production currently accounts forEmissions from livestock account for about 14.5 percent of total greenhouse gas emissions, globally, and roughly two thirds of those emissions come from cattle — 3.7 percent of greenhouse gas emissions in the U.S. ...microbes that break down food in the cow gut could help solve the massive plastics problem engulfing planet Earth.

What’s new — Cow guts, the rumen, bacteria digest plant cellulose from the grass and feed that the cow eats. 

The researchers speculate that because the cow’s gut breaks down natural plant polyesters, the rumen flora could probably do the same for polyesters found in plastic materials. 

The team thus tested how well cow rumen could degrade or break down three common polyester materials found in plastic: 

• Polyethylene terephthalate (PET) — A lightweight plastic that is found in many common types of packaging, including water bottles

• Polybutylene adipate-co-terephthalate (PBAT) — A biodegradable plastic that has been used in compostable packaging

• Polyethylene furanoate (PEF) — A plastic made of renewable materials that serves as an alternative to PET for bottle drinks and packaging. (5)

Although multiple bacteria inhabit the cow’s rumen, this lesson focuses on two harmless microbes, Ruminococcus and Selenomonas, which break down cellulose and starch in plant matter, respectively. These bacteria obtain nutrients from the cow’s diet, and the cow gains energy from the products of bacterial metabolism (1)

These bacteria are the most actively cellulolytic of all mesophilic organisms described to date from any habitat. In light of numerous proposals to improve microbial cellulose digestion in ruminants, it is instructive to examine the characteristics of these species that contribute to their superior cellulolytic capabilities and to identify the factors that prevent them from digesting cellulose even more rapidly. As a group, these species have extreme nutritional specialization. They are able to utilize cellulose (or in some cases xylan) and its hydrolytic products as their nearly sole energy sources for growth. Moreover, each species apparently has evolved to similar maximum rates of cellulose digestion (first-order rate constants of 0.05 to 0.08 h-1). (2)

Genetically modified bacteria break down plastics

By introducing the plasmid containing the I. sakaiensis genes into V. natriegens bacteria, the researchers were able to get V. natriegens to produce the desired enzymes on the surfaces of their cells. The researchers then demonstrated that V. natriegens could break down PET in a saltwater environment at room temperature. (3)

Turning Plastic Into Food

The first step in Techtmann's process is to put the plastic through a reactor to break up the plastic's tough infrastructure and start breaking down those long polymer chains. This process turns the plastic into an oily substance, with carbon, oxygen, and hydrogen unlocked from the plastic's molecular structure. That oily substance is then fed to hungry bacteria that thrive on those three elements and prefer them in that form. "We're taking bacteria that are really good with oily compounds and feeding them that pre-chewed-up plastic," says Techtmann. Bacteria grow quickly on this diet and make more bacteria cells, which are about 55 percent protein. Those cells are then dried out, and that's what becomes the protein powder.(4)

Plastics to Ice Cream

. Bacterial species from Pseudomonas, Escherichia, and Bacillus genera exhibit enormous potential for degrading plastics, especially for recalcitrant polymers, such as PE, PET, PS. Additionally, it has been demonstrated that bacterial strains, such as Pseudomonas aeruginosa, Bacillus megaterium, Rhodococcus ruber, and others may break down the thermoplastics PE and PET [5]. Furthermore, fungi able to degrade plastics have a powerful enzymatic system. Filamentous fungi play an important role in the degradation and mineralization of plastic pollutants. They have the ability to degrade PE and PET [33]. With more research, it was discovered that microorganisms able to degrade plastic vary in the diversity, abundance, and activity, providing plastic-degrading evidence. (source)