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Microbes in cow stomachs can break down plastic
- burlesona 5y agoCan anyone with a better understanding of the chemistry help me understand the level of plastic “degradation” this represents? My (low) understanding is that we know of several processes that partially break plastic down, but nothing that actually metabolizes it or turns it into useful / non-toxic material. Is this a breakthrough, or just another example of partial breakdown without truly consuming the plastic?
- thatcat 5y agoPlastic is a polymer, like cellulose. It's well known that microbes have evolved some enzymes to breakdown biopolymers - cellulase, which is present in rumen fluid. It is also known that pseudomonas has enzymes that are capable of breaking down hydrocarbon chains in oil - since that is the precursor for plastic polymers it should be no surprise that there are pseudomonas strains capable of breaking down plastic polymers. This paper claims that there is such a strain that is dominant in this rumen fluid that does so through a hydrolysis reaction (likely using an enzyme produced in that strain as a catalyst). Hydrolysis cleaves terephthalic acid in this process - a monomer that contains an aromatic ring. So essentially the final size of the polymers depends on the placement of that unit in that particular polymer. You need several enzymes working in sequence to degrade a complex polymer fully, but it is possible. https://en.wikipedia.org/wiki/Terephthalic_acid https://en.wikipedia.org/wiki/Terephthalic_acid
- longcommonname 5y agoOp question made me think of a few others. Why is a molecules with high energy density so difficult to break down? Why are there so few natural decomposers of plastics? Is this because bacteria haven't evolved the correct enzymes, and many other non plastics globally have bacteria consumers that we can just assume that they decompose naturally?
- thaumasiotes 5y ago> Why are there so few natural decomposers of plastics? Because plastics weren't naturally occurring. Give it time.
- idiotsecant 5y agoMaybe a lot of time. The main reason we have cheap coal is from nature failing to find a solution to break down lignin during the Carboniferous period (and really particularly during the Carboniferous rainforest collapse) hundreds of millions of years ago. Sometimes nature is very slow. Like geological timescales.
- thatcat 5y agoLignin can be broken down in aerobic conditions by peroxidase and a series of other fungal enzymes, it only forms those energy dense forms under anaerobic conditions and probably requires high pressures. The reason it is so difficult and only breaks down through oxidation is because it is quite complex, unlike the homogenous polymer chains of plastic that have many repeating monomers. https://www.researchgate.net/figure/Chemical-structure-of-lignin-source-lignoworks_fig1_315348668 https://www.researchgate.net/figure/Chemical-structure-of-li...
- ABCLAW 5y ago>Why is a molecules with high energy density so difficult to break down? Generally, even if a given reaction is energetically favourable, if the activation energy or enabling conditions for the reaction to occur are high/rare respectively, then the rate of the energetically favourable reaction will be slow. It's like water in a cup; sure it would prefer to be on the ground, but absent something tipping the cup over, it'll stay inside the current local energy minima without any complaints.
- stkdump 5y agoOn the other hand (having no idea about the subject) I can imagine that the fact that plastics can't be broken down so easily is part of the reason why we find it so useful, for example to protect foods.
- morpheos137 5y agoThere are many forms of plastic made from many different chemicals. Fortunately some of the most common ones like polyethylene are chemically harmless to life. Some plastics like PVC and some synthetic rubbers may contain hazardous additives but most plastics are quite harmless.
- danwills 5y agoIt seems to me that with humans making so much of these 'harmless' (or at least relatively-low-toxicity) plastics, we have essentially created a giant niche waiting there for the first micro (or even perhaps macro) organism(s) that can live off this stuff, they are srsly going to have a massive field day once their day roles around! It could of course be fairly troubling when pieces of our various machines/buildings/etc start to decompose earlier than expected! This assumes quite some luck in terms of mutation to be fair, and maybe humans might also help with speeding that up too? could be good!?
- morpheos137 5y agoWhy don't people worry about sand? Nothing eats it. It can mechanically irritate animals (see pearls). How is polyethylene different? The reddit driven hysteria about plastics in general is vastly out of purportion to the actual harm done by plastics.
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- hanniabu 5y agoI can see it now, Big Meat will start feeding cows plastic because it's cheaper
- LegitShady 5y agomalk, now with vitamin BPA!
- Apocryphon 5y agoPutting the xenoestrogens in estrogen.
- hn_go_brrrrr 5y agoNot just cheaper, but also better for the environment. /s
- nkssy 5y agoGiven you can (sort of?) make plastic from milk I'm not surprised.
- BugWatch 5y agoThis reminds me of that tale/urban legend/reality when, once upon a time, some cows were eating the old Trabant cars (that had an outer body made od some type of plastic).
- Ygg2 5y agoPretty sure that was pigs. I remember seeing that scene in some Serbian movie. Edit: It's a scene from Black cat, white cat by Emir Kusturica.
- markvdb 5y agoThe Trabant bodywork was made of Duroplast[0], a thermosetting resin plastic reinforced with cotton waste from the Soviet Union. [0] https://en.wikipedia.org/wiki/Duroplast https://en.wikipedia.org/wiki/Duroplast
- johnnyApplePRNG 5y agoWould it not be more likely to find microbes that can break down plastic on plastic itself? (Why are we looking in cow's stomachs for "eco-sustainable plastic degradation and recycling processes" I guess is my question?)
- toast0 5y agoCow stomachs are a good place to find digestive microbes. Nice temperature, humidity, ph and what not.
- azeirah 5y agoWe did! The other well known bacteria that can break down plastic were found in a plastic waste facility in Japan. I think it's pretty clearly just a case of more is better
- reedjosh 5y agoCows are amazing!
- mandliya 5y agoI remember news stories in India of cows dying because of ingesting too much plastic. https://wewantrefill.com/cows-india-die-consuming-plastic-waste/ https://wewantrefill.com/cows-india-die-consuming-plastic-wa...
- Proven 5y agoHoly cow! I'll leave it to AOC and American progressives to get the government to engineer those for humans and give every ICE car or truck owner a quota - say 20kg per year!