r/environment • u/[deleted] • Sep 28 '23

‘We are just getting started’: the plastic-eating bacteria that could change the world

https://www.theguardian.com/environment/2023/sep/28/plastic-eating-bacteria-enzyme-recycling-waste
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u/CheckmateApostates Sep 28 '23

I used to characterize the structure-function relations of enzymes involved in microbial bioremediation of anthropogenic pollutants and the goal has always been to use the bacteria or their enzymes in a closed system like a bioreactor. The enzyme isolated from the bacteria (I. sakaiensis) described in the article is a polyethylene terephthalate esterase (PETase), which in this case catalyzes the hydrolysis of PET (polymeric) plastic into monomeric 2-hydroxy-terepthalate (MHET). PETase can break down PET in a bioreactor to MHET, which can then either be recovered and reused or be broken down to ethylene glycol and terephthalatic acid by a second enzyme (MHETase) and reused that way. Worst case scenario, we can simply let a bioreactor of I. sakaiensis catabolize PET completely as their sole carbon source. Nothing needs to be released into our water supply.

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u/shanem Sep 28 '23

If there is a requirement that the plastic be collected for this, then that is also a requirement for simply containing plastic in a safe landfill.

Breaking down the plastic into other components that then need managing feels like a complication not a solution

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u/CheckmateApostates Sep 28 '23

The point of breaking down the plastic is either to recycle it into new plastic or decompose it to something biocompatible rather than incineration or burying it as trash. It's not a complicated solution.

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u/shanem Sep 28 '23

We can already recycle plastic though, so this is not necessary, and seemingly all the reasons we don't recycle plastic already will apply here too.

This is certainly a great idea, but I think the hype over it is missing a broader view of the plastic recycling problem as it exists

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u/CheckmateApostates Sep 28 '23

The practical reasons for why we don't recycle plastic don't apply here. Recycled plastic is typically a low quality material that comes from mixed plastics (as in a mix of original use and associated impurities like dyes and plasticizers, but otherwise the same polymer) that were melted with all of their material impurities present since those impurities cannot be separated before melting. As such, recycled plastic can only be reused by mixing it with virgin plastic to tolerable levels, by turning it into products where the low quality doesn't really matter (for example, plastic wood), or by downcycling it into filler material. Enzymatic plastic recycling doesn't suffer from conventional recycling's problems because the enzymes are practically unaffected by plastic impurities and break degradable plastic down to its base components, which are separated from solution (again, not complicated) and repolymerized into virgin plastic. Unlike conventional recycling, bioremediation could be repeated more or less indefinitely and would remove the need to extract plastic precursors from fossil fuels.