I’m sitting here looking at the mounting piles of rubbish in my street because of ongoing strikes, and wondering, “wouldn’t it be great if there was another way to remove the waste?”
Organic waste will eventually decompose, but PET plastics (poly(ethylene terephthalate)) are resistant to bacterial degradation. Hence, the race is on to find bacteria that contain the necessary molecules, known as enzymes, which are able to degrade PET plastic by catalysing chemical reactions.
Recently (March 2016), analysis of PET bottles and “sludge” at a recycling facility were screened for bacterial growth. The researchers sought to find bacteria that preferentially accumulated on the PET surface, and whose colonisation resulted in the degradation of the PET by using it as a nutritional carbon source.
The search proved fruitful and a novel strain of bacteria was identified.
So how has it come to be that there is now a strain of bacteria that can degrade the PET plastics? The researchers speculate that the concentration of PET and the culture conditions promoted the selection of a bacterium that contained the plastic-metabolising enzymes. It appears that these enzymes are the result of mutations that changed the preferential targets of existing enzymes.
However, analyses of ocean plastics also show an accumulation of plastic-eating microbes, while some strains of microbes were identified as early as 1970. And, in 2014 plastic-eating worms were found to have PET-digesting gut microbes, indicating that while an inexhaustible food source has allowed the propagation of these microbe species, the existence of these microbes is not a direct result of the increased presence of plastics.
Further research is now required to investigate how to exploit these microbes, with the aim to end plastic waste build-up on both land and in the oceans. Maybe one day we will all have composting bins for plastics as well as organic waste…..
Yoshida et al, Science (11) MAR 2016 : 1196-1199
Yang et al, Environmental Science & Technology 2014 48 (23), 13776-13784