Of the (estimated) 300 million tonnes of plastic produced worldwide every year, only around 20% is currently recycled or incinerated. Much of the remaining 80% eventually ends up in the environment.
In the environment, plastics are degraded by weathering, UV light, abrasion, and mechanical action etc - but they are also degraded by microbes (e.g. Proteobacteria, Actinobacteria, Bacteroidetes, and Firmicutes) and by fungi.
Biodegradation of plastics has now been observed in polythene [PE], polypropylene [PP] , polystyrene [PS] , PVC and polyamides [PA] (e.g Nylon). The specific enzymes produced by the organisms, and which are responsible for the degradation, are for the most part unknown.
Although an increasing number of microorganisms have been isolated and identified recently, the responsible enzymes or associated degradation pathways are rarely identiﬁed for many types of synthetic polymers.
Source : Materials, 14, 3
Note : Although many research groups are currently investigating the possible uses of micro-organisms to potentially remove plastics and microplastics from the environment, the possible harmful effects of the degradation products are also largely unknown.
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