Why are microorganisms unable to break down plastics?
1 Answer
They haven't evolved to do so. Plastics as a class of compounds are simply too new!
Explanation:
Basically, because microorganisms have evolved over millions of years to breakdown the sort of chemical bonds that are found in naturally occurring materials.
Synthetic polymers, such as polyethylene and polypropylene, which are commonly used to make plastic bags and other packaging materials have only been in existence for the past 100 - 120 years. Before that, molecules consisting of very long fully saturated chains of carbon-carbon bonds simply didn't exist. As a result, microorganisms may come into contract with plastics but they simply ignore them.
On the other hand, polysaccharides such as cellulose have been in existence as natural products for millions of years, so microorganisms have had sufficient time to evolve so as to break them down.
