Answered Jul 31, 2019
You wouldn’t necessarily “make” microbes that can do this.
There is at least one species of fungus that can break down certain types of plastic to use for food.
However, there are various problems. Some of which are biological, and some are physical.
The “plastic-eating fungus” uses enzymes called esterases, which will only work on certain classes of polymers that are structured a certain way.
Also, a chunk of plastic will only be vulnerable to reactions on its surface, which might take a long time to eat all the way through. Plus, if I recall correctly, there is a physics thing called “water activity”, which is necessary for the enzymes to work, but is going on at very low levels on the surface of the plastic (even with the fungus and/or enzymes present).
Attempting to insert the enzyme gene into bacteria for mass production has various biological problems, including protein folding, toxicity to the bacteria, etc.