Q1.
Do you know any fungus that can degrade plastic?
Answer
Yes — several are known. The best-studied are:
- Aspergillus tubingensis — a relative of the very Aspergillus in Fig. 11.8, isolated in 2017 from a rubbish dump in Islamabad. It grows on polyester polyurethane and breaks it down in a matter of weeks.
- Pestalotiopsis microspora — found in the Amazon rainforest. It can live on polyurethane as its only food, and remarkably it can do so even without oxygen, which is the condition deep inside a landfill.
- Aspergillus flavus and several Penicillium species — these attack polythene film, though slowly.
Why a fungus can do this at all: a fungus feeds by secreting enzymes outside its body and absorbing the small molecules that result — exactly what the hyphae did to the starch of your bread. Plastics such as polyurethane and polyester are long chains held together by ester and urethane linkages, which are chemically not so different from the linkages in natural polymers. Fungal enzymes (esterases, cutinases, laccases) can cut those linkages, chopping the chain into fragments small enough for the hyphae to take in and respire. The plastic literally becomes the fungus's food.
Tip: do not treat this as a solution to the plastic problem. It works on some plastics and not others, it is slow, and it needs controlled warmth and moisture. Reducing, reusing and segregating plastic is still far more effective than hoping a fungus will eat it.