Answer: Microbial enzymes work under mild conditions, are highly specific and do not pollute the environment.
Enzymes obtained from microbes such as bacteria and fungi catalyse reactions at ordinary temperature and pressure, so a great deal of energy is saved. They act only on one particular substance, so unwanted by-products are not formed and the product is pure. They are used in small amounts, can be produced cheaply on a large scale, are biodegradable and replace harmful chemicals and strong acids, so they reduce pollution. Hence they are preferred to chemical catalysts.