The food we eat is very miscellaneous. In addition to starch, protein, fat and so on, what do we use to digest them? In addition to teeth chewing and grinding, gastrointestinal peristalsis and other mechanical movements, we mainly rely on our own stomach acid and various digestive enzymes to decompose and digest food. Those that can digest protein must be protease, and those that can digest fat and oil must be lipase. As for cellulose, we humans can't digest it, but cellulose can slow down the intestine, while cattle and sheep can digest it. I think there must be cellulase in the stomach of cattle and sheep.

Biological enzyme is extracted from living things. Animals, plants and microorganisms in nature are the source of enzyme. For example, papain, bromelain, soybean lipoxygenase and maltamylase from plants. The animal enzymes used are trypsin and pepsin. But only a few plants and animals are economic enzyme sources, most of which are obtained by microorganisms. Moreover, the enzymes from animals and plants are more precious, which are mostly used in food and medicine. At present, more than 1000 kinds of enzymes have been found, only dozens of enzymes are commonly used in industry, and only 20 kinds are produced in large quantities. However, amylase, protease and lipase are often used in industry.

Microorganism is an important source of enzyme preparation. Because there are many kinds of microorganisms growing fast and low cost, they are suitable for the production of biological enzymes. Under suitable conditions, bacteria can reproduce in 20-30min, and its growth rate is 500 times of that of crops and 1000 times of that of livestock. In addition, there are many kinds of microorganisms. Microorganisms living in different environments have different metabolic pathways and can produce different enzyme molecules. For example, high temperature enzyme, medium temperature enzyme, low temperature enzyme, high salt resistant enzyme, acid resistant enzyme, alkali resistant enzyme and so on are all extracted and cultured in special living environment.

The conclusion is that biological enzyme is around us. It is not a strange thing, but it is very useful for our production and life.