Production of microbial enzymes (1)

1.    Culture media

Different culture media have different specific growth rate and static formation ability of microorganisms. Therefore, providing appropriate and abundant nutrients in the culture media is an important prerequisite for the growth of bacteria and the mass production of enzymes. 

The raw materials used in the preparation mainly include carbon sources (including rapidly utilized monosaccharides, disaccharides, and slowly utilized polysaccharides such as starch and cellulose), ammonia sources (including soybean cake powder, peanut cypress, fish meal, silkworm pupa powder, and yeast powder , Corn steep liquor and other organic ammonia sources and ammonium salts, nitrates and other inorganic nitrogen sources), inorganic salts and inducers, solid fermentation often requires adding a certain amount of ventilated carriers such as rice husks and corn husks. 

Practice has proved that the ratio of carbon source to nitrogen source in the culture medium, usually expressed as C/N, directly affects the growth, reproduction and enzyme production of bacteria. 

When the C/N ratio is too small, that is, there is too much ammonia source in the culture medium, causing excessive growth of microorganisms, and insufficient carbon source supply, which easily causes bacterial senescence and autolysis, resulting in waste of ammonia source and decreased enzyme production; if C The ratio of /N is too high, that is, the nitrogen source is insufficient, and the microorganisms grow too slowly. 

On the one hand, it is easy to cause the infection of bacteria. On the other hand, because there are not enough microorganisms to produce, it will also cause the carbon source grain cost and enzyme production to decrease. 

Therefore, the appropriate C/N ratio should be selected appropriately according to the characteristics of various microorganisms, which is an important factor in improving enzyme production.

Most of the microbial enzymes used in the feed industry belong to the category of induced enzymes, so adding an inducer to the culture medium will increase the output of extracellular enzymes. 

For example, adding sophorose can induce the production of Trichoderma cellulosae, and xylose induces hemicellulase. 

However, the price of inducer is often more expensive. In actual production, cheap raw materials containing inducer are usually added instead. 

For example, the seed coat of some plants such as Sophorae contains sophorose, and the corn cob is rich in xylose. It can be hydrolyzed to produce sophorose and xylose.

2.    Requirements of enzyme-producing microorganisms

The bacteria used in the production of enzyme preparations should be able to use relatively cheap and simple and raw materials, and the wider the diet, the better, easy to grow without the addition of inducers, and grow rapidly;
the produced enzymes are easy to separate, purify and concentrate, and the enzyme activity should be high, with good stability, and a wide spectrum of activity;
enzyme-producing microorganisms should have stable physiological characteristics and not form toxic or immunogenic metabolites.

In particular, it should be noted that all enzyme-producing strains must be tested for toxicity, except for those that are recognized as safe strains.