The proteins that catalyse the biological reactions inside a living cell are called enzyme. These are the globular proteins that are secreted by cells to regulate the metabolic reactions. Basically enzymes are of two types: intracellular enzymes and extracellular enzymes.
The intracellular enzymes are produced inside the cell and catalyses the biological reactions within the cell, whereas the extracellular enzyme is produced within the cells but secreted outside the cell wall which catalyses the biological reactions.
There are different types of organisms such as bacteria, fungi, actinomycetes and plant and animal cells which are capable of producing diverse types of enzymes (Table 6.3). Several microorganisms have been discovered and commercially exploited in recent years. Besides, animal cell lines have also been developed for the production of novel products.
1. Selection of Enzyme-producing Microorganisms/Cells :
Although all organisms produce both intracellular and extracellular enzymes that are required to carry out their life, yet only such microorganisms/plant or animal cells are selected that produce maximum amount of desired enzymes.
Such organisms and cells are selected, identified and characterized. Diagram of A. oryzae that produces diastase (a digestive enzyme).
It should be noted that the selected microorganisms should bear the following features:
(i) The selected microorganism must be nonpathogenic.
(ii) They should accumulate large amount of enzyme in the medium.
(iii) They should rapidly produce the enzyme in medium.
(iv) They must be able to grow and produce enzyme utilizing cheaper substrate.
(v) They must be stable at given temperature, pH, etc.
Recombinant microorganisms are now becoming the dominant source for enzymes for a wide variety of types.
2. Methods for Enzyme Production:
Based on requirement there are different method of enzyme production. However, submerged culture is applied for large scale production of enzymes. In this method medium is formulated (see upstreaming process given earlier) and pumped into a fermentor.
Previously characterized inoculum is added into the fermentor. Physico-chemical conditions of the medium are maintained by adjusting the pH, temperature, aeration, etc. During the course of time the desired microbe grows and produces the enzyme. Then the fermented broth is taken out and desired enzyme is isolated.
Various stages of downstream processing have been given earlier in Fig. 6.7 which also applies for enzyme purification also.