BIOTECHNOLOGY - V. H. Herasymenko - 2006

Part II. Specialized Biotechnologies

Chapter 20. BIOTECHNOLOGY OF ENZYME PRODUCTION

20.2. METHODS OF CULTIVATING MICROORGANISM ENZYME PRODUCERS

Depending on The Nature of the cultivation process for microorganism producers, all technological processes for enzyme preparation manufacturing are divided into two fundamentally different groups: in the first case, Fermentation is carried out using a submerged method in a liquid nutrient medium, whereas In the second case, a surface culture is employed, growing on a specially prepared loose and moistened nutrient medium.

Submerged cultivation method for producers. Research in the field of submerged microorganism cultivation began in our country in the 1950s. The method involves growing microorganisms in a liquid nutrient medium. It is technically more advanced than surface cultivation because it is easily amenable to mechanization and automation. Furthermore, all Cells of the culture exist in identical, easily reproducible conditions, ensuring they are uniformly supplied with nutrients and oxygen. Submerged cultivation makes it possible to precisely dose the content of various components in the nutrient medium. By altering the COMPOSITION OF THE medium and the cultivation conditions, the synthesis of certain Enzymes can be significantly enhanced.

The entire cultivation process must be carried out under strict aseptic conditions. On the one hand, this is an advantage of the method; on the other hand, it leads to considerable technical difficulties, as even the slightest breach of asepsis can sometimes result in the complete cessation of enzyme production. Another disadvantage of the method is that the concentration of the enzyme in the medium is significantly lower than in surface culture extracts. Culture liquid filtrates contain no more than 3% dry matter, necessitating preliminary concentration of the filtrates prior to enzyme isolation.

Surface cultivation method for enzyme producers. In the surface method, the culture grows On the surface of a solid, moistened nutrient medium. The mycelium completely envelops and quite firmly binds the solid particles together. Cells obtain Nutrition from the medium's nutrients and utilize atmospheric oxygen for Respiration; therefore, to ensure an adequate oxygen supply, loosening of the entire medium Structure with a shallow layer height is required. This necessitates a large contact surface between the loose medium and the air—in other words, substantial production areas—and, in the absence of mechanization, demands significant manual labor.

In addition, the solid substrates used in this approach are difficult to sterilize, and the surface culture is hard to protect from contamination by extraneous microflora.

Alongside its disadvantages, the surface method also possesses advantages over the submerged technique. Surface cultivation yields a higher rate of microorganism growth and achieves a greater concentration of dry matter. Surface cultures can be quickly and relatively easily dried and converted into commercial forms. Dried surface culture can be stored for long periods and is easy to transport. A very significant advantage is that microorganisms synthesize a broader spectrum of enzymes in surface cultures.