CHAPTER III : Industrial culture media

      III.1. Definition

The culture medium is the matrix allowing the growth of microorganisms. It is an aqueous solution in which all the nutrients essential for the growth of microorganisms are dissolved. For industrial production, it is necessary to culture microorganisms in very large quantities in tanks whose volume can reach several cubic meters.

      III.2. Composition of industrial culture media

Culture media used in industrial processes are generally made from raw materials (table 1).

• Carbon source: the best carbon substrates for microorganisms are simple sugars.

• Source of nitrogen: nitrogen is an essential element because it represents the main compound of proteins and nucleic acids. Nitrogen is generally used in the form of ammonia (NH3OH).

• Minerals: are involved in the composition and structure of certain enzymes (P, S, Mg and Fe).

• Growth factor: vitamins, amino acids, nucleotides must be added to cultures if the organism is demanding (from a nutritional point of view)

• Antifoamers: are compounds that prevent or reduce the formation of foam. Their use helps increase productive capacity and the quality of finished products. Controlling and reducing the level of foam improves the efficiency of production processes.

       III.3. Criteria for choosing the raw material used in industrial environments :

1. Price: the raw material must be as low cost as possible.

2. Abundance and availability.

3. Cost of transport: being close to the production unit.

4. Ease of processing its discharge after use: the cost of processing the discharge and reuse in another production must be taken into consideration.

5. Uniformity of raw material quality.

6. Adequate chemical composition: adequate amount of carbon for optimal growth, nitrogen, salts and vitamin.