Introduction: Growth and multiplication of host organisms used as expression system, requires a suitable biochemical and biophysical conditions. The biochemical (nutritional) conditions can be provided by the use of various nutrient media. Depending upon the special needs, different types of media have been developed for expression system to achieve growth, multiplication and over-expression of protein.

Growth Media for Bacterial Expression System

Bacterial expression systems are mainly utilized for protein over-expression because of its rapid growth rate, low cost, ease of high-cell-density fermentation, and availability of excellent genetic tools. Growth of bacterial expression system requires different types of media based on the requirement which can be divided into either complex or defined media. The complex media comprises of natural substances and rich in nutrients therefore suitable for culturing fastidious organism (Table 8.1). On the other hand, defined media are simple and made up of known components put together in the required amounts (Table 8.2).

Preparation of Bacterial Expression media: The composition of the selected bacterial expression media is given in Table 8.2. For preparation of bacterial media dissolve the components in 1 liter of distilled water. Cover the top of the flask with cotton plug or aluminium foil and autoclave the solution at 121°C for 20 minutes. The various antibiotics or nutrient supplement should be added to the media when the temperature is less than 50°C after autoclaving (Figure 8.1).