Medium formulation is an essential stage in the design of fermentation process. Most fermentation media require liquid media, although some solid-substrate fermentations are also operated. Fermentation media must satisfy all the nutritional requirements of the microorganisms and fulfill the technical objectives of the process. There are several stages where media are required in a fermentation process; inoculum (starter culture), propagation steps, pilot-scale fermentations and the main production fermentations. According to Cruger W and Cruger A (1990); on a large scale, the sources of nutrients should be selected to create a medium which should meet as many as many possible of the following criteria: i.
It should produce the maximum yield of product or biomass per gm of substrate used. ii.
It should produce maximum concentration of product or biomass. iii.
It should permit the maximum rate of product formation. iv.
There should be the minimum yield of undesired products. v.
It should be of a consistent quality and be readily available throughout the year. vi.
It should cause minimal problems during media preparation and sterilization. vii.
It should cause minimal problems in other aspects of the production process particularly aeration and agitation, extraction, purification and waste treatment. The initial step in media for media formulation is the examination of the overall process on the stoichiometery for growth and product formation. The optimization of a medium should be carried out such that it meets as many as possible of the seven criteria. Different combinations and sequences of process conditions have to be investigated to determine growth conditions (Stanbury P.F and Whitaker A; 1995). Medium optimization can be carried by the classical method, in which one independent variable is changed while keeping all others at a certain level. An aerobic fermentation process may be represented as: Carbon and energy source + Nitrogen source + O2 + other...
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