1.1. Environmental design
Environmental design is concerned with the determination of the reaction conditions needed for formation of the required product, being mostly interested in obtaining the maximum economic yield, which includes product separation as well as product formation. Reaction conditions include
pH, temperature, dissolved oxygen, water activity, nutrients availability and supply of precursors and substrates for product formation.
One concern associated with the presence of these precursors and substrates is the homogeneity, so that all parts of the reactor system are provided with the required environment. All these factors are likely to vary with the time of the fermentation process. The controlled variation of the reaction environment should be then developed as an important tool of process enhancement.
The control should take into account the "nature" of the product of interest: the product can be growth-associated, meaning that the formation of the product and biomass are proportional, or the product might be non-growth-associated. Usually, for this case, biomass is initially formed and then conditions are created for the production of the product. and the organism growth and product formation are likely to have different environmental requirements.
The environment should be free of undesirable organisms which may be unproductive or produce substances that are not controlled, unknown and which contaminate the product or inhibit the desired microorganism. The cost and risk of contamination are factors that are usually balanced against the cost of preventing contamination, which can be very expensive.
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