media quoted by Cooney (1981) showed that some nutrients are frequently added in substantial excess of that required, e.g. P, K; however, others are often near limiting values, e.g. Zn, Cu. The concentration of P is deliberately raised in many media to increase the buffering capacity. These points emphasize the need for considerable attention to be given to medium design.

Some micro-organisms cannot synthesize specific nutrients, e.g. amino acids, vitamins or nucleotides. Once a specific growth factor has been identified it can be incorporated into a medium in adequate amounts as a pure compound or as a component of a complex mixture.

The carbon substrate has a dual role in biosythesis and energy generation. The carbon requirement for biomass production under aerobic conditions may be estimated from the cellular yield coefficient (Y) which is defined as:

Quantity of cell dry matter produced Quantity of carbon substrate utilized Some values are given in Table 4.3. Thus for bacteria

Table 4.3. Cellular yield coefficients (Y) of bacteria on different carbon substrates (data from Abbott and Clamen, 1973)


Cellular yield coefficient

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Vinegar For Your Health

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