Fed batch fermentation

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Fed-batch culture is, in the broadest sense, defined as an operational technique in biotechnological processes where one or more nutrients (substrates) are fed (supplied) to the bioreactor during cultivation and in which the product(s) remain in the bioreactor until the end of the run.[1] It is also known as semi-batch culture. In some cases, all the nutrients are fed into the bioreactor. The advantage of the fed-batch culture is that one can control concentration of fed-substrate in the culture liquid at arbitrarily desired levels ( in many cases, at low levels).

Generally speaking, fed-batch culture is superior to conventional batch culture when controlling concentrations of a nutrient (or nutrients) affect the yield or productivity of the desired metabolite.

The types of bioprocesses for which fed-batch culture is effective can be summarized as follows:

1. Substrate inhibition[1]

Nutrients such as methanol, ethanol, acetic acid, and aromatic compounds inhibit the growth of microorganisms even at relatively low concentrations. By adding such substrates properly lag-time can be shortened and the inhibition of the cell growth markedly reduced.

2. High cell density (High cell concentration)[1]

To achieve very high cell concentrations, e.g. 50-100 g of dry cells/L, in a batch culture a high initial concentrations of the nutrients in the medium are needed. At such high concentrations of the nutrients become inhibitory, even though they have no such effect at the normal concentrations used in batch cultures.