C h a p ter 2
human insulin, it is important that the production costs are kept low, which requires an expression
system with a high productivity,
i. e. E. coli
For very complex molecules like tissue
plasminogen activator (tPA) and erythropoietin (EPO) it is, however, not possible to obtain
sufficiently active compounds in microbial systems, and here a higher eukaryotic expression system
An important aspect in design of a fermentation process is the choice of fermentation medium,
which represents the raw material for the process. The fermentation medium should fulfill the
It should contain a carbon, nitrogen and energy source.
It should contain all essential minerals required for growth.
It should contain all necessary growth factors to ensure rapid growth and high yield of the
It should be of a consistent quality and be readily available throughout the year.
It causes a minimum of problems in the downstream processing.
It causes a minimum of problems in other aspects related to the fermentation process, i.e.,
it has no negative effect on the gas-liquid mass transfer.
Traditionally complex media from the agricultural sector were used, as these were present in
large quantities and were relatively cheap. Table 2.9 lists some typical complex media
components used in the fermentation industry together with some typical products produced
using the different media.
The advantages of applying complex media are that they often contain an organic nitrogen
source, essential minerals and different growth factors. Thus, two frequently applied complex
media, com steep liquor and pharmamedia; both contain a large variety of amino acids, many
different minerals and many different vitamins. The disadvantages of complex media are that: 1)
there may be a seasonal variation in the composition, 2) the composition changes with storage,
Table 2.9 Complex fermentation media often applied in the fermentation industry.
Com steep liquor
Lactate, amino acids, minerals,
Starch processing from
Sucrose, raffinose, glucose,
Sugar cane or sugar beet
Bakers yeast, ethanol
Carbohydrates, minerals, amino
acids, vitamins, fats
Amino acids, growth factors
Pentides. amino acids, vitamins