38
Chapter 2
roughly be divided into four phases (see Fig. 2.9). First the product is identified. In the case of a
pharmaceutical this may be a result of random screening for different therapeutic effects by
microbial metabolites,
e.g.
by high throughput screening of secondary metabolites from
Actinomycetes,
or it may be the result of a targeted identification of a novel product,
e.g.
a
peptide hormone with known function. Outside the pharmaceutical sector the product may also
be chosen after a random screening procedure,
e.g.
screening for a novel enzyme to be used in
detergents, or it may be chosen in a more rational fashion. With the rapid progress in genomic
sequencing programs, it is now possible to search for new target proteins directly in the
sequenced genomes by using bioinformatics.
When the product has been identified the next step is to choose or construct the strain to be used
for production, and thereafter follows design of the process. This involves choosing an
appropriate fermentation medium and the optimal process conditions. In parallel to the design of
the production process further research, e.g. clinical tests, is done in order to have the product
approved. When the strain has been constructed one of the first aims is therefore to produce
sufficient cell material for further research, and this is typically done in pilot plant facilities. For
a pharmaceutical compound sufficient material must be produced for clinical trials. For other
products it may be necessary to carry out tests of the product and examine any possible toxic
effects. The final steps in the development are product approval by the proper authorities and
construction of the production facility (which in some cases may be through retrofitting of an
existing plant). In the following we will consider some of the different aspects on process
development as an introduction to the more detailed quantitative analysis that will be introduced
in the later chapters.
2.2.1 Strain Design and Selection
A key step in the development phase of a fermentation process is to choose an appropriate strain.
In the past this choice was normally obvious after the product had been identified,
e.g. P.
chrysogenum
was chosen for penicillin production since it was this organism that was first
Identify
Chose/
product
construct strain
Produce
material for
research
— ►
Product approval
Design
Production
process
Optimize
production
process
0
Time for process development
5-15 years
Figure 2.9
Different phases in the development of a fermentation process.
previous page 61 Bioreaction Engineering Principles, Second Edition  read online next page 63 Bioreaction Engineering Principles, Second Edition  read online Home Toggle text on/off