From Cellular Function to Industrial Products
43
Year
Figure 2.10
Increase in productivity, in the period between 1962 and 1987, (output rate/unit volume,
arbitrary units) of penicillin G production by Gist-brocades, Delft (now DSM). The introduction of new
strains is marked with arrows.
With the rapid development in recombinant DNA technology it has, however, become possible
to apply a more directed approach to strain improvement. This is often referred to as
metabolic
engineering,
but terms like molecular breeding or cellular engineering have also been applied.
Several different definitions have been given for metabolic engineering, but they all convey
similar meanings that are captured in the definition:
the directed improvement o f product
formation
or
cellular properties
through
the
modifications
o f specific
biochemical
or
introduction o f new one(s) with the use o f recombinant DNA technology.
Among the applications
of metabolic engineering are:
Heterologous
protein
production.
Examples
are
found
in
the
production
of
pharmaceutical proteins (hormones, antibodies, vaccines
etc.)
and in the production of
novel enzymes. Initially the heterologous gene needs to be inserted in the production
host. Subsequently it is often necessary to engineer the protein synthesis pathway,
e.g,
to
have an efficient glycosylation or secretion of the protein from the cell. In some cases it
may also be necessary to engineer the strain to obtain an improved productivity.
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