Corynebacterium glutamicum - JUWEL - Forschungszentrum Jülich

5. L-Valine Production Process Development
5.1.2. Media
For all media, the used water was demineralized by reverse osmosis. The components
were dissolved in demineralized water and sterilized by by filtration or by autoclavation
for 20 minutes at 121 ◦ C. A syringe with a sterile filter (acrodisc � 0.2 µm, Pall Corporation,
Ann Arbor, USA) was used for filtration of small volumes for use in shake flasks.
The filter sterilized solutions for use in the stirred bioreactor were pumped through a filter
which was autoclaved together with the bioreactor (0.2µm Sartobran � -300, Sartorius
AG, Göttingen, Germany).
Complex Medium
Complex medium CGIII (Keilhauer et al., 1993) was used for the first preculture, which
was inoculated directly with frozen working seed lots. The composition of this medium
is mentioned in table 5.1. This medium was also used for the production of the seed
lots.
Table 5.1.: Composition of the Complex Medium for the first preculture.
Substance Concentration
glucose.H2O 22 g.L −1
NaCl 5 g.L −1
peptone 10 g.L −1
yeast extract 10 g.L −1
kanamycin stock solution 1 mL.L −1
The glucose was dissolved and autoclaved separately. The kanamycin stock was sterilized
by filtration. All other components were autoclaved together.
Defined Medium
The composition of the used defined culture medium was adapted from the minimal
medium CGXII (Keilhauer et al., 1993; Morbach et al., 1996), which was also used during
strain development at the IBT1 of the research centre. In some points, this medium
was not ideal for our purposes or for an industrial production process, so some changes
were made.
The trace element composition was taken from the composition which was optimized
for another strain of C. glutamicum (WeusterBotz et al., 1997).
The composition of the medium is shown in table 5.2 on page 92.
In the precultures, also 5 g/L urea was added in order to keep the pH from decreasing
too fast too soon. This amount of urea was also used during development of the strain
but removed from the final medium composition because it caused the pH to rise rather
fast in the first phase of the experiments (data not shown). This increase in pH depends
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