full issue - Association of Biotechnology and Pharmacy

Current Trends in Biotechnology and Pharmacy
Vol. 5 (3) 1298 -1308 July 2011, ISSN 0973-8916 (Print), 2230-7303 (Online)
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while it was 5.3×10 6 cells/ml in the control
(culture medium without excess ammonium).
Therefore, the threshold concentration of
ammonium for the rCHO cells is 6 mM. The
effect of ammonium stress on the activity of
rhFVIII is shown in Table 2. Recombinant
protein production was completely stopped at 11
mM NH 4
Cl.
Cell density 10 6 cells/ml
Ammonium concentration
Fig. 4. The effect of ammonium concentration on the
rCHO cell density
Table 2. Activity of rhFVIII under ammonium stress
Ammonium rhFVIII Ammonium rhFVIII
concentration activity concentration activity
(mM) (%) (mM) (%)
Control 6.4 9 2.6
2 4.4 10 2.1
4 4.1 11 0
6 3.2 12 0
To mitigate the adverse effects of
ammonium, some amino acids were selected and
then added to the culture medium. According to
the isoelectric point of amino acids and their role
in metabolic pathways related to ammonium
formation (14), four amino acids consisting of
proline, threonine, glycine and asparagine were
selected. As it is shown in Figure 5, proline and
glycine increased the ammonium-stressed rCHO
cell density by up to 24% and 28 % (ANOVA,
p