Elfect of dissolved oxygen on cell density
When the dissolved oxygen was bclow 255/c, the cell
concentrations increased with an increase in dissolved
oxygen, but when the dissolved oxygen was above 25%
no further increase in cell concentration was achieved,
i.e. about 25% of dissolved oxygen is the critical level
for respiration of Escherichia coil (Fig. 2). The fol-
lowing equation is used to fit the relationship between
cell density (X,g/l) and dissolved oxygen (d,g2):
X= -0.1302d-'+6.5211d+38.4107, r=0.9579. (3)
The fitting rcsult was satisfactory (Fig. 2). Thc
maximum ccll density Xm = 120.0634 g/I can be arrived
at dissolved oxygen d = 25.0426%.
Comparison hetween high cell density.fermentation and
normal fi'rmentation
Figure 3 demonstrates that high cell density fermenta-
tion had a shorter fermentation cycle (10 h) and higher