For each strain, nitrogen concentration affected the fermentation length, maximum fermentation rate and final biomass, not specific growth rates, as proposed in literature (Mendes- Ferreira et al. [2004, 2009]; Gardner et al. [2002]; Varela et al. [2004]).
Batch culture kinetics of E. coli DH5α showed similar maximum specific growth rates and final biomass yields in shaken 24-well and shake flask bioreactors and in stirred miniature and 20 L bioreactors at matched kLa values.
The biggest decrease was seen for the xfpk(BB) expressing strain, where both maximum specific growth rate and final biomass decreased about 25% compared to the control strain.
Further analysis of 11 isolates was conducted in YNB liquid cultures where the specific growth rate (μmax) and the final biomass concentration (maximum OD 620 nm) were compared to identify the best-growing isolates.
Both YIGCS1 and YIGLO3 had higher maximum specific growth rates and higher final biomass titers compared with strain YIGS16 (Table 2, Fig. 3a).
Clearly, under low nitrogen, certain direct relationships between the parameters analyzed can be established; the strains that exhibit higher nitrogen consumption rates have a higher final biomass, higher specific growth and maximum fermentation rates, and high succinate concentrations.
For E. coli (1000 rpm, 1 vvm) the maximum specific growth rate, μmax, was 0.68 ± 0.01 h−1 and the final biomass concentration obtained, Xfinal, was 3.8 ± 0.05 g L−1.
Final biomass concentrations of 100 and 120 gDCW L-1, and maximum enzyme productivities of 7800 and 5556 IU L-1 h-1, were achieved for high cell density cultures using complex and defined media, respectively.
With respect to biomass cultivation, temperature affected biomass productivity but not final biomass concentration.
Under diurnal light, final biomass titer of 5.79 g L−1 and overall biomass productivity of 1.29 g L−1 day−1 were observed.
