4. Fermentation kinetics of YL-C11
Establishing a preliminary kinetic model to investigate cell growth in all kinds of fermentation environments would be well utilized in directing scale production. Although the feed will slightly increase the volume of the fermentation broth, the volume of the fermentation broth was considered to be constant due to sampling in this study.
4.1Kinetics of cell growth
Figure 5 shows the time courses of biomass separately derived from the model equations and the experiments. Figures 5a and 5b show the fitting results from the fed-batch fermentation and DO-stat fed-batch fermentation, respectively. The cell growth showed an “S” pattern. The cell growth curve of YL-C11 was consistent with the logistic equation, which was presented as follows:
\(\frac{\text{dX}}{\text{dt}}=\mu_{m}(1-\frac{X}{X_{m}})X\) (1)
Where X is the biomass concentration (g/L), t is fermentation time (h), dX/dt is cell growth rate [g/(L h)]. µmax(h-1) is maximum specific growth rate, and Xm is the maximum microorganism concentration (g/L).
The simulated kinetic parameters were listed in Table 1. The models fit the experimental data well with R2 values of 0.9315 for fed-batch fermentation and 0.9526 for DO-stat fed-batch fermentation, indicating the adequacy of the logistic equation model to fit experimental data. The μm value in DO-stat fed-batch fermentation is 0.49, which is higher than that in fed-batch fermentation (0.113). This result suggests that DO-stat fed-batch fermentation resulted in a higher cell growth rate, thus, more biomass was obtained.