4. Conclusion
The results clearly showed that the proposed unstructured
mathematical model satisfactorily predicted the cell growth, substrate
utilization, and HA production for the fermentation with
an initial substrate concentration of 10–60 g l−1. For the substrate
inhibition, the Han and Levenspiel model and the Teissier-type
model gave the best fit for all the systems studied with R2 of 0.997
and 0.985, respectively. All the models tested not only adequately
described the relationship between the principal state variables or
quantitatively explained the behavior of a system, but could also
be used for the design, optimal control, and economic analysis of
HA fermentation processes.