Study on Batch Culture Growth Model for Lactococcus lactis IO-1

L-lactate fermentation employing Lactncoccus lactis IO-1 demonstrated a typical end product inhibition. By numerical analysis of fermentation results of the batch culture of this microorganism, the specific rates for cell growth, substrate consumption and product formation were clearly expressed by the end product inhibition formulae. All constants for those formulae were determined by the fermentation results. A mathematical model for batch culture growth of this microorganism in which the newly defined term α, a ratio of sterile cell formed to total cell population measured by 0. D., was used was constructed. By using this model, computer simulation was carried out and the batch culture growth gave satisfactory approximation to the observed results on the viable cell basis. However, the model gave a deviation from the observed results at the end phase of the fermentation. Further experiment showed that LDH activity in broth, the key enzyme of this fermentation, decreased with a constant decreasing rate which is smaller than cy. Simulation program using enzyme decreasing rate gave perfect results that agreed with the observed results for the whole phase of the fermentation