MODELING BATCH-PRODUCTION OF SINGLE-CELL PROTEIN FROM CHEESE WHEY .3. OXYGEN UTILIZATION

A mathematical model capable of describing the oxygen utilization by the yeast Kluyveromyces fragilis during the batch aerobic fermentation of cheese whey was developed. The model predicted the experimental results with R2 of 0.97. The dissolved oxygen concentration in the fermenter was affected by the number of yeast cells present in the system. The dissolved oxygen curve displayed four distinct stages which corresponded to the lag, exponential, stationary, and death phases of the yeast growth curve. A steady state condition was observed during the stationary phase, during which the oxygen uptake rate by the yeast was equivalent to the oxygen added to the system by the aeration equipment. The mathematical model showed that the oxygen concentration would increase during the death phase and the initial dissolved oxygen concentration would be achieved after 80 h. The specific oxygen uptake rates for the lag, exponential, stationary and death phases were 0. 3200 x 10(-12), 2.1400 x 10(-12), 0.5100 X 10(-12), and 0.0028 x 10(-12) Mg O2 cell-1 h-1, respectively.