Optimization of pulsed feeding in a Baker's yeast process with dissolved oxygen concentration as a control parameter

Abstract

The aim of the study was to optimize nutrient inflow in baker's yeast cultivation where the nutrient was dosed in portions, according to the cyclic changes in dissolved oxygen concentration; the optimization criterion being a simultaneous maximization of biomass yield and specific growth rate. The maximization of such a criterion required that the glucose concentration in the culture medium should be higher than the glucose critical level. Furthermore, the size of the nutrient portion had to be limited, the limiting parameter being the set value of the respiratory quotient. Two factors were found to be of significance to the optimization process: the set value of the respiratory quotient and the dynamics of changes in the portion size. Portions for a real respiratory quotient value below the set value (which was 1.1) and for portion value changes of ±10% were regarded as optimal. The biomass yield and specific growth rate of the culture where the set value of the respiratory quotient totaled 1.1 and the dynamics of changes in the portion size were within the range of ±10% amounted to 0.55 g g −1 and 0.14 h −1, respectively. Initial biomass concentration was also a parameter of major importance to the optimization of nutrient inflow. The increase in the initial biomass concentration value stimulates aerobic fermentation, brought about a decrease in biomass yield and specific growth rate.