Fermentation

In the continuous systems, such as continuous beer fermentation, immobilized cells are kept inside the bioreactor for long periods of time. Thus an important factor in the design and performance of the immobilized yeast reactor is immobilized cell viability and physiology. Both the decreasing specific glucose consumption rate (qim) and intracellular redox potential of the cells immobilized to spent grains during continuous cultivation in bubble-column reactor implied alterations in cell physiology. It was hypothesized that the changes of the physiological state of the immobilized brewing yeast were due to the aging process to which the immobilized yeast are exposed in the continuous reactor. The amount of an actively growing fraction (Xim act) of the total immobilized biomass (Xim) was subsequently estimated at approximately Xim act) 0.12 gIB gC-1 (IB) dry immobilized biomass, C) dry carrier). A mathematical model of the immobilized yeast biofilm growth on the surface of spent grain particles base