GAS HOLDUP AND LIQUID CIRCULATION RATE IN CONCENTRIC-TUBE AIRLIFT BIOREACTORS

A model gas holdup and liquid circulation rate is presented for airlift bioreactors based on a drift -flux model and an energy balance that takes into account the physical interactions between the liquid, the gas bubbles and the liquid-wake associated with the bubbles. A 250 l pilot-scale concentric cylinder airlift bioreactor is used to obtain gas holdup and liquid circulation data for the fermentation of a Newtonian (Saccharomyces cerevisiae) and a non-Newtonian (Saccharopolyspora erythraea) culture. The data are interpreted in terms of the model equations and the agreement between the two is considered to be good.