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

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