Scale-up strategies for packed-bed bioreactors for solid-state fermentation

Two approaches are compared for scale-up of solid-state fermentation proces ses in packed-bed bioreactors, one based on a dynamic heat transfer model, and the other based on a modified Damkohler number. A critical bed height i s proposed, being the maximum bed height which can be used without undesira ble temperatures being reached in the substrate bed during the fermentation . It depends on the microbial specific growth rate, as well as the superfic ial velocity and inlet temperature of the air. The critical heights predict ed by the two approaches are almost identical suggesting that approaches to scaling-up packed-bed bioreactors based on the modified Damkohler number m ay be successful. The modified Damkohler number is then used to predict how simple rules of scale-up might perform. Superficial velocities will need t o increase with scale, although for practical reasons, it is not possible t o increase superficial velocity in direct proportion to height indefinitely . A strategy is proposed to guide experimental programs for scaling-up of p acked-bed bioreactors. (C) 1999 Elsevier Science Ltd. All rights reserved.