The impact of fluid-dynamic stress in stirred tank bioreactors on the synthesis of cellulases by Trichoderma reesei at the intracellular and extracellular levels

Abstract

Cellulases for bioethanol production are mainly made by fed-batch fermentation using a filamentous fungus, Trichoderma reesei. Agitation at different scales impacts on morphology, rheology and growth rate and can be correlated by EDCFεmax. Typically, EDCFεmax is much smaller at commercial scale and fungal size, viscosity and growth rate are greater. Here, to increase understanding, continuous culture in 3 L bioreactors using two EDCFεmax values were undertaken. The higher EDCFεmax decreased the cellulase production (concentration, 21%; specific production rate, 24%; protein yield, 20%) whilst proteomic analysis showed, at an intracellular level, a decrease of cellulase and hemicellulase synthesis. An increase of stress proteins also occurred, which may help cells to limit the impact of fluid dynamic stress. Also, cellulase production during continuous culture at the bench varied with EDCFεmax similarly to that between bench and commercial scale during fed-batch culture.