The kinetics and mechanism of Corynebacterium glutamicum aggregate breakupin bioreactors

Cultivation of bacteria requires high levels of agitation and aeration to s atisfy the mass transfer requirements of the cells. Associated with these c onditions are turbulent forces which may act on the surfaces of cells and b e detrimental to their growth, metabolism and morphology. The kinetics and mechanism of hydrodynamic trauma has been investigated for the breakup of a ggregates of Corynebacterium glutamicum (A TCC 13032) in a stirred-tank rea ctor and a capillary flow loop system. The effect of forces associated with turbulent eddies in the impeller discharge zone of the stirred tank reacto r has been compared with that of collapsing air bubbles at the air medium i nterface. A model is presented to describe the initial rate of aggregate br eakup caused by fluid-aggregate interactions. It assumes that aggregate dis ruption is caused by the interaction of aggregates with similarly sized tur bulent eddies. The extent of aggregate breakup is a function of the magnitu de of the turbulent force as well as the total duration of the force event. The applicability of the model to animal cell systems has been investigate d. Results showed that both the interaction of microbial cells with turbule nt eddies in the viscous dissipation subrange in the impeller discharge zon e, as well as with collapsing air bubbles at the air medium interface contr ibuted to the total force acting on the cells. (C) 1999 Elsevier Science Lt d. All rights reserved.