This article concerns the comparison between batch and fed-batch fermentation based on productivity and including the analysis of the implications on product manufacturing cost.
The calculation method of productivity is based on the assumption that batch production rate data are applicable to fed-batch fermentation and that, within a certain range of concentrations, the percent rate of change of batch production rate with respect to time is proportional to the difference of product concentration at maximum production rate minus instant concentration.
General correlations are developed and plotted in diagrams for easy practical application of the proposed method of calculation.
Correlations so established may find application to design and to planning and control of operating conditions of fermentation plants.
Example calculations refer to penicillin G production. List of symbols c BU/m 3 or kg/m 3 product concentration D 1/h dilution rate K 1/h 2 proportionality constant n -number of withdrawals p BU/m3h or kg/m3h productivity r BU/m3h or kg/m3h production rate t h time V -withdrawal volume ratio to instant liquid volume inside fermenter BU = zo 9 I.U. = one billion of international units. Subscripts B Batch fermentation D Fed-batch fermentation i ith withdrawal m maximum production rate o dead time 1 initial withdrawal max maximum productivity