A complementary approach to scale-up

Abstract

A typical batch process may be subdivided into:

• a) continuous sterilization of culture medium

• b) aeration and agitation in bioreactor vessel

• c) ancillary operations and equipment.

Assuming that the accumulation rate of specific product in the broth and the annual output of the product are given, objective functions defined by the sum of annual expenditures on utilities and equipment may be simulated, and optimized via the golden section method with respect to a) and b).

The modified complex method may be applied to minimize the objective function for the whole batch process, using as design variables the working volume of bioreactor, process time and boiler capacity.

Optimization becomes increasingly beneficial as the magnitude of the objective function increases. This means that optimization of each individual operation or item of equipment in the process (i. e., suboptimization which disregards the mutual relationships among items constituting the process) becomes less important from the viewpoint of process synthesis. The significance of the “synthetic” approach, complementary to the usual “analytical” approach to scale-up is emphasized.