Continuous Cultivation of Microorganisms

Continuous culture can outperform batch culture by eliminating the inherent down time for cleaning and sterilization and the long lags before the organisms enter a brief period of high productivity. The following graph shows typical batch operation where the fermenter is used over and over again:

Note that there is a small percentage of the total time in which the rate of product formation is near its maximum. It is sometimes possible to maintain very high rates of product formation for long times with continuous cultivation. Continuous culture is superior to batch culture in several ways for research. Interpretation of results is difficult for batch culture because of changing concentrations of products and reactants, varying pH and redox potential, and a complicated mix of growing, dying, and dead cells. Data from continuous cultures have much less complexity because there are dynamic equilibria or small excursions from steady state. Cause and effect relationships tend to be obvious. Although continuous culture gets much more productivity from the bioreactor, there is not so great an improvement over batch culture in terms of the total amount of tanks and resources because there must be equipment for make up and sterilization to support the continuously operated vessel.