BIOTECHNOLOGICAL PLATFORMS - Bioengineering for Pollution Prevention - page 22

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B. B IOREACTOR E CHNOLOGIES [45]
1. Introduction
All bioreactors have in common the central purpose of maintaining ideal conditions for
one or more species of microbes, such that the maximum desired activity is promoted.
Bioreactors are essential elements in all industrial processes that make use of microbial
growth and metabolism with the expectation that the future success of commercial
biotechnology depends significantly on the advancement of bioreactor technology [1]. Basic
bioreactor design has changed little, however, in the past 40 years, possibly due to an absence
of sufficient market forces. Currently, more than 50 percent of all commercial bioreactors are
used in the synthesis of low-volume, high-value products, such as pharmaceuticals, that may
be synthesized profitably without stringent process optimization. In contrast, the productions
of high-volume, low-value products such as biomaterials and fuels carry sufficiently low
profit margins that a high degree of optimization is essential. Because the latter class of
products has the greatest potential for positive environmental impact, bioreactor design and
optimization represent important priorities in the advancement of bioengineering for pollution
prevention.
1.1. Reactor Conditions
Successful design and operation of bioreactors requires optimization of numerous
quantities, including such conditions as pH, substrate and product concentrations, cell density,
oxygen concentration, and temperature. Understanding the roles of each of these in a
particular bioprocess, as well as predicting and controlling their spatial and temporal variation
within narrow limits throughout the bioreactor volume, is of central importance to reactor