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From Cellular Function to Industrial Products
The Biotech industry is one of the fastest growing industrial sectors, and in recent years many new
products have been launched. Thus, many new pharmaceuticals are currently produced based on
growth of microbial and cell cultures, but also - to the benefit of the environment - many classical
chemical products are today produced through recruitment of cell factories. The exploitation of cell
cultures for production of industrial products involves growth of the cells in so-called bioreactors,
and this is often referred to as a fermentation process. The term fermentation is derived from Latin
fervere,
to boil, and it has been used to describe the metabolism of sugars by microorganisms
since ancient times. Thus fermentation of fruits is so old that ancient Greeks attributed its
discovery to one of their gods, Dionysos. Among the classical fermentation processes are: beer
brewing, which is documented to have been widely known 3000 years B.C. in Babylonia, soy
sauce production in Japan and China, and fermented milk beverages in the Balkans and in
Central Asia. Before WWII fermentation processes, however, mainly found their application in
the production of food and beverages, and it was only after the introduction of the penicillin
production in the late 1940’s that large-scale fermentation found a use in the production of
pharmaceuticals. Today fermentation processes are used in the production of a broad spectrum of
products and these processes can be divided into seven categories according to the product made
(Table 2.1). Besides the use of fermentation processes for the production of specific products,
these processes are also used extensively for specific biotransformations, e.g., in the conversion
of sorbose to sorbitol (an important step in the chemical synthesis of vitamin C), as they offer the
possibility to perform site-specific chemical modifications. Thus, in the production of complex
molecules with one or more chiral centers the use of whole cells to carry out specific
biotransformations offers unique possibilities, and today many fine chemicals are produced using
specific biotransformations. Another area where microbial cultures are extensively used is in the
environmental sector, to clean wastewater and contaminated soil. Here the product is clean water
and decontaminated soil.
A key issue in the design of novel fermentation processes, and in the optimization of existing
fermentation processes is a quantitative description of the cellular reactions that play an important
role in each particular cell factory and of the processes by which the cells interact with the
environment imposed on them through the bioreactor operation. These aspects are the essence of
this whole textbook, but in this chapter we give a short overview of the processes underlying
cellular function and some general aspects concerning design of fermentation processes.
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