15.2 Production and Scale
In Section 5.7 we considered microbial growth and described the
various stages: lag, exponential, and stationary. Here we describe
microbial growth and product formation in an industrial context.
There are two types of microbial metabolites of interest to
industrial microbiology, primary and secondary. A primary
metabolite forms during the exponential growth phase of the
microorganism. By contrast, a secondary metabolite forms near
the end of growth, frequently at, near, or in the stationary phase
of growth (Figure 15.1).
A typical primary metabolite is alcohol. Ethyl alcohol (ethanol) is a
product of the fermentative metabolism of yeast and certain bacteria
( Section 4.8) and is formed as part of energy metabolism.
Because organisms can grow only if they produce energy, ethanol
forms in parallel with growth (Figure 15.1a).