2. Modeling of biochemical systems
When the stability of systems is analyzed, a mathematical
model correctly reproducing the dynamic behavior of the process
is required. A suitable design of the processes starts from a good
knowledge of the system. For this reason, it is important to know
the models used to describe the dynamic behavior of biochemical
systems. According to the purpose of study, specific models can be
applied.
In general, a bioreactor can be modeled by a differential equations
system. If uniformity (perfect mixture) inside the bioreactor
is assumed, solely variations with regard to the time occur, and
the system can be described by a set of first order ordinary differential
equations. These equations result from material balances
formulation for components considered in the system. Other mathematical
expressions are established to define the bio-reaction
kinetics.
The microbial growth, perhaps, is the process that has generated
more difficulty for its modeling due to the multiple interactions
between cells and environment, and to the great amount of
biochemical reactions affecting the cellular activity. Several conceptual
and mathematical models have been formulated to explain
and to describe the behavior of different biological systems. Several
authors classify the models depending on the consideration
assumed about cells structure and cellular population distribution.
The most general classification includes unstructured, structured
and segregated models. These models are explained below.