Introduction to product
formation kinetics
 Product formation kinetics is a branch of chemistry that studies the rates at
which chemical reactions occur.
 The goal of product formation kinetics is to understand how products are
formed, and how the rate of reaction can be affected by factors like
temperature, pressure, and the presence of catalysts.
 Product formation kinetics is important in a variety of industries, including
petrochemical refining, polymer production, and food processing.
 Understanding the rate of reaction can help optimize these processes and
make them more efficient.
 we assume that product formation is performed by the living cells, and
therefore live biomass concentration is used in the definition of the specific
product formation rate.
Product formation kinetics
categories
 Growth associated products – product is formed along with the
growth of the microbial cells and product concentration is almost
directly proportional to microbial growth rate. That is product
concentration increases with cell concentration.
 They are also called primary metabolites because they are essential
for the energy metabolism and biosynthesis of the cells.
 For example ethanol is a growth associated product that is produced
by yeast cells during fermentation
Cntd….
Non-growth associated products – product formation is nowhere
related with growth rate of microbial cells but it’s a function of cell
concentration and we can say that product formation and microbial
growth rate are almost inversely proportional to each other.
 Many biochemical processes fall into this category.
 For example penicillin is a non growth associated product that is
produced by some fungi after the exponential growth phase.
Penicillin is a secondary metabolite that acts as an antibiotic against
bacteria
Cntd…
• Mixed mode product – product formation is a combination of both
microbial cell concentration and microbial growth rate. Amino acids
and their products are some example
Graphs
Product formation kinetic
models
Type I:This is called the Leudeking-Piret model
Product is formed simultaneously with growth of cells. That is product
concentration increases with cell concentration.
rp =qp X ❑⇒α μg
1 dP
p
qp =
= Y μg
X dt
X
Where q p is the rate of product formation (h-1), µ g is the specific
growth rate and α and β is a coefficients
Cntd…
• Type II: This is guided by the Yuedilevee equation
• Product formation is unrelated to growth rate, but is a function of cell
concentration.
dP
•
= qp X = βX
dt
• Type III: product formation is a combination of growth rate and cell
concentration
• rp =qp X ⇒(α μg + β) X
• Note that if β is zero and α is YP/X, this case reduces to Type I. if α is zero,
it reduces to Type II.
Product inhibition
 Product inhibition is an important consideration in many
fermentations because this limits the final product concentration and
purity.
 product inhibition is the process by which the presence of a product
can slow down or stop the reaction that produces it.
 This can happen in a variety of ways, such as when a product binds
to an enzyme and blocks its active site, or when a product alters the
structure of the enzyme.
In product formation kinetics, the Arrhenius equation is also very
important in predicting how the rate of a reaction will change with
temperature
It states that the rate of reaction is proportional to the frequency of
collisions between reactant molecules and it is inversely proportional
to the activation energy of the reaction