Biochemical engineering note

1. Biochemical Engineering
Biochemical engineering
Biochemical engineering is the use of biological (natural or organic) materials, such as organisms, cells and
certain molecules, to develop products and processes. Industries that depend on biochemical engineering
include biotechnology, biofuels, pharmaceuticals, water purification and food.
What do biochemical engineers do?
Biochemical engineers use advanced technology and their knowledge of engineering, biology and chemistry
to create new products and manufacturing processes from biological materials. They often work with
scientists and other engineers in a lab to test interactions between materials to develop product ideas. They
then take those findings and work with manufacturers and technicians to develop the process for creating
and manufacturing a product, often on a large, commercial scale. Biochemical engineers often specialize in
certain areas, such as:
● Enzyme engineering: The production of chemicals and chemical reactions through enzymes
● Metabolic engineering: The production of metabolites through molecular genetics
● Tissue engineering: Treating disease or damaged tissue using living cells.
Biochemical engineers work with a variety of professionals, including scientists and chemists, other
engineers, manufacturing personnel, quality assurance staff and regulatory authorities.
What are Microbes/Microorganism
Microbes are also called microorganisms.The organisms which are so minute and vary in their size and
shapes, which cannot be seen by our naked eyes, can only be seen through the microscope are called
microorganisms. Therefore, they are also referred to as the microscopic organisms.
Microorganisms are beneficial in producing oxygen, decomposing organic material, providing nutrients for
plants, and maintaining human health, but some can be pathogenic and cause diseases in plants and
humans.
Industrial Importance of Microorganisms
In large-scale industrial processes, microbes are widely used to synthesize a number of products valuable
to human beings. There are numerous industrial products that are derived from microbes such as:
● Food additives.
● Alcoholic and non-alcoholic beverages.
● Biofuels, metabolites, and biofertilizers.
● Few Chemicals, Enzymes and other bioactive Molecules.
● Vaccines and other Antibiotics to kill or retard the growth of disease-causing microbes.
Role of microbes in industrial products:
● Beverages
Yeasts are the widely used microorganisms for the production of beverages like beer, brandy, rum, wine,
whiskey, etc.Yeasts are microorganisms of the kingdom Fungi.Saccharomyces cerevisiae or Brewer’s
Yeasts are used for fermenting fruit juices to produce ethanol.
● Organic acids
Microbes are also used for the industrial production of certain organic acids. Citric acid was the first
discovered organic acids from microbial fermentation of lemon

2. ● Enzymes
Enzymes are naturally occurring, biological catalysts that are mainly used to control certain biochemical
reactions in the living system. Enzymes have a wide range of applications in the production of both medical
and non-medical fields. Apart from the plants and animals, enzymes are also obtained from certain
microbes and are referred to as the microbial enzymes.
● Antibiotic Antibiotics
Antibiotic Antibiotics are chemical substances produced by certain microbes which function either by killing
or retarding the growth of harmful microbes without affecting the host cells. Penicillin was the first antibiotic
to be discovered from the fungus Penicillium notatum.
● Vitamins
Vitamins are organic compounds which are capable of performing many life-sustaining functions inside our
body. They are essential micronutrients which are required in small quantities for the body’s metabolism.
AAs our body cannot synthesize these vitamins, they need to be supplied through the diet. Apart from plants
and animals sources, microbes are also capable of synthesizing the vitamins. There are few groups of
microbes living in the digestive tracts of both humans and other animals which are collectively called the gut
microbiota. These microbes are involved in synthesizing vitamin K.
Enzymes vs. Inorganic Catalysts
The main difference between Enzymes and Inorganic Catalysts is that Enzymes are the globular proteins, whereas
Inorganic Catalysts are the small molecules or the mineral ions.

3. Enzymes: Catalysis and Kinetics
Catalysts are those substances that enhance the rate of a chemical reaction without themselves getting chemically
modified.There are multiple reactions that take place inside our body. These bio-reactions that occur in our body
during various life processes also require catalysts; the substances that act as biocatalysts for the reactions inside
our body are called enzymes.
General Properties of Enzymes:
1)A single molecule of the enzyme catalyst can transform up to a million molecules of the reactant per second.
Hence, enzyme catalysts are said to be highly efficient.
2) Enzymes are biological catalysts that speed up reactions with-out being consumed.
3) Enzymes are highly specific for their substrates. the same catalyst cannot be used in more than one reaction.
4) Enzymes display a high degree of reaction specificity which discourages wasteful byproducts.
5) Co-factors: organic coenzymes, and prosthetic groups (covalent) or inorganic (non-covalent)
6) In a metabolic pathway one reaction or one enzyme always represents the rate-limiting step, this determines the
rate for the entire pathway.
7)The effectiveness of a catalyst is maximum at its optimum temperature. The activity of the biochemical catalysts
declines at either side of the optimum temperature.
8)Biochemical catalysis is dependent upon the pH of the solution. A catalyst works best at an optimum pH
which ranges between 5-7 Ph values.
Mechanism of enzyme catalyst:
Mechanism of enzyme action and their selectivity can be best explained by the lock and key model.
Enzymes consist of a number of cavities which are present on the outer surface. These cavities possess groups
such as -COOH, -SH, etc. These centres are called the active centre of the biochemical particle.The substrate
forms a complex (intermediate) which then gives the product and the enzyme. The substrate that gets attached to
the enzyme has a specific structure and can only fit in a particular enzyme similar to that of a lock which has a
specific key. By providing a surface for the substrate, an enzyme brings down the activation energy of the reaction.
The substrate which has the opposite charge of the enzyme fits into the cavities just as a key fits into a lock. Due to
the existence of the active groups, the complex formed decomposes to give the products.

4. Hence this happens in two steps:
Step1: Combining of enzyme and the reactant
Step 2: Disintegration of the complex molecule to give the product

5. Potential energy diagram of enzyme catalyzed and uncatalyzed reaction
The diagram at left to represent an elementary
reaction that can take place with or without catalysis. The red curve shows the energy profile for the
uncatalyzed reaction. The activation energy for uncatalyzed conversion to products is much greater than
that for the catalyzed reaction (indigo curve).For both the uncatalyzed and the catalyzed reaction, the
potential energy change, ΔErxn, is the same. This means that while a catalyst does not alter the conditions
under which the reaction is at equilibrium.The reaction coordinate diagram shows that the energy of
activation for the reverse reaction is lowered by the catalyst as well.

6. Enzyme Kinetics
Michaelis-Menten Equation
Leonor Michaelis and Maud Leonora Menten, proposed the model known as Michaelis-Menten Kinetics to
account for enzymatic dynamics. The model serves to explain how an enzyme can cause kinetic rate
enhancement of a reaction and explains how reaction rates depend on the concentration of enzyme and
substrate.
The general reaction scheme of an enzyme-catalyzed reaction is as follows:
The enzyme (E) combines with the substrate(S), to form an enzyme-substrate(ES) complex, which
immediately breaks down to the Enzyme and the Product (P). Here k1, k2, k3, k4 are specific rate
constants.
Molar Concentration of [E] =Concentration of free (or) free (or) uncombined enzyme
● [ES]=Concentration of Enzyme-Substrate complex
● [Et]=Total enzyme concentration (the sum of the free and combined forms)
● [S]=Concentration of Substrate
● [P]=Concentration of Product
Accordingly, we can say that:
● v 1 = k 1 [E] [S]
● v 2 = k 2 [ES]
● v 3 = k 3 [ES]
One can distinguish between free enzyme (E) and attached to the enzyme substrate (S), so that the
total concentration of enzyme , [E T ], (which is constant throughout the reaction) is:
[E T ] = [E] + [ES]
As [E] = [ET] – [ES], it follows that:

7. v 1 = k 1 [S] [E T ] – k 1 [S] [ES]
This kinetic model adopts the steady-state hypothesis , according to which the concentration of the
enzyme-substrate complex is small and constant throughout the reaction
Therefore, the rate of formation of the enzyme-substrate complex (v 1 ) is equal to that of its dissociation
(v 2 + v 3 ):
v 1 = v 2 + v 3
Further, as [ES] is constant, the rate of formation of the products is constant:
v = v 3 = k 3 [ES] = constant .
As v 1 = v 2 + v 3 , we can say that:
k 1 [S] [E T ] – k 1 [S] [ES] = k 2 [ES] + k 3 [ES]
km=(k2+k3) / k1,where Km is Michaelis-Menten constant .
the maximum reaction rate (V max ): V max = k 3 [E T ]

8. Batch fermentation
Batch fermentation is what is described as a ‘closed system’, whereby the substrate and producing
microorganism are added to the system at time zero and are not removed until the fermentation is
complete.
1)Lag phase:Physicochemical equilibration between microorganism and the environment following
inoculation with very little growth.

9. 2) By the end of the lag phase cells have adapted
to the new conditions of growth.
3)
4)
FED BATCH FERMENTATION
In the conventional batch process just described, all of the substrate is added at the beginning of the
fermentation. An enhancement of the closed batch process is the fed batch fermentation. In the fed-batch
process, substrate is added in increments as the fermentation progresses. In the fed-batch method the
critical elements of the nutrient solution are added in small concentrations at the beginning of the
fermentation and these substances continue to be added in small doses during the production phase.
CONTINUOUS FERMENTATION

10. In continuous fermentation, an open system is set up. Sterile nutrient solution is added to the bioreactor
continuously and an equivalent amount of converted nutrient solution with microorganisms is
simultaneously taken out of the system. In the case of a homogeneously mixed bioreactor we refer to a
chemostat or a turbidistat. In the chemostat in the steady state, cell growth is controlled by adjusting the
concentration of one substrate. In the turbidistat, cell growth is kept constant by using turbidity to monitor
the biomass concentration and the rate of feed of nutrient solution is appropriately adjusted