bioprocess principles biotechnology -...
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BIOPROCESS PRINCIPLES
Biotechnology is a field of applied biology that involves the use of living organisms and
bioprocesses in Engineering, technology, medicine and other fields requiring bioproducts.
Biotechnology also utilizes these products for manufacturing purpose. Modern use of similar
terms includes genetic engineering as well as cell and tissue culture technologies. The concept
encompasses a wide range of procedures for modifying living organisms according to human
purposes — going back to domestication of animals, cultivation of plants, and "improvements"
to these through breeding programs that employ artificial selection and hybridization.
Bioprocess Engineering is a specialization of Boitechnology, Chemical engineering and
Agricultural Engineering. It deals with the design and development of equipment and processes
for the manufacturing of products such as food as feed, pharmaceuticals, chemicals
polymers and paper from biological materials.Bioprocees engineering is a combination of
mathematics, biology and industrial design, and consists of various spectrums like designing
of Fermentors, study of fermentors (mode of operations etc.).It also deals with studying various
biotechnological processes used in industries for large scale production of biological product for
optimization of yield in the end product and the quality of end product. Bio process engineering
may include the work of mechanical, electrical and industrial engineers to apply principles of
their disciplines to processes based on using living cells or sub component of such cells
Bio processing is an essential part of many food, chemical and pharmaceutical industries.
Bioprocess operations make use of microbial, animal and plant cells and components of cells
such as enzymes to manufacture new products and destroy harmful wastes. Use of
microorganisms to transform biological materials for production of fermented foods has its
origins in antiquity. Since then, bioprocesses have been developed for an enormous range of
commercial products, from relatively cheap materials such as industrial alcohol and organic
solvents, to expensive specialty chemicals such as antibiotics, therapeutic proteins and vaccines.
Industrially-useful enzymes and living cells such as bakers‘ and brewers‘ yeast are also
commercial products of bio processing. Our ability to harness the capabilities of cells and
enzymes has been closely related to advancements in microbiology, biochemistry and cell
physiology. Knowledge in these areas is expanding rapidly; tools of modern biotechnology such
as recombinant DNA, gene probes, cell fusion and tissue culture offer new opportunities to
develop novel products or improve Bio processing methods. Visions of sophisticated medicines,
cultured human tissues and organs, biochips for new-age computers, environmentally-compatible
pesticides and powerful pollution-degrading microbes herald a revolution in the role of biology
in industry. Biological systems can be complex and difficult to control; nevertheless, they obey
the laws of chemistry and physics and are therefore amenable to engineering analysis.
Engineering aspects are required in bioprocessing, including design and operation of
bioreactors, sterilisers and product-recovery equipment, development of systems for process
automation and control, and efficient and safe layout of fermentation factories.
Steps in Bioprocess Development
Manufacture of a new recombinant-DNA-derived product such as insulin, growth hormone or
interferon is shown above
Step-1-11 : Genetic Manipulation of the host organism where a gene from animal DNA is
cloned into Escherichia coil. Tools :Petri dishes, micropipettes, micro centrifuges, nano-or
microgram quantities of restriction enzymes, and electrophoresis gels for DNA and protein
fractionation.In terms of bioprocess development, parameters of major importance are stability
of the constructed strains and level of expression of the desired product.
Step-12 : After cloning, the growth and production characteristics of the cells must be measured
as a function of culture environment .Small-scale culture is mostly carried out using shake flasks
of 250-ml to 1-1itre capacity. Medium composition, pH, temperature and other environmental
conditions allowing optimal growth and productivity are determined. Calculated parameters such
as cell growth rate, specific productivity and product yield are used to describe performance of
the organism
Step-13 : Scale-up of the process
The first stage may be a 1- or 2-1itre bench-top bioreactor equipped with instruments for
measuring and adjusting temperature, pH, dissolved-oxygen concentration, stirrer speed and
other process variables.Cultures can be more closely monitored in bioreactors than in shake
flasks so better control over the process is possible. Information is collected about the oxygen
requirements of the cells, their shear sensitivity, foaming characteristics and other
parameters.The viability of the process as a commercial venture is of great interest; information
about activity of the cells is used in further calculations to determine economic feasibility
Step 14 :scaled up again to a pilot-scale bioreactor
Engineers trained in bio processing are normally involved in pilot-scale operations. A vessel of
capacity 100-1000 litres is built according to specifications determined from the bench-scale
prototype.Changing the size of the equipment seems relatively trivial; however, loss or variation
of performance often occurs. Even though the geometry of the reactor, method of aeration and
mixing, impeller design and other features may be similar in small and large fermenters, the
effect on activity of cells can be great. Loss of productivity following scale-up may or may not
be recovered; economic projections often need to be re-assessed as a result of pilot-scale
findings.
Step 15 : Design of the industrial-scale operation
This part of process development is clearly in the territory of bioprocess engineering. As well as
the reactor itself, all of the auxiliary service facilities must be designed and tested. These include
air supply and sterilisation equipment, steam generator and supply lines, medium preparation and
sterilisation facilities, cooling-water supply and process-control network. Particular attention is
required to ensure the fermentation can be carried out aseptically, design of the process must also
reflect containment and safety requirements
Step :16 : Product Recovery (downstream processing)
After leaving the fermenter, raw broth is treated in a series of steps to produce the final product.
Product recovery is often difficult and expensive; for some recombinant - DNA-derived
products, purification accounts for 80-90% of the total processing cost.Downstream processing
depend on the nature of the product and the broth; physical, chemical or biological methods may
be employed.Commercial procedures include filtration, centrifugation and flotation for
separation of cells from the liquid, mechanical disruption of the cells product is intracellular,
solvent extraction, chromatography, membrane filtration, adsorption, crystallisation and
drying.Scientists trained in chemistry, biochemistry, chemical engineering and industrial
chemistry play important roles in designing product recovery and purification "systems.
Step 17 : Packing and Marketing
For new pharmaceuticals such as recombinant human growth hormone or insulin, medical and
clinical trials are required to test the efficacy of the product. Animals are used first, then humans.
Only after these trials are carried out and the safety of the product established can it be released
for general health-care application. Other tests are required for food products. Manufacturing
standards must be met; this is particularly the case for recombinant products where a greater
number of safety and precautionary measures is required.
Bioprocesses treat raw materials and generate useful products. Individual operations or steps
within the process that change or separate components are called unit operations. Although the
specific objectives of bioprocesses vary from factory to factory, each processing scheme can be
viewed as a series of component operations which appear again and again in different systems.
For example, most bioprocesses involve one or more of the following unit operations:
centrifugation, chromatography, cooling, crystallisation, dialysis, distillation, drying,
evaporation, filtration, heating, humidification, membrane separation, milling, mixing,
precipitation, solids handling, solvent extraction. In a typical fermentation process, raw materials
are altered most significantly by reactions occurring in the fermenter. However physical changes
before and after fermentation are also important to prepare the substrates for reaction and to
extract and purify the desired product from the culture broth .Fermentation broths are complex
mixtures of components containing products in dilute solution. In bioprocessing, any treatment
of the culture broth after fermentation is known as downstream processing. The purpose of
downstream processing is to concentrate and purify the product for sale; in most cases this
requires only physical modification.
Recovery scheme will be different, downstream processing follows a general sequence of
steps.
Cell removal. A common first step in product recovery is removal of cells from the fermentation
liquor. This is necessary if the biomass itself is the desired product. e.g. bakers' yeast, or if the
product is contained within the cells. Removal of cells can also assist recovery of product from
the liquid phase. Filtration and centrifugation are typical unit operations for cell removal.
Primary isolation. A wide variety of techniques is available for primary isolation of
fermentation products from cells or cell-free broth. The method used'depends on the physical and
chemical properties of the product and surrounding material. Typically, processes for primary
isolation treat large volumes of material and are relatively non-selective; however significant
increases in product quality and concentration can be accomplished. Unit operations such as
adsorption, liquid extraction and precipitation are used for primary isolation
Purification. Processes for purification are highly selective and separate the product from
impurities with similar properties. Typical unit operations are chromatography, ultrafiltration and
fractional precipitation.
Final isolation. The final purity required depends on the product application. Crystallisation,
followed by centrifugation or filtration and drying, are typical operations used for high-quality
products such as pharmaceuticals.
Process Flow Diagrams
Because of the complexity of large-scale manufacturing processes, communicating information
about these systems requires special methods. Flow diagrams or flow sheets are simplified
pictorial representations of processes and are used to present relevant process information and
data. Flow sheets vary in complexity from simple block diagrams to highly complex schematic
drawings showing main and auxiliary process equipment such as pipes, valves, pumps and by-
pass loops.
Production of the antibiotic, bacitracin
Discovery of Penicillin
Penicillin was discovered by chance, after Alexander Fleming accidentally left a dish of
staphylococcus bacteria uncovered for a few days. He returned to find the dish dotted with
bacterial growth, apart from one area where a patch of mould (Penicillin notatum) was growing.
The mould produced a substance, named penicillin by Fleming, which inhibited bacterial growth
and was later found to be effective against a wide range of harmful bacteria. However, it was not
until World War II that penicillin, the first antibiotic, was finally isolated by Howard Florey and
Ernst Chain. Fleming, Florey and Chain received a Nobel prize in 1945, for their discovery
which revolutionised medicine and led to the development of life saving antibiotics.
Manufacture of Penicillin
Though the precise and exact compositions of the penicillin-production media really employed in
any industry are more or less impossible to quote and determine, by virtue of the fact that such
information(s) are regarded to be the 'trade secrets' or patented by the actual users. Nevertheless,
a large segment of these commonly used media invariably comprises of such ingredients as: corn
steepliquor solids, lactose, glucose, calcium carbonate, potassium di hydrogen phosphate
[KH2PO4 ], edibleoil, and a penicillin precursor. Jackson (1958) promulgated a very useful and
typical medium having essentially the following composition
(1) The pH after sterilization is carefully maintained between 5.5 to 6.0.
(2) Higher lactose content ranging between 4 to 5% is desired with vigorously increased aeration
and agitation environments maintained within the fermentor (i.e., bioreactor).
(3) The 'production media' contains both 'lactose' and 'precursor' which are not included in the
inoculums media
Penicillin Production
1.The completed penicillin fermentation culture is subjected to filtration by the help of
heavy duty rotary vacuum filter to get rid to the mycelium plus other unwanted solid residues.
2. The pH of the clear filtered fermented broth is carefully brought down between 2 to 2.5 by the
addition of a calculated amount of either phosphoric or sulphuric acid so as to convert the
resulting penicillin to its anionic form.
3. The resulting fermented broth (pH 2-2.5) is extracted immediately by using countercurrent
solvent extractor, with an appropriate organic solvent e.g., amyl acetate, butylacetate, or methyl
isobutyl ketone.
4. Penicillin, thus obtained, is back extracted into aqueous medium from the corresponding
organic solvent by the careful addition of requiste quantum of KOH or Na0H to give rise to the
formation of the corresponding potassium or sodium salt of the penicillin.
5. The resulting aqueous solution, containing the respective salt of penicillin, is again acidified
and re-extracted with the organic solvent methyl isobutyl ketone
6. The resulting solvent extract is finally subjected to a meticulous back-extraction with aqueous
NaOH preferably, a number of times till extraction of penicillin is completed; and from this
combine of aqueous extractions different established procedures are adopted to afford the
penicillin to crystallize out either as sodium or potassium penicillin
7. The crystalline penicillin thus obtained is washed, dried under vacuum, and the final product
must conform to the requirements/specifications
Ethanol Production
Ethanol has been made since ancient times by the fermentation of sugars. All beverage ethanol
and more than half of industrial ethanol is still made by this process. Simple sugars are the raw
material. Zymase, an enzyme from yeast, changes the simple sugars into ethanol and carbon
dioxide. The fermentation reaction, represented by the simple equation
C6H12O6 2 CH3CH2OH + 2 CO2
It is actually very complex, and impure cultures of yeast produce varying amounts of other
substances, including glycerine and various organic acids. In the production of beverages, such
as whiskey and brandy, the impurities supply the flavor. Starches from potatoes, corn, wheat,
and other plants can also be used in the production of ethanol by fermentation. However, the
starches must first be broken down into simple sugars. An enzyme released by germinating
barley, diastase, converts starches into sugars.Thus, the germination of barley, called malting, is
the first step in brewing beer from starchy plants, such as corn and wheat.
The ethanol produced by fermentation ranges in concentration from a few percent up to about 14
percent. Above about 14 percent, ethanol destroys the zymase enzyme and fermentation stops.
Ethanol is normally concentrated by distillation of aqueous solutions, but the composition of the
vapor from aqueous ethanol is 96 percent ethanol and 4 percent water. Therefore, pure ethanol
cannot be obtained by distillation. Commercial ethanol contains 95 percent by volume of ethanol
and 5 percent of water. Dehydrating agents can be used to remove the remaining water and
produce absolute ethanol.
Manufacture of Lactic Acid
Lactic acid has been first introduced to us as early as 1780 as a sour component of milk. Ever
since we have found its applications in food, pharmaceutical, cosmetic industries etc.
Lactic acid bacteria compose a group of bacteria that degrade carbohydrate with the production
of lactic acid. Examples of genera that contain lactic acid bacteria
include Streptococcus, Lactobacillus, Lactococcus, and Leuconostoc
Enzyme Production
Sources of Industrial Enzymes can be
a. Plant
b. Animals
c. Microorganism
Selection of industrial enzymes from any of these sources depends on the following factors:
a. specificity
b. pH
c. Thermo stability
d. activation or inhibition
e. availability and cost
Enzymes and their producer microorganisms
Most industrial enzymes are products of batch processes and few are currently pro-duced via
continuous fermentation. The fermenters for bulk enzyme production are up to 100m3capacity,
but fine enzymes may be produced on smaller scales of a few hundred litres or less. Most
fermenters are stirred tank reactors that are operated under aseptic conditions and use low cost
undefined complex media.
As in the development of any fermentation process, enzyme production processes includes the
following steps
• search for a suitable producer organism.
• screening of microorganism and selection to determine enzyme properties, such as opti-
mum pH and heat resistance, and examination of the ability to secrete the target enzyme.
• The fermentation system and ferementation media to be determined. Conditions for
maximum production of the enzyme per unit of biomass, using inexpensive car-bon and
nitrogen feedstocks, must be identified.
• Downstream processing involves separation,. Purification, stabilization and preservation
Enzyme stability has to be determined as it can influence the timing, and operations used
in, downstream processing.
• The level of purification applied varies considerably depend-ing on whether the enzyme
is intracellular or extracellu-lar, and on its end use.
Generalised manufacture of enzymes
Processing of Biological Material
Filtration
In filtration, solid particles are separated
a filter medium or filter cloth which retains the particles. Solids are deposited on the filter
the deposit or filter cake increases in depth, pose a
performed using either vacuum or positive
across the filter to separate fluid from the solids is called the filtration
Fermentation broths can be difficult to filter because of the small size and gelatinous nature of
the cells and the viscous non-Newtonian behaviour of the broth. Most microbial filter cakes are
compressible, i.e. the porosity of the cake declines as
This can be a major problem causing reduced filtration rates and greater loss of p
Processing of Biological Material
In filtration, solid particles are separated from a fluid-solid mixture by forcing the fluid through
filter medium or filter cloth which retains the particles. Solids are deposited on the filter
filter cake increases in depth, pose a resistance to further filtration.Filtration can be
performed using either vacuum or positive-pressure equipment. The pressure difference exerted
across the filter to separate fluid from the solids is called the filtration
Fermentation broths can be difficult to filter because of the small size and gelatinous nature of
Newtonian behaviour of the broth. Most microbial filter cakes are
compressible, i.e. the porosity of the cake declines as pressure drop across the filter increases.
This can be a major problem causing reduced filtration rates and greater loss of p
mixture by forcing the fluid through
filter medium or filter cloth which retains the particles. Solids are deposited on the filter and, as
resistance to further filtration.Filtration can be
e equipment. The pressure difference exerted
across the filter to separate fluid from the solids is called the filtration pressure drop.
Fermentation broths can be difficult to filter because of the small size and gelatinous nature of
Newtonian behaviour of the broth. Most microbial filter cakes are
pressure drop across the filter increases.
This can be a major problem causing reduced filtration rates and greater loss of product.
Filter Aids:
Filter aids such as diatomaceous earth have found widespread use in the fermentation industry to
improve the efficiency offiltration.Filter aids are applied in two ways. As shown in Figure, filter
aid can be used as a pre-coat on the filter medium to prevent blockage or 'blinding' of the filter
by solids which would otherwise wedge themselves into the pores of the cloth. Filter aid can also
be added to the fermentation broth to increase the porosity of the cake as it forms.
Centrifugation
Centrifugation is used to separate materials of different density when a force greater than gravity
is desired. In bioprocessing, centrifugation is used to remove cells from fermentation broth, to
eliminate cell debris, to collect precipitates, and to prepare fermentation media such as in
clarification of molasses or production of wort for brewing.Centrifugation is most effective when
the particles to be separated are large, the liquid viscosity is low, and the density difference
between particles and fluid is great. It is also assisted by large centrifuge radius and high
rotational speed.In centrifugation of biological solids such as cells, the particles are very small,
the viscosity of the medium can be relatively high, and the particle density is very similar to the
suspending fluid.
Disc-stack bowl centrifuge
Cell Disruption
For products such as enzymes and recombinant proteins which remain in the biomass, cell
disruption must be carried out to release the desired material.Variety of methods is available to
disrupt cells. Mechanical options include grinding with abrasives, high-speed agitation, high-
pressure pumping and ultrasound. Non-mechanical methods such as osmotic shock, freezing and
thawing, enzymatic digestion of cell walls, and treatment with solvents and detergents can also
be applied.
High-pressure pump incorporates an adjustable valve with restricted orifice through which cells
are forced at pressures up to 550 atm. The homogeniser is of general applicability for cell
disruption, although the homogenising valve can become blocked when used with highly
filamentous organisms.
Aqueous Two-Phase Liquid Extraction
In liquid extraction of fermentation products, components dissolved in liquid are recovered by
transfer into an appropriate solvent. Extraction of penicillin from aqueous broth using solvents
such as butyl acetate, amyl acetate or methyl isobutyl ketone, and isolation of erythromycin
using pentyl or amyl acetate are examples.Solvent extraction techniques are also applied for
recovery of steroids, purification of vitamin B12 from microbial sources, and isolation of
alkaloids such as morphine and codeine from raw plant material.
Techniques are being developed for aqueous two-phase extraction of these molecules. Aqueous
solvents which form two distinct phases provide favourable conditions for separation of proteins,
cell fragments and organelles with protection of their biological activity.
Chromatography
Chromatography is a separation procedure for resolving mixtures and isolating components. The
basis of chromatography is differential migration, i.e. the selective retardation of solute
molecules during passage through a bed of resin particles.
As solvent flows through the column, the solutes travel at different speeds depending on their
relative affinities for the resin particles. As a result, they will be separated and appear for
collection at the end of the column at different times. The pattern of solute peaks emerging from
a chromatography column is called a chromatogram.The fluid carrying solutes through the
column or used for elution is known as the mobile phase; the material which stays inside the
column and effects the separation is called the stationary phase.Chromatography is a high-
resolution technique and therefore suitable for recovery of high-purity therapeutics and
pharmaceuticals. Chromatographic methods available for purification of proteins, peptides,
amino acids, nucleic acids, alkaloids, vitamins, steroids and many other biological materials
include adsorption chromatography, partition chromatography, ion-exchange chromatography,
gel chromatography and affinity chromatography. These methods differ in the principal
mechanism by which molecules are retarded in the chromatography column.
Distillation
Distillation is simply defined as a process in which a liquid or vapor mixture of two or more
substances is separated into its component fractions of desired purity, by the application and
removal of heat.
Evaporation
Evaporation is the removal of a po
evaporates and solids do not evaporate. By evaporation the solid concentration in the solution is
increased.
Tie substance balance.
Any material which does not get altered in a process is called
substance balance the quantities of the streams are evaluated.
Crystallization
In process industries products are produced with impurities in the reactors. To get pure products
different unit operations such as distilla
Crystallization is carried out when a solid product is to be recovered from its solution with other
component. This is done by super saturating the solution by one or more of the three methods
namely cooling, evaporation and adiabatic cooling. If the solubility of the solute increases to
larger extent with increase in temperature (strong function of temperature) a saturated solution
becomes super saturated by simply cooling and temperature reduction.To incr
of crystallization, adiabatic cooling is normally carried out (evaporation and cooling
simultaneously carried out with out the addition of heat). Some times a solid has to be removed
from solid mixture. The purification of the mixture (se
Evaporation is the removal of a portion of solvent by boiling the solution. Only liquid portion
evaporates and solids do not evaporate. By evaporation the solid concentration in the solution is
Any material which does not get altered in a process is called a tie substance. By writing a tie
substance balance the quantities of the streams are evaluated.
In process industries products are produced with impurities in the reactors. To get pure products
different unit operations such as distillation, evaporation, crystallization etc. are used.
Crystallization is carried out when a solid product is to be recovered from its solution with other
component. This is done by super saturating the solution by one or more of the three methods
g, evaporation and adiabatic cooling. If the solubility of the solute increases to
larger extent with increase in temperature (strong function of temperature) a saturated solution
becomes super saturated by simply cooling and temperature reduction.To increase the capacity
of crystallization, adiabatic cooling is normally carried out (evaporation and cooling
simultaneously carried out with out the addition of heat). Some times a solid has to be removed
from solid mixture. The purification of the mixture (separation of one component) is carried out
rtion of solvent by boiling the solution. Only liquid portion
evaporates and solids do not evaporate. By evaporation the solid concentration in the solution is
a tie substance. By writing a tie
In process industries products are produced with impurities in the reactors. To get pure products
tion, evaporation, crystallization etc. are used.
Crystallization is carried out when a solid product is to be recovered from its solution with other
component. This is done by super saturating the solution by one or more of the three methods
g, evaporation and adiabatic cooling. If the solubility of the solute increases to
larger extent with increase in temperature (strong function of temperature) a saturated solution
ease the capacity
of crystallization, adiabatic cooling is normally carried out (evaporation and cooling
simultaneously carried out with out the addition of heat). Some times a solid has to be removed
paration of one component) is carried out
by treating the solid mixture with a suitable solvent so as to dissolve only the desired component
and then crystallizing it. The solubility of solute plays an important role in the crystallization
operation
Drying
Drying refers to an operation in which the moisture of a substance is removed by thermal means
the removal of relatively small amount of water or other liquids from the solid material. Drying
is one of the oldest methods of preserving food. Primitive societies practiced the drying of meat
and fish in the sun long before recorded history.