2. WHAT IS FERMENTATION
?■ Fermentation is an anaerobic (non-oxygen-requiring) pathway for breaking down glucose,
one that's performed by many types of organisms and cells using different types of
enzymes.
■ In fermentation, the only energy extraction pathway is glycolysis, with one or two extra
reactions tacked on at the end.
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TYPES OF FERMENTATION
LACTIC ACID FERMENTATION
ALCOHOL FERMENTATION
6. GENERAL ACPECTS OF
FERMENTATION PROCESS
■ (a)The concentrations of starting materials (substrates) and products in the reaction
mixture are frequently low; both the substrates and the products may inhibit the
process. Product formation depend on the nutritional needs of the cell (salts, oxygen)
and on the maintenance of optimum biological conditions (temperature,
concentration of reactants, and pH) with in narrow limits.
■ (b) Certain substances inhibitors effectors, precursors, metabolic products influence
the rate and the mechanism of the reactions and intracellular regulation.
■ (c) Microorganisms can metabolize unconventional or even contaminated raw
materials (cellulose, molasses, mineral oil, starch, ores, wastewater, exhaust air,
biogenic waste), a process which is frequently carried out in highly viscous, non-
Newtonian media.
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7. ■ d) In contrast to isolated enzymes or chemical catalysts, microorganisms adapt the
structure and activity of their enzymes to the process conditions, whereby selectivity
and productivity can change. Mutations of the microorganisms can occur under sub
optimal biological conditions.
■ (e) Microorganisms are frequently sensitive to strong shear stress and to thermal and
chemical influences.
■ (f) Reactions generally occur in gas-liquid -solid systems, the liquid phase usually being
aqueous.
■ (g)The microbial mass can increase as biochemical conversion progresses. Effects
such as growth on the walls, flocculation, or autolysis of microorganisms can occur
during the reaction.
■ (h) Continuous bioreactors often exhibit complicated dynamic behavior. Due to above
mentioned demands made by biological systems on their environment, there is no
universal bioreactor.
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8. TYPES OF FERMENTERS
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STIRREDTANK FERMENTER (BATCH FERMENTER)
The Stirred tank reactor is provided with a baffle and a
rotating stirrer is attached either at the top or at the bottom
of the bioreactor.
The typical decision variables are: type, size, location and the
number of impellers; sparger size and location.
ADVANTAGE :Many industries still prefers stirred tanks
because in case of contamination or any other substandard
product formation the loss is minimal. Easy and low cost of
operation.
DISADVANTAGE :The batch stirred tanks generally suffer due
to their low volumetric productivity.The fed batch mode
adopted in the recent years eliminates this limitation.
9. AIR-LIFT FERMENTER(BATCH FERMENTER) :
■ Airlift fermenter (ALF) is generally classified as pneumatic
reactors without any mechanical stirring arrangements for
mixing.
■ The turbulence caused by the fluid flow ensures adequate
mixing of the liquid.The draft tube is provided in the
central section of the reactor.The introduction of the fluid
(air/liquid) causes upward motion and results in circulatory
flow in the entire reactor.
■ It is ideally suited for aerobic cultures since oxygen mass
transfer coefficient are quite high in comparison to stirred
tank reactors.
■ ADVANTAGE:The advantages of Airlift reactors are the
elimination of attrition effects generally encountered in
mechanical agitated reactors
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10. PACKED BED FERMENTER
■ The use of packed bed reactors gained importance after the
potential of whole cell immobilization technique has been
demonstrated.
■ The immobilized biocatalyst is packed in the column and
fed with nutrients either from top or from bottom.
■ ADVANTAGE : Packed beds arc generally used where
substrate inhibition governs the rate of reaction.
■ DISADVANTAGE :Though packed beds belong to the class
of plug flow reactors in which backmixing is absent in many
of the packed beds slight amount of backmixing occurs
which changes the characteristics of fermentation
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11. BUBBLE COLUMN FERMENTER (CONTINOUS FERMENTER)
Bubble column fermenter is a simplest type of tower fermenter
consisting of a tube which is air sparged at the base.
It is an elongated non-mechanically stirred fermenter with an
aspect ratio of 6:1.
This type of fermenter was used for citric acid production.
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12. DESIGN OF A BATCH STIRRED FERMENTER FOR
ETHANOL PRODUCTION
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13. PRACTICAL PART
■ Ethanol production with cells Saccharomyces cerevisiae under anaerobic conditions is
a typical example of cell cultivation with a primary metabolic product generation
directly connected with the biomass growth. From this follows that only one overall
equation is necessary for a description of the cell stoichiometry.The key (limiting)
substrate is glucose.
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14. PHYSICAL REQUIREMENTS OF S. CEREVISIAE
■ TEMPERATURE : 30-37 degree Celsius
■ ph : 5-6.5
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. NUTRITIONAL REQUIREMENTS OF S. CEREVISIAE
KH2PO4-0.1%,
(NH4)2SO4-0.5% and
MgSO4.7H2O -0.05%
15. Microbial kinetics
■ Unstructured model is assumed to describe the microbial kinetics of alcohol
fermentation yeasts Saccharomyces cerevisiae that provides a nice example of
products inhibition with specific-growth function of the type [2]
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• Where µmax is the maximum specific biomass growth rate, ks is the saturation
constant of glucose, cs is the concentration of glucose, cp is the concentration of
biomass, kp is the inhibition parameter.
• Values of kinetics parameters for the description of microbial kinetics and next
applied in mathematical modeling were evaluated on the basis of literature
information [1]
16. Mixing and power consumption
■ The pumping capacity,VP, is that volume of liquid that gets expelled from the impeller per
unit time (m3 /s) and is defined by
■ The mixing time, tm, is the time needed to obtain a certain value of the degree of mixing
(homogeneity)
■ VL is liquid working volume
■ The power consumption, P, for unaerated conditions for multiple impellers put on the same
shaft is expressed through the following relation [1]:
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Where Nf is the flow number that depends on impeller type and on the medium viscosity (Nf =
0,72 for Rushton turbine and low viscosity medium), ds is the stirrer diameter and N is the stirrer
rate [1]
17. REFERENCES
■ 1] Nielsen J.,Villadsen J., Liden G.."BioreactionPrinciples", second edition, Kluwer
Academic, NewYork; 2002
■ 2] Procedia Engineering 149 ( 2016 ) 389 –Published by Elsevier Ltd. International
Conference on Manufacturing Engineering and Materials, ICMEM 2016, 6-10 June
2016, NovýSmokovec, Slovakia Design of a batch stirred fermenter for ethanol
production Mohammad EmalQazizadaa
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