FERMENTATION INDUSTRY OF
ALCOHOL
LECTURE-6
COURSE CODE: CHM-3112/512
COURSE TITLE: APPLIED CHEMISTRY-II
COURSE INCHARGE: DR. FARZANA NAZ
INTRODUCTION TO THE TOPIC
Fermentation naturally occurs in yeast and some bacteria. Alcohol is commercially
produced by using yeast. During fermentation, sugar is anaerobically converted
into ethanol, water, and carbon dioxide. Louis Pasteur first worked on the living
identity of yeast and its capability to convert fruit sugar into alcohol (alcoholic
fermentation). He also worked lactic acid production by bacteria (lactic acid
fermentation). In today’s time the science that deals with fermentation is called
zymology.
CONTENTS OF THE LECTURE
 Introduction to Fermentation Industry
 Uses
 Raw Material
 Manufacturing Process
 Batch and Continuous Process
OBJECTIVES AND LEARNING GOALS
 By the end of this lecture you should be familiar with:
 Fermentation Industry
 Raw materials and utilizing of the byproducts
 Manufacturing process of Alcohols by using Batch and
Continuous Process
BUILDING ON (Prerequisites)
 Introduction of Sugar Industry
 Raw Material
 Byproducts
 Manufacturing Process
 Raw & Refined Sugar
 Factors Affecting Sugar Storage
INTRODUCTION
 Fermentation naturally occurs in yeast and some bacteria.
 Alcohol is commercially produced by using yeast. During fermentation, sugar is
anaerobically converted into ethanol, water, and carbon dioxide.
 Two types of fermentations are known in first sugars from fruit get fermented
which is known as alcoholic fermentation. Whereas, production of lactic acid by
bacteria is called lactic acid fermentation.
 In today’s time the science that deals with fermentation is called zymology.
Chemically alcoholic fermentation is divided into two phases:
 In the first phase the glucose (sugar) is converted into pyruvate by
glycolysis.
 The second phase involves the conversion of pyruvate in alcohol.
So basically, the second phase is the fermenting step of the reaction.
ALCOHOLIC FERMENTATION
 Ethanol is obtained by the fermentation process where the sugar content in fruit
juices and honey of crops are transformed into alcohol using yeast.
 Fermentation is mostly feasible for countries where sugar cane is produced at a
large extent.
 Ethanol production can largely be increased if fermentation process is updated.
 For making beers and lagers, barley is frequently used and for making wines the
sugar source is crushed grapes.
 To increase the alcoholic contents of the beverage, distillation is done because yeast
cannot tolerate high levels of alcohol and die.
 In the process of distillation, fermented solution is heated to vaporize ethanol at the
temperature around 78.5 ˚C and after that ethanol vapors are collected and
condensed in another flask to get concentrated ethanol.
Uses
 Alcoholic fermentation produces all different types of alcoholic beverages, where
the type of beverage depends on the source of sugar and final alcohol content.
 The alcoholic beverages that are produced by distillation are vodka, rum, and other
spirits.
 Alcoholic fermentation has another application in the bread making industry,
where yeast is mixed with dough for the fermentation process. The only difference
here is unlike beverages, the carbon dioxide produced during reaction makes the
dough rise and ethanol evaporates from it.
 Ethanol is mostly used as fuel and has become an alternative of renewable energy
source now-a-days.
 Ethanol is an eco-friendly alternative to petroleum-based fuel as it has fewer
greenhouse gas emissions.
 The production of ethanol is growing day by day at a great extent for its versatile
application and demand.
 As the supply and price of oil and gas worldwide has become a major problem,
ethanol is taking place as an alternative. Worldwide ethanol production as fuel
reached 32.35 billion gallons in 2012.
Raw Material
SUGAR BEET
Mostly preferred
15% sugar, 82% water, small amount of
starch
Juice is extracted by crushing
A ton yield 20 – 25 gallons of alcohol
Enzymes improve the alcohol yield
SUGAR CORN WASTE
7 – 15% sugar
Sugar is extracted as same as sorghum
8 – 18% gallons of alcohol per ton
Back slopping in the range of 20-25%
Acidification is necessary
Sugar beet sugar corn
PRODUCTION PROCESS OF ALCOHOL
Production process of alcohol is carried out in 3 stages
1. Inoculum
2. Proper fermentation
3. Recovery
Preparation of Inoculum
 A small amount of material containing bacteria, viruses, or other microorganisms
that is used to start a culture is called inoculum.
 After selection of desired organism in its pure form the inoculum is prepared
under aseptic condition.
 For this condition organism is first cultured in flask to increase the size of the
inoculum when increases the size of the inoculum which can then be used for
inoculation.
Manufacturing Process
Depending on the extraction process of molasses from different sources,
compositions can be varied.
Reaction involved
Two reactions involve with this process, one is for fermentation and another is for
conversion of fructose to ethanol.
Catalyst of fermentation reaction is invertase enzyme from yeast and the Catalyst of
ethanol conversion reaction is zymase.
 Previously Batch fermentation was used but now Continuous fermentation is used
as it increases the alcohol production by 10-12 fold as compare to batch
fermentation.
 Large fermenter of size 125,000 gallon are used .
 Initially aeration is required for good growth of micro organism. Later anaerobic
conditions are created by withdrawal of oxygen .
 It take 2-3 days for the fermentation to complete.
 Fermentation of sugar by Saccharomyces cervisiae is carried out for production of
ethanol in a batch experiment .
 When the temperature was increased to 45°C, the system still showed high cell
growth and ethanol production rates, while it was inhibited at 50°C.
 The maximum specific growth rate and the maximum specific ethanol
production rate were observed between 30-45°C.
 pH 4.0-5.0 was the optimal range for the ethanol production process.
 The highest specific ethanol production rate for all the batch experiments
was achieved at pH 5.0.
 Formation of acetic acid was increased when the pH was below 4.0, while
butyric acid was produced when the pH was higher than 5.0
BATCH FERMENTATION
 In Batch fermentation bacteria are inoculated into the bioreactor .
 Then under optimal condition (temp, pH etc) the bacteria go through all
the growth phases (LAG, exponential and stationary).
 It may be necessary to add acid or alkali to maintain pH and antifoaming
agents to minimize foam under optimal condition for growth.
GROWTH PHASES
LAG PHASE
 This is the initial period just after the inoculation
 During lag phase microorganisms adapt to the new environment (available
nutrient ,pH etc)
 No increase in cell number, although cellular weight may slightly increase.
ACCELERATION PHASE
This is the transient period during which cell start growing slowly. It connect lag
phase to log phase.
LOG PHASE
 Most active growth of micro-organism and multiplication occur during log phase.
 Number of cells and rate of population increases doubles with each consecutive time
period.
 Growth rate of microbes in log phase is dependent on substrate(nutrient supply)
STATTIONARY PHASE
 Depletion (Lessening) of nutrients and accumulation of metabolic end product .
Microbial growth may either completely slow down or completely stop. The
number of cells produced is limited by growth factor and as a result the rate of
cell growth matches the rate of cell death.
DEATH PHASE
Cells die at an exponential rate
At last fermentation is stopped and
product is collected.
Then after cleaning and sterilization
of fermenter, It is ready for another
batch.
ADVANTAGES
VERSATILE- can be used for different reaction everyday.
SAFE- can be properly sterilized. Little risk of infection or strain mutation.
Complete conversion of substrate is possible.
DISADVANTAGS
 High labor cost: Skilled labor is required.
 High proportion of Down time between batches
 Product Variability – The quality and quantity (to some extent ) may vary from
one batch to other batch.
 Safety Problem- when cleaning, filling and emptying.
CONTINIOUS FERMENTATION
In, continuous fermentation fresh medium flows into the fermenter continuously,
and a part of the medium is withdrawn from the fermenter at the same flow rate of
the inlet flow.(so that working volume remain constant). Chemostat bioreactor are
frequently used in industrial manufacturing of ethanol. BY changing the rate at
which the medium is added to the bioreactor the specific growth rate of the microorganism can be easily controlled.
ADVANTAGES
 Low labor cost
 Growth rate is higher as nutrients are continuously added to the reactor.
 More efficient as the fermenter operates continuously.(No down time )
DISADVANTAGE
• If contamination occur huge volume of product may be lost.
Step # 01: Fermentation
 Dissolved sugar from ground up molasses is diluted by mixing water with it.
 Sulfuric acid is added with diluted sugar to prevent bacterial contamination.
 Yeast is added with this before feeding to fermenter.
 Yeast provides invertase and zymase enzymes. Only sucrose of this diluted
sugar is degraded by invertase enzyme, this process is referred to as
hydrolysis.
 Glucose and fructose are obtained by hydrolysis of sucrose. The conversion of
sucrose in the fermenter was defined in 90 %.
 Glucose and Fructose is converted into ethanol and carbon-di-oxide, where
conversion rate is defined as 95%. Catalyst of this reaction is zymase.
 CO2 gas leaving the fermenter carries away some ethanol with it.
Step # 02: CO2 washing
 This gaseous stream is sent to CO2 Washer which is an absorption column. Here
ethanol is absorbed by wash water.
 The gaseous stream leaving the absorber contains negligible amount of ethanol
and this stream is vented in atmosphere.
 The liquid stream is recycled to the fermenter.
Step # 03: Ethanol Distillation (RECOVERY)
 The liquid stream leaving the fermenter is a very dilute ethanol solution which also
contains some sucrose, glucose, fructose and sulfuric acid.
 This stream is sent to the Concentration Tower which is a stripping column.
 Superheated steam at atmospheric pressure is used as the stripping gas (Stripping is
a physical separation process by which one or more components are removed from a
liquid stream by a vapor stream.)
 The Liquid Stream from the bottom of this tower contains water with trace of sucrose,
glucose fructose and sulfuric acid.
 A side stream is drawn from the 6th theoretical stage of this tower, which is sent to
Rectifier.
 The gaseous stream emerging from top of the tower is sent to Light Purification
Tower. Light Purification Tower used in this process is modeled as refluxed
absorber (i.e., non-heating fractional distillation by ultrasonic irradiation). Partial
condenser is used in this tower.
 Ethanol content of the gas stream leaving the condenser of this tower is low and its
flow rate is also kept very low.
 By this stream rest of the CO2 gas is vented to atmosphere, which was not removed
by the CO2 Washer.
 The liquid stream leaving the bottom of this tower is a dilute ethanol solution with
no other component. This is also fed to the Rectifier.
 The condensate collected from this unit is the light ethanol (74.23%) which is cooled
to 25°C.
 Rectifier used in this simulation is a distillation column which has to feed, one is
from Concentration Tower and other one is from Light Purification Tower.
 Concentrated ethanol (88.14%) is drawn out from this tower which is also cooled
to 25°C.
 Conventional distillation/rectification systems can produce ethanol at 92-95%
purity.
 The residual water and corn solids that remain after the distillation called
“stillage.” is then centrifuged to separate the liquid (thin stillage) from the solid
fragments (wet cake or distillers’ grains).
 The thin stillage is passed through evaporators to remove a significant portion of
the water to produce thickened syrup. Usually, the syrup is blended with the
distillers’ grains and dried to produce an animal feed called “distillers’ dried
grains with solubles” (DDGS).
Stillage, a liquid waste remaining after ethanol distillation, was collected and
characterized
REFERENCES
 Handbook of Industrial Chemistry, Volume 2, K.H. Davis, F.S. Berner.
 Sen, N. P., S. W. Seaman, B. P. -Y. Lau, D. Weber, and D. Lewis. 1995.
Determination and occurrence of various tetrahydro-β-carboline-3carboxylic acids and the corresponding N-nitroso compounds in foods
and alcoholic beverages. Food Chemistry. 54(3): 327- 337.
 Sree, N. K., M. Sridhar, L. V. Rao, and A. Pandey. 1999. Ethanol
production in solid substrate fermentation using thermotolerant yeast.
Process Biochemistry. 34: 115-119.
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