1. Process Overview
Starch To Alcohol conversion
By Praveen Kumar
Pioneer Distilleries Nanded
(Diageo India)
2. Basic Process
Raw Material receipt Preparation for Fermentation
Distillation Fermentation
Co products & effluent handling
3. Basic Process
This effectively remains the same for all processes
Feedstock preparation
Fermentation
Distillation
•However there are significant differences which are
addressed at a high level in this presentation but dealt
with in some detail in the rest of the course
4. Carbohydrates and Fermentable Sugars
• Carbohydrates, or “hydrates of carbon,” are an important group of
naturally occurring organic compounds.
•Commonly these are formed by green plants through photosynthesis
• Carbohydrates are any of the various compounds comprised of
• carbon, hydrogen and oxygen, general formula Cx(H20)y
• Carbohydrates are used to store energy until required by the organism
– Sugars, starches, cellulose, glycogen and related substances
• Saccharides, the simplest form of carbohydrates, consist of single
sugar units with five or six carbon atoms in ring form
– They are commonly called “sugars” or “sweeteners”
5. Carbohydrates and Fermentable Sugars
•Starch and cellulosic compounds are polymeric molecules
•– Made up of basic unit called monomers
•– These monomers are joined together by a chemical bond
called a glycosidic link
•Carbohydrates can be divided into four basic classes
•– Monosaccharide's
•– Disaccharides
•– Oligosaccharides
•– Polysaccharides
•Each of these comprises of successively more of the
same basic unit or units
6. Carbohydrates and Fermentable Sugars
1.Monosaccharide:
– Glucose and Fructose
Can be fermented to ethanol by yeast, only under anaerobic conditions
2.Disaccharides :
– Sucrose and Maltose
– Sucrose is fructose and glucose molecule linked together
– Sucrose is obtained from sugar cane and sugar beets
– Commonly known as table sugar
– Maltose comprises of two molecules of glucose linked together
– Both maltose and sucrose are fermentable to ethanol by yeast
3.Oligosaccharides:
– Are Saccharides with more than three but less than eight units
– Oligosaccharides can not be fermented by yeast to produce ethanol
4.Polysaccharides:
– Polymeric carbohydrates of many thousand of monomeric sugar units linked
together through glycosidic linkages
– Starch, glycogen or cellulose
– Neither starch or cellulose can be directly fermented by yeast to produce
ethanol
– Must be hydrolyzed to fermentable sugars
8. STARCH (A LITTLE MORE COMPLICATED)
Good well understood feedstock.
•Long chains of glucose molecules.
•Consists of: Grains
Tubers (potato, cassava)
Rice
Starch chains need to be broken down before fermentation.
9. Starch (a little more complicated)
• The basic chemical formula of starch
• (C₆ H₁₀O₅)n is similar to glucose, C₆H₁₂O₆, where
'n' is the number of Glucose molecules present.
There are two forms of starch:
• Amylose, the branchless form
• Amylopectin, the branched form.
• The main function of starch is as way to store
energy for plants
10. DEGREE OF POLYMERIZATION (DP)
Glucose = DP1
These can
Maltose = DP2 be fermented
by yeast
Maltotriose = DP3
Four or more glucose molecules = DP4+
Dextin
Malto-dextrin
Oligosaccharide
Maltose
Glucose
1000
100
10
1
13. Fermentation Starch
• Maintain correct sugar
balance
• Most common method is
Simultaneous
Saccharification and
Fermentation (SSF)
• Very high alcohols
possible but good cooling
is essential.
14. Enzymes
•Enzymes are a type of protein present in, and essential to, all
living things
•Enzymes act as biological catalysts
They increase the rate of chemical reactions without
undergoing any permanent change themselves
•Enzyme are not consumed in the reaction Can continue to
catalyze a reaction as long as the proper reactants
are available
•The surface of each enzyme contains various chemical groups
that can react with small molecules
17. Liquefaction
Dextrinswollen starch molecules
Liquefaction is the process of turning starches, into smaller molecules
called dextrins
– Alpha amylase (AA) enzyme is need for Liquefaction
– Granular structure of starch needs to be broken before AA can bring
about hydrolysis of starch to dextrins
– AA breaks randomly breaks alpha 1,4 glucosidic linkages but not alpha
1,6 linkages
18. Saccharification
•New dry grind ethanol plants do
Simultaneous Saccharification and Fermentation (SSF)
•Some plants still have separate saccharification process
20. Starch Advantages
• If dried can be stored easily between harvest.
• Uses conventional well understood process.
• Cooking process kills most bacteria.
• With grains a high protein feedstock is a by-product.
• High fermentation alcohols and high yields are
obtainable.
• Possibility of other valuable by-products.
21. Disadvantages
• Feed stock is often also a food or grown on the same land
• Lower yield of alcohol per acre than sugar.
• Lower overall net energy gain compared with sugar. Due to
the gelatinization requirement of the starch (cooking)
• Higher chemical costs compared to sugar Due to the
addition of commercial enzymes or the use of malted
grains
25. Juice (Beet or cane)
• Advantages
• Rapid fermentation
• Extra nutrients not usually required
• No up front energy needed for concentration
• Effluent easy to treat or recycle
• Disadvantages
• Low alcohol fermentations
• Cannot be stored
• Usually contaminated (low pH or antimicrobials)
• Molasses or concentrated juice often added to increase sugar content.
26. Distillation Juice
• Distillation is straight forward and not high fouling.
• Beverage: Generally a highly flavoured product
• Batch and continuous distillation to produce Cachaça in
Brazil also rum in Haiti and Dominican Republic.
• Fuel Common to use juice during the campaign, often
fortified with molasses or syrup to reduce the amount
of water that needs to be removed.
28. What is High Test?
• Juice concentrated to
60 to 70% sugar
• No sugar is removed
29. Why use it?
• Advantages:
• Vinasse can be used
• Little sugar lost to Maillard reaction
• Can be stored
• Can be diluted to optimum strength for fermentation
• High alcohols possible
• Disadvantages:
• Extra energy to remove water
• Nutritional supplements, minerals and FAN needed
31. Points to Remember
• No one makes Blackstrap Molasses as a product. It is a
waste product of sugar production. As such, the alcohol
plant receives all the molasses plant upsets, poor storage
conditions, added chemicals and efficiency improvements.
Even previously used molasses can be added.
• Very high mineral content
• And as such it is a very variable product and its overall
distilling quality is constantly declining.
• You need to account for this in plant design and operations.
32. Types of molasses
• A Type one crystallization
step rare but good feed
stock if handled properly.
• B Type two crystallization
steps
• C Type three crystallization
steps. Most common form
of blackstrap
• Refiners From the cleanup
of the raw sugar. Lower
minerals higher sugar. May
contain alpha-amylase.
36. Sucrose structure
• Invertase: is an enzyme produced by the yeast which
breaks down sucrose into glucose and fructose. This allows
the two sugars to be transported through the cell
membrane. High test molasses is sometimes treated with
invertase to prevent the crystallization of the sucrose.
.
37. Fermentation
• Fermentation allows Glycolysis to continue making
ATP when oxygen is unavailable.
• Anaerobic process
• Glycolysis will happen the same way it does at the
beginning of cellular respiration
– Glycolysis splits glucose into two pyruvic acid molecules
– Pyruvic acid and NADH enter Fermentation
38. Fermentation
• Fermentation will occur instead of cellular respiration
due to the lack of oxygen
• Occurs in the cytoplasm of cells
• Fermentation does not produce ATP
39. Two Types of Fermentation
• Lactic Acid
• Alcoholic
40. Alcoholic Fermentation
• Alcoholic fermentation
– Yeast and certain bacteria
– Pyruvate is broken into alcohol and carbon dioxide
– Used in the production of beer, wine and bread
42. Points in Fermentation
• Stress can be high
• Incremental feed reduces
stress
• Once dilution water is
added becomes very
susceptible to bacterial
action
• High solids can result in
sludge in fermenter and
wash column
46. Co product / Effluent handling
• This varies dependant on
• Feedstock
• Country (regulatory and permissible)
• Plant design
47. Starch based
• Because of the “high solids content” and the
analysis of the remaining product a valuable
animal feed is possible
• In some countries “zero discharge” is required,
which can require significant recycling of
material
• Generally can produce a High COD / BOD
effluent that can be treated or discharged
with permission
48. Sugar Based
• Here the remaining solids are much lower value
and are generally used in co-generation systems
supplying both heat and power for the plant
• Liquid discharge is either treated and discharged
or simply discharged. In some areas it can be land
applied as a mineral fertilizer
• Molasses based production generally produced a
very dark and very low value and hard to dispose
of effluent. Recent methods of incineration are
showing reasonable success
