Ethanol can be produced through anaerobic fermentation of sugars and starches from various raw materials by yeast and bacteria. Saccharine materials like fruits, molasses, sugar beet and sugar cane directly provide fermentable sugars. Starchy materials like grains and tubers must be processed to break down starch into sugars through steps like milling, cooking, and conversion. The sugars are then fermented by organisms like Saccharomyces yeast to produce ethanol. The ethanol is recovered through distillation which separates ethanol (boiling point 78.5°C) from water (boiling point 100°C). Ethanol finds uses as a solvent, fuel, and chemical intermediate. Byproducts are also generated including

1. ETHANOL
PRODUCTON

2. Anaerobic Fermentation of alcohol

3.  Ethanol is used as
solvent
chemical intermediate
fuel
Solvent:-
Resins, pharmaceuticals , cosmetics ,household
cleaning products, industrial solvent
Fuel:-
Used as a bio fuel , In internal combustion engines
Chemical intermediate :-
• petroleum derived chemicals
• Butadiene production

4. Organisms for ethanol production:-
Bacteria:-
Many bacteria can produce ethanol
Many produce end products
• Other alcohol
• organic acids
• Polyols
• Ketones gasses
Many bac metabolize glucose by EMP pathway
• Clostridium sps
• Spirochaeta sps
• Sarcina sps
• Streptococcus sps

5. Yeast
Primary interest are saccharomyces sps
Organisms are selected by
• High growth and fermentation rate
• High ethanol yield
• Osmotolerance
• Low PH
• High temp
• Hardiness under physical and chemical stress
• Ethanol and glucose tolerance(allows conversion of
conc feeds to conc products)

6. RAW MATERIALS
Saccharine
Starch &
Cellulose materials

7. SACCHARINE:-
Simple, directly fermentable, 6 & 12 C molecules
Glucose, fructose, maltose
FRUITS:-
Grapes – 15%
Banana – 13.8%
Apples – 12.2%
Pineapples – 11.7%
Pears – 10%
Peaches – 7.6%
Oranges – 5.4%
Watermelon – 2.5%

8. MOLASSES:-
Beet or cane molasses
Contain 52 – 55 % fermentable
sugars
Molasses with above 15 – 20 %
sugar cont will need to be dilute
A ton yeild-70-80 gallons
CANE SORGUM :-
14% fermentable sugar content
Extraction requires heavy duty
13-14 gallons of alcohol / ton
Acidification is necessary

9. 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

10. Sugar beet sugar corn

11. Starchy materials:-
Materials that contain more complex carbohydrates
Grains :-
Grains must be milled, diluted & coked & fermented
Contain large amounts of fermentable materials
Alcohol yield is dependent on converted starch
Jerusalem artichokes :-
Abundant source of alcohol ( 16 – 18%) fermentable
material
A ton should yield about 25 gallons of alcohol
Material should be crushed to pulp & cooked for 2-
3 hrs, dilution is not necessary ( 79 – 80% water)

12. grains artichokes
potatoes sweet potato

13. PH is adjusted & fermentation is carried out
Potato:-
15 -18% fermentable sugar
A ton yield 20-25% of alcohol
Cooked with steam under pressure
After cooking mash is cooled to conversion for 15-20
min
Once converted PH should be adjusted mash is
fermented
Sweet potato:-
27-28% fermentable sugar
A ton should yield 40 gallons of alcohol
Similar manner to potatoes
Dilution is required (66%water)

15. Processing steps
Starchy materials are of 2 categories
1. Encased by grain hulls
2. Starch is readily available
Malting:-
Seeds are moistened & allowed to sprout
These seeds are powdered & the powder is called
malt
Milling:-
Grains are milled to expose the starch
Material is ground as fine as possible

16. But the fine flour is difficult to remove in distillation
process . Pot stills may reduce the problem
Cooking (preparation of mash):-
Starch is liquefied by boiling under pressure
To dissolve the water soluble starches
Always done with steam under pressure at 100°c
Use less water during cooking & water may be
added to dilute the mash
So cooling time may be saved
New method :- Milling & cooking in one operation
without use of water
 The cooked malt is called mash

17. Conversion :-
Conversion of starch to fermentable sugar (Maltose)
by certain enzymes in the malt or by acid hydrolysis
Enzyme extracts:-
Commercially available
3 basic types :
1. α amylase - produce dextrose
2. Β amylase - produce maltose
3. Gluco amylase – reduce the remaining starch

18. Acid hydrolysis:-
Conversion by the action of acid
Requires acid proof equipment and high temp
Dilute mineral acid(H₂SO₄) is added to grain slurry
Then immediately neutralized with calcium
hydroxide
Mash cooling:-
Mash is cooled after conversion & PH is checked
Cooling coils are used for cooling
Cooling time is reduced as much as possible

19. Fermentation
Batch fermentation is commonly employed.
Fermenter volume -- 600mᶟ.
3% inoculum(3×10⁶/ml)
With in 12 days yeast produce 10% ethanol
 when the process carried out at 35- 38°c , ph.4-4.5
max productivity was 1.9 g/h.
80%cells were removed in separator and brought
back again into fermenter.
When the high quality molasses is used, the max
yield is 95%.

20. Continuous fermentation not commonly used
In US 10 large scale plants among them 4 are used
con fermentation
Nutrient solution was molasses with di ammonium
phosphate
PH was adjusted to 5 with H₂SO₄
Fermentation temp -35°c
After fermentation cells were separated by
centrifugation and channeled back into the first
fermenter

22. PRODUCT RECOVERY
Cell biomass is separated by centrifugation or
sedimentation.
M.o desired end product – heated ( aggregate)
readily separated from broth by sedimentation.
Desired end product metabolite.
intracellular - n.a , vit ,enz, a.b (gresofulvin)
extracellular - a.a, acitic acid, citric acid, alcohol,
[ penicillin, streptomycin]

23. Separation of cell biomass
Flocculation flotation
Filtration centrifugation
flocculation:-
Flocculating agent is added
hydrocolloids
inorganic salts
organic poly electrolyte
 produce large aggregate which still settle more
readily

24. Flotation :-
by introducing gas into liquid
Cells gets adsorbed to the gas bubbles & rise to the
foam layer at the top of vessel
That can be collected & removed from the
bioreactor
Filtration:-
Bacterial cultures – absolute filters
 filamentous Fungi- depth filters
static & cross flow filtration

25. Distillation
Separation for a mixture of liquids
It relies on differences in B.P of component liquids
to be separated
The mixture to be separated is added to the
distilled pot & is heated
Low B.P will vaporize first. this vapors passes into
distilling head & then into condenser.
With in the condenser the vapor is cooled & it
liquefies.
The resulting liquid is then collected in receiving
flask

28. Ethanol B.P - 78.5°C
Water B.P - 100°C
Purification:-
By chromatography
HPLC
GLC
Applications
solvent in the manufacture of varnishes and
perfumes
Preservative for biological specimens
In the preparation of essence and flavorings

29. In many medicines and drugs.
As a disinfectant and in tinctures.
Used as a biofuel (99.2%).
Medically ethanol is soporific.
Used as antiseptic.
Fluid in many alcohol thermometer.
92.4%ethanol is used as solvent in cosmetics
pharmaceuticals and chemical industry
Byproduct
DDGS (distillers dried grain with solubles)
Co₂– used for the production of dry ice and preparation
of soft drinks
Yeast biomass- animal fodder (contains proteins &vit)