Alcohol FermentationGautham SenguttuvanM.Tech. Energy Systems

Manufacture of EthanolEnzymes

C6H12O6 2C2H5OH+2CO2+EnergySugar(Zymase Complex) (Ethyl Alcohol)• Primary Industrial Alcohol: Ethanol• Raw material used: Molasses(Cheap and readily

available in large quantities)• Micro-organisms used: Selected strains of the

yeast Saccharomyces cerevisiae(because they grow vigorously, have high tolerance for alcohol and have a high capacity for producing a large yield of alcohol)

Chemical Process• The chemical equations below summarize the

fermentation of sucrose (C12H22O11) into ethanol (C2H5OH). Alcoholic fermentation converts one mole of sucrose into four moles of ethanol and four moles of carbon dioxide, producing two moles of ATP in the process.

• The overall chemical formula for alcoholic fermentation is:• C6H12O6 + Zymase → 2 C2H5OH + 2 CO2Sucrose is

a dimer of two glucose molecules. In the first step of alcoholic fermentation, the enzyme invertase cleaves the glycosidic linkage between the two glucose molecules.

• C12H22O11 + H2O + invertase → 2C6H12O6

Chemical Process• Next, each glucose molecule is broken down into

two pyruvate molecules in a process known as glycolysis.[1]Glycolysis is summarized by the equation:

• C6H12O6 + 2 ADP + 2 Pi + 2 NAD+ → 2 CH3COCOO− + 2 ATP + 2 NADH + 2 H2O + 2 H+

• The chemical formula of pyruvate is CH3COCOO−. Pi stands for the inorganic phosphate.

• As shown by the reaction equation, glycolysis causes the reduction of two molecules of NAD+ to NADH. Two ADP molecules are also converted to two ATP and two water molecules via substrate-level phosphorylation.

Steps involved in the process• Water is added o bring down the sugar

concentration(30 to 40%)• Acid is added to adjust pH to fall in

acidic

Preparation of medium

• Temperature is adjusted and the yeast is mixed thoroughly with airAddition of

yeast• Fermentation process starts soon and

vigorous• Large quantity of CO2 is produced• Gas is collected, purified and used in other

industries

Fermentation

• Fermentation completes in 48 hours• Medium contains alcohol, other volatile

and unused constituents of the molassesSeparation of Ethyl Alcohol

• Purified with the help of rectifying columns and stored in bonded ware housePurification

Alcohol as beverages

•Ethyl alcohol is also formed as one of the products of fermentation during the manufacture of alcoholic beverages

•Different types of alcoholic beverages aer obtained by making use of the fermentation activity of different strains of yeast Saccharomyces

Brewery process

Malted Barley

•Malt is made by allowing barley to germinate with subsequent activation of natural enzymes, then halting so that a balance of sugars and starches is produced

•It provides all the essential nutrients for yeast growth and fermentation

Brewery process

Milling

•The malted barley stores is weighed according to the recipe and then slightly crushed and is known as grist

•Roller mills are set at controlled gaps so that the grain is cracked rather than powdered

Brewery process

Mashing

•The grist is mixed with water to form a mash which is carefully heated and agitated in the mash turn

•Under the controlled temperatures the natural enzymes begin converting the insoluble starches and proteins into a soluble malt extract known as wort

•This is a key step in the brewing process, as without maltose and other sugars, fermentation would not be possible

Brewery process

Lautering

•Lauter tun is a large filter where the dissolved sugars of the wort are separated from the spent grain, which mainly consists of malt husks

•After lautering the grain is sparged or rinsed to wash out the residual wort

Brewery process

Cane sugar

•Cane sugar is added in the syrup form during the boiling stage to provide a ready source of fermentable sugars for the yeast to turn into alcohol

•This sugar supplements the maltose•The difference between cane sugar and

malt sugar is that cane sugar is 100% fermentable, while the maltose is only 60% fermentable

Hops• Hops are the flowering portion of the hop vine.• These flowers not only fight off bacterial

infections in the beer, they aid in clarification of the beer, stabilize the flavor, help retain head, and aid in ones ability to drink the beer.

• Hop oils are produced in the Lupulin glands of the flower.

• The oils are made of α and β-acids, but α-acids contributes more to the bittering of a beer.

• These oils are non-polar, and can only be extracted through a short boiling

Brewery process

Boiling

•Boiling helps extract the bitter and aroma substances from the hops

•It sterilizes the wort and inactivated the malytenzymes, prior to the introduction of the yeast

•Average boiling time is between 45 and 90 minutes

Brewery process

Whirlpooling

•After boiling the wort is transferred to the whirlpool to remove solids know as trub

•This includes the hop residues and some protein from the malt

•These tanks have a large diameter to encourage settling

Brewery process

Wort cooling

•After the whirlpool, the wort must be brought down to fermentation temperatures (20–26°Celsius)

Brewery process

Yeast•Yeast is the power house of the fermentation

process•They are microscopic single celled organisms•Brewing yeast comes in two types- lager

yeasts and ale yeasts•Lager yeasts ferment at cool temperatures

and tend to sink at the bottom of the fermenting vessel

•Ale yeasts ferment at warm temperatures and rise to the top of the fermenter

What qualities should my yeast have?

• Rapid initiation of fermentation• High fermentation efficiency• High ethanol tolerance• Desired flavor characteristics• High genetic stability• Range of alcohol production

Fermenting

•Fermentation is the process in which the dissolved sugars are converted into alcohol and carbon dioxide

•Air and yeast are added to the cooled wort in the fermenting vessel

•The air provides oxygen to yeast to ensure a rigorous start to fermentation

•The duration of the process is about 4 to 5 days

Carbon dioxide

•CO2 is a natural gas produced as a byproduct of fermentation

•The gas is collected and is reused for carbonating the beer during the maturation and the filtration stages

Brewery process

Maturation

•This stage is also referred to as lagering•This stage involves the raw beer being

stored in lagering tanks at or slightly below 0 degC for 6 to 10 days

•It enhances shelf life by precipitation or settling of protein material

Brewery process

Filtering

•The hazy beer from the lagering tanks is filtered through a fine(diatomaceous) earth filter to remove yeast residue and haze particles

•At this stage the carbonation is also fine tuned using CO2 saved from fermentation

Various products of alcoholic fermentation

Beverage Substrate

Micro-organism(Saccharomyces)Species/Strain

Alcohol %

Wine Grape juice S.Ellipsoideus 10-12%

Beer Cereals S.Cerevisae 4-8%

Rum Black strap molasses S.Cerevisae -

Whisky Cereals S.Cerevisae 51-59%

Sake Starch(rice)Aspergillus oryzae, Lactobacillus and S.cerevisae

16%

Champagne Grape juice S.Cerevisae 12-13%

Brandy Wine S.Cerevisae 43-57%

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