Acetic Acid Fermentation

1. • Acetic Acid Fermentation
• By Sunbal Mirza.

2. Acetic acid
 Acetic acid is systematically known as ethanoic acid having formula CH3COOH.
 It Is colourless, liquid organic compound.
 It has a pungent vinegar like smell.
 Melting point is 16-17 degree centigrade.
 Boiling point is 118.0 degree centigrade.
 It is soluble in polar solvents and insoluble in non polar solvents.
 It is principle constituent of vinegar.
 Undiluted ,pure acetic acid (99.98%) is called glacial acetic acid.

3. Acetic acid fermentation
• a process of oxidation in which alcohol is converted into acetic acid by the
agency of e.g. bacteria of the genus Acetobacter, especially A. aceti (as in
the production of vinegar from cider or wine)
Types:
• Acetic acid fermentation is of 2 types:
1. Anaerobic fermentation
2. Aerobic fermentation

4. Anaerobic acetic acid Fermentation
• Single step process.
• Species of anaerobic bacteria, including members of the genus Clostridium
or Acetobacterium can convert sugars to acetic acid directly without
creating ethanol as an intermediate. The overall chemical reaction conducted
by these bacteria may be represented as:
• C6H12O6 → 3 CH3COOH
• These acetogenic bacteria produce acetic acid from one-carbon
compounds, including methanol, carbon monoxide, or a mixture of carbon
dioxide and hydrogen:
• 2 CO2 + 4 H2 → CH3COOH + 2 H2O

5. Aerobic acetous fermentation
• 2 step process
• First step involves yeast utilization to produce alcohol from sugar.
• Second step is utilization of acetic acid bacteria to oxidize ethanol into acetic
acid through acetaldehyde.
• The microbial oxidation of ethanol to acetic acid is an aerobic fermentation that
has high oxygen requirement.
• Two oxidation steps occur during the conversion of ethanol to acetic acid. In
the first step ethanol is oxidized to acetaldehyde in the presence of NAD or
NADP and in the second step acetaldehyde is changed to acetic acid and
render the catalytic action of the enzyme alcohol dehydrogenase .

6. Conti….
• In this oxidation one liter of 12% acetic acid is produced from one liter of 12% alcohol
that is one mole of acetic acid is formed from one mole of alcohol.

8. Industrial production
Substrates used…
Commonly used substrates used in
industry are
• Ethanol
• wine and whey
• Molasses, fermented grains malt and
rice etc.
Microbes :
1: Acetic acid bacteria (AAB)
2:
acetobacterium(Genus)(aceti.,xylinum
sp.)
3:clostridium (Genus)(thermoaceticum
sp.)
• Properties of microbes used…
Strains of microbes used for
commercial acetic acid production
should be
• Tolerant to high acetic acid conc.
• Should require small amount of
nutrients
• not over oxidizing to the product
formed
• High temp. tolerant
• Low PH tolerant
• Provide high yield

9. fermentation Processes used in
industry…
• Continuous fermentation
• Batch fermentation
• Submerged fermentation
• Surface fermentation

10. Continuous fermentation
• ORLEANS METHOD
• Slow , Old and traditional method.
• High grade vinegar is used as starter culture.
• Fermentation is done in large containers , filled 2/3 of capacity.
• wooden containers are laid down and holes are drilled at top and bottom of barrels.
• Ethanol is poured into them and then starter culture is added.
• Ethanol is converted into acetic acid within 35
days(5weeks).
• Temp. is kept at 21-29 degree centigrade.
• results:
• High quality(aged) acetic acid

12. Surface fermentation
• Also known as trickling system or German process.
• Trickling generator is used as fermenter it is usually made up of wood with its inner surface
lined with vinegar- moistened beech wood shavings.
• Acetic acid bacteria are also incorporated in it.
• The substrate alcohol is poured from top which tickles through wood shavings.
• Air is introduced in it
• When alcohol reaches the bottom of fermenter ,within span of 3-4 days it has been converted
into acetic acid. (80-88% yield )
• CONDITIONS:
• pH 2.5-3.3
• Temp.20-30 degree centigrade +proper aeration

14. Submerged fermentation
• Faster and more efficient method, produces highest yield with improved quality.
• Fermenters used in in this process are usually Acetators and Caviators.
• on industrial level ,Fermenters consist of large steel tanks with capacity of 10,000-
40,000L,air supply , cooling system, foam controlling system(foam eliminators),loading and
unloading valves.
• This process of acetic acid production is semi-continuous , automated process.
• AAB cultures ,ethanol ,acetic acid from previous batch and nutrients are added into fermenter
as starting media.
• System is aerated on large scale .
• Heat exchangers control the temperature and foam eliminators control foaming in fermenter.

15. Conti…
• After 35hrs at 40 degree centigrade obtained acetic acid yield by tis process is approx.98%.
• Recovery:
• turbid acetic acid is the final product due to presence of AAB that need to be filtered.
• Plate filters are generally used and bacterial cell are removed by cross flow micro filtration,
nano -filtration etc.
• After filtration potassium FerroCyanide is used to decolorize the final product if require.
• In industry , more preferably submerged fermentation is used for acetic acid production.

17. Batch fermentation
• In this fermentation, all nutrients, bacterial cultures and substrate are added and optimum
conditions like aeration ,pH and temperature are maintained in the fermenter and process
starts.
• In this process , in start production rate is almost zero then starts increasing and suddenly
increases exponentially and then goes on decreasing as nutrients start depleting in
fermenter.
• when fermentation completes all of the material is removed and crude product is purified
and process is repeated .
Drawbacks:
• more chances of contamination as quality can be checked after the batch not
during process.

18. thank you