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1. FERMENTATION AND TYPES
M. Chatiyaa
II –M.Sc Microbiology
Department of Microbiology
Sacred Heart College (Autonomous)

2. FERMENTATION
Fermentation is a metabolic process through which
microorganisms convert organic compounds
particularly sugars into simpler substances such as
alcohol, acids, and gases under anaerobic or low-
oxygen conditions.
The term fermentation was coined by Louis Pasteur.
The science of fermentation called Zymology.

3. ALCOHOLIC FERMENTATION
Alcoholic fermentation is an anaerobic
process where yeast and bacteria
(Saccharomyces cerevisiae, Zymomonas
mobilis) convert sugars (mainly glucose,
fructose, and sucrose) into ethanol and
carbon dioxide.
Applications
 Beer and wine production.
 Production of ethanol as a biofuel.

4. LACTIC ACID FERMENTATION
In this process, lactic acid bacteria (LAB)
(Lactococcus lactis, Lactobacillus acidophilus)
convert sugars into lactic acid.
It occurs in two forms namely, Homolactic
fermentation produces only lactic acid and
Heterolactic fermentation produces lactic acid
along with ethanol and carbon dioxide.
 Application
 Yogurt and cheese production

5. ACETIC ACID FERMENTATION
 Acetic acid bacteria (Acetobacter
aceti, Acetobacter pasteurianus)
oxidize ethanol into acetic acid in
the presence of oxygen.
 Application
 Vinegar production

6. BUTYRIC ACID FERMENTATION
 Performed by obligate anaerobic bacteria,
particularly (Clostridium butyricum,
Clostridium acetobutylicum) this process
breaks down sugars into butyric acid,
hydrogen gas, and carbon dioxide.
 Application
 Fermentation in silage
 Production of butyric acid for industrial
uses.

7. PROPIONIC ACID FERMENTATION
 Carried out by Propionibacterium species
(Propionibacterium freudenreichii), this
process generates propionic acid, acetic
acid, and carbon dioxide.
 Application
 Swiss cheese production, which results
in characteristic holes and flavor.

8. FORMIC ACID FERMENTATION
 In Formic acid fermentation the pyruvate is
metabolized to Formic acid as a primary
product, often along with other compounds
such as carbon dioxide (CO ), hydrogen (H ),
₂ ₂
and organic acids by (Clostridium butyricum).
 Application
 Used as a chemical precursor in leather
tanning, textile dyeing, and as an
antibacterial agent.

9. GLUCONIC ACID FERMENTATION
 (Aspergillus niger and Penicillium
chrysogenum) are capable of oxidizing
the aldehyde groups of glucose to
Gluconic acid.
 Application
 Used to improve dough stability and
texture in bread and bakery
products.

10. MIXED ACID FERMENTATION
 In this process, bacteria like Escherichia coli
produce a variety of organic acids (lactic, acetic,
formic) along with gases like hydrogen and carbon
dioxide.
 Application
 Initiates acidification by producing lactic and acetic
acids, preserving and enhancing the flavor of
fermented vegetables (Sauerkraut and Pickle)
 Contributes to flavor and preservation in soy
sauce, miso.

11. BUTANEDIOL FERMENTATION
 Performed by bacteria such as
Enterobacter and Klebsiella, this process
produces 2,3-butanediol along with other
byproducts like ethanol, lactic acid, and
carbon dioxide.
 Application
 Industrial production of solvents like
butanediol.

12. HYDROGEN GAS FERMENTATION
 Certain anaerobic bacteria (Clostridium
acetobutylicum, Clostridium butyricum)
ferment organic matter to produce
hydrogen gas as a byproduct.
 Application
 Biohydrogen production

13. METHANOGENIC FERMENTATION
 Methanogens (archaea) produce
methane gas by converting organic
acids, alcohols, or hydrogen and carbon
dioxide.
 This is a key step in anaerobic
digestion.
 Application
 Biogas production

14. MALOLACTIC FERMENTATION
 This is a secondary fermentation in
winemaking, where malic acid is
converted into lactic acid and carbon
dioxide, softening the wine's flavor.
 The LAB are primarily involved in
Malolactic fermentation.
 Application
 Conversion in red and white wines to
enhance taste.

15. THANK YOU