Various fermentation process and the subsequent products in the fermentation process are described in this short presentation.

1. FERMENTATIVE
METABOLISM
Submitted to :-
Dr. Tapas Choudhary
Professor
Dept. of Agril.
Microbiology,
IGKV
Submitted by :-
Sripati Abhiram Sahoo
M.Sc. (Ag.) 1st Year,
Department of PMBB
IGKV

2. Fermentation
• Features of fermentation pathways
• Pyruvic acid is reduced to form reduced organic acids or
alcohols.
• The final electron acceptor is a reduced derivative of
pyruvic acid.
• NADH is oxidized to form NAD: Essential for
continued operation of the glycolytic pathways.
• O2 is not required.

3. Fermentation
• Fermentation pathways are useful as tools in biochemical
identification.
• Also used in industry: Synthesis of certain organic
compounds.
• No additional ATP are made.
• Gasses (CO2 and/or H2) may be released.

4. Fermentation Pathways
• Glycolysis is the first stage of fermentation
• Forms 2 pyruvate, 2 NADH, and 2 ATP
• Pyruvate is converted to other molecules, but is not fully
broken down to CO2 and water
• Regenerates NAD+ but doesn’t produce ATP
• Provides enough energy for some single-celled anaerobic
species

5. Two Pathways of Fermentation
• Alcoholic fermentation
• Pyruvate is split into acetaldehyde and CO2
• Acetaldehyde receives electrons and hydrogen from
NADH, forming NAD+ and ethanol
• Lactate fermentation
• Pyruvate receives electrons and hydrogen from NADH,
forming NAD+ and lactate

6. Two Pathways of Fermentation

7. Examples of fermentation pathways
• Lactic acid fermentation
• Found in many bacteria;
e.g. Streptococcus sp, Lactobacillus acidophilus
• Mixed acid fermentation
• e.g. Escherichia coli
• Basis of the methyl red test
• 2,3-Butanediol fermentation
• e.g. Enterobacter aerogenes
• Basis of the Voges-Proskauer reaction

8. Alcoholic Fermentation

9. Muscles & LacticAcid Fermentation
• Muscle contains both slow twitch
fibers and fast twitch fibers.
• Slow twitch fibers contract and
fatigue more slowly than fast
twitch muscle fibers.
• Most of us have about 50% slow
twitch fibers and 50% fast twitch
fibers.
• Long-distance runners often have
more slow twitch fibers while
sprinters or bodybuilders often
have more fast twitch fibers.

10. The Twitchers (Twitch Muscle)
• Slow-twitch muscle fibers (“red” muscles) make ATP by
aerobic respiration
• Have many mitochondria
• Dominate in prolonged activity
• Fast-twitch muscle fibers (“white” muscles) make ATP by
lactate fermentation
• Have few mitochondria and no myoglobin
• Sustain short bursts of activity

11. Sprinters and Lactate Fermentation

15. End Products Of Fermentation
Other important fermentation end products
• Ethanol
(Saccharomyces cerevesiae)
• Propionic acid
(Propionibacterium)
• Acetone, buteraldehyde, and butanol
(Clostridium acetobutylicum)

16. Fermentation Pathway as a whole

17. Why does fermentation require extra
steps after glycolysis ?
• In fermentation, after
glycolysis, there are additional
steps to oxidize NADH (into
NAD+).
• Electrons and hydrogen ions
from the NADH that was
produced by glycolysis are
donated to another organic
molecule.
• No more ATP is created through
these additional steps.
• So essentially…
fermentation =
glycolysis + recycling of NAD+

18. HowAnaerobic Pathways End
• Fermentation pathways start with glycolysis
• Substances other than oxygen accept electrons at the end
of the pathways
• Compared with aerobic respiration, the net yield of ATP
from fermentation is small

19. Alternative Energy Sources in the
Body
• Pathways that break down molecules other than carbohydrates
also keep organisms alive.
• In humans and other mammals, the entrance of glucose and
other organic compounds into an energy-releasing pathway
depends on the kinds and proportions of carbohydrates, fats
and proteins in the diet.

20. Alternative Energy Sources in the
Human Body

21. Summery
• Fermentation products are wastes to cells that make them,
many are useful to humans(ethanol, acetic acid, and lactic acid).