Aerobic and Anaerobic Fermentation

1. Aerobic & Anaerobic fermentation
BEENISH SARFRAZ

2. FERMENTATION:
 is the conversion of carbohydrates (plant foods) to alcohols
and carbon dioxide, or organic acids, using yeasts, bacteria,
or a combination of that, under anaerobic (no oxygen)
conditions
 implies that the action of microorganisms is desirable
 complex organic compounds, such as glucose, are broken
down by the action of enzymes into simpler compounds
without the use of oxygen.
 Fermentation results in the production of energy in the
form of two ATP molecules, and produces less energy than
the aerobic process of cellular respiration
 C6H12O6 2CO2 + 2C2H5OH + 2 ATP

3. CHEMISTRY OF FERMENTATION:
Fermentation
Energy difference in
respiration & fermentation

4. HISTORY:
 The chemistry of fermentation were first investigated
by Louis Pasteur in 1860
 He called the process la vie sans air, or life without air
 In 1897, Hans and Eduard Beuchner discovered that
fermentation could occur in a cell-free extract of yeast
 This work led to the elucidation of the enzymes involved
Micro-organisms involved:
•Saccharomyces: ethyl alcohol and carbon dioxide
•Streptococcus and Lactobacillus: lactic acid
•Escherichia coli: acetic acid, succinic acid
•Clostridium: butyric acid, butyl alcohol, acetone

5.  Conversion of complex organic compounds into
simpler ones in the complete absence of oxygen
Glycolysis:
• Before any of the anaerobic fermentation takes place a
process called Glycolysis takes place
• It is the conversion of Complex organic compounds like
Glucose into simpler 3C containing compound Pyruvic acid
• 2 molecules of ATP are produced
• This step takes place in the cytosol of the cell
C6H12O6 + 2 ADP + 2 Pi + 2 NAD+ → 2 CH3COCOO− + 2 ATP
+ 2 NADH + 2 H2O + 2 H+

6. Summary of Glycolysis

7. ALCOHOLIC FERMENTATION:
 Ethanol fermentation converts two pyruvate molecules, the
products of glycolysis, to two molecules of ethanol and two
molecules of carbon dioxide with the help of Zymase enzyme.
C6H12O6 + Zymase→ 2 C2H5OH + 2 CO2

8. LACTIC ACID FERMENTATION:
HOMOLACTIC HETEROLACTIC

10. Aerobic Fermentation:
• “Aerobic” means “in the presence of oxygen”
• Aerobic fermentation is actually wrong term
• Organisms use oxygen for the conversion of complex organic
compounds, but process is known as aerobic respiration
• Some types of fermentation processes require oxygen
• Oxygen is required for the reproduction and growth of
microorganisms (Yeast/Bacteria etc)
• Yeast requires oxygen for a number of processes essential for
reproduction
• Most fermentation involves the initial introduction of oxygen
to ensure a strong yeast colony is established. And
• yeast will ferment without using oxygen even if oxygen is
available

11. Fermentation process is used:
 To produce antibiotics if no other method is available
 To produce ethyl alcohol which can be used as gasohol
 To produce alcoholic beverages like beer from barley or wheat
and wine from grapes
 Used to store vegetables in the form of pickling
 Yogurt is produced by fermentation of milk
 Cheese is also produced by the action of yeast on milk
 is used in the treatment of wastewater. In the activated
sludge process, aerobic bacteria are used to ferment organic
material in wastewater. Solid wastes are converted to carbon
dioxide, water and mineral salts.