Types of fermentation, how fermentation is used

1. FERMENTATION
• Classical Biotechnology
• Humans have been using this technology for
centuries
• Involves harnessing the wastes of bacteria
and/or yeast for products that humans
consume
• Big business

2. Cellular Respiration: the process of using
glucose to make energy (ATP) for the cell.
Aerobic Cellular Respiration (requires oxygen)
6O2 + C6H12O6 6CO2 + 6H2O
oxygen glucose carbon dioxide water
enzymes
ADP + Pi
ENERGY transfer
between enzymes,
other molecules
ATP

3. •Aerobic Cellular Respiration takes place
in the mitochondria of cells.
•It can provide up to 38 molecules of ATP
per molecule of glucose.

4. Anaerobic Cellular Respiration (without oxygen)
also known as Fermentation
Alcoholic Fermentation:
C6H12O6
glucose
•provides 2 molecules ATP per glucose
•done by yeast
2CO2 + 2C2H5OH
carbon dioxide ethanol

5. Products of Alcoholic Fermentation
don’t drink alcohol

6. Making Rootbeer: 6 simple steps
• Heat Water to ~40 degrees C (yeast like it)
• Add sugar and dissolve
• Add root beer extract
• Add yeast
• Ferment @ ~27 degrees C
• Chill and enjoy!

7. Lactic Acid Fermentation:
Glucose carbon dioxide + lactic acid
•provides 2 molecules ATP per glucose
•done by muscle cells
•done by bacteria cells

8. Products of Lactic Acid Fermentation

9. Other products of fermentation - some are
fermented by both yeast and bacteria
Idli, Dosas, Kimchee, Sausage, Kefir,
sauerkraut, miso, tempeh, tamari,
chutney

10. More products of fermentation

11. Yogurt
Yogurt-like products have been made for millenia across Eastern Europe,
North Africa, Central Asia and India.
Contains bacteria that are “thermophilic” = heat loving

12. Two main types of Lactic Acid Bacteria
(Identified around the year 1900):
Traditional spontaneously fermented milks contain species that
can reside in the human digestive tract:
• Lactobacillus fermentum,
• L. casei
• L brevis
• L plantarum (from picked vegetables)
• L acidophilus
Lactobacillus
• meaning “milk” and “rod”
• over 50 different species
• found on plants and in the digestive system of animals such as cows and humans.
Lactococcus
• meaning “milk” and “sphere” because of its shape
• found primarily on plants
• less common than lactobacillus

13. Commercial Yogurt
Contains 2 species of bacteria specialized to grow well in milk (but can’t
survive inside the human body):
First,
Streptococcus
thermophilus is
more active,
then slows
down when
acidity reaches
0.5%
Next,
Lactobacillus
bulgaricus is
more acid
tolerant and takes
over until acidity
>1%
These bacteria work in symbiosis. Each bacterium stimulates the growth
of the other => acidifies the milk more rapidly than either partner on its
own.

14. Milk is
•Water
•Protein (casein and whey)
•Fat
•Sugar (lactose)
•Vitamins
• Minerals

15. Lactose
Lactic acid Bacteria
------------------------->
Acid causes casein (milk
protein) to denature and
hold water into a semi-
solid gel = yogurt
(Milk sugar)
How Does Milk Turn Into Yogurt?
Lactic Acid

16. Milk Yogurt
Bacteria produce acidCasein protein micelles
(bundles)
10-7 meters in diameter
Fat
globule
Acid causes
Casein bundles to
fall apart into
separate casein
molecules.
These rebind to
each other in a
network that traps
water.
=> makes a gel

17. Making Yogurt in 4 Simple Steps
1. Start with Cow, Sheep, or Goat milk.
Casein before heat
pre-treatment:
Casein after heat
pre-treatment: Casein after acid:
2. Heat milk to 80 °C. Two purposes:
• destroy existing bacteria
• “condition” the proteins = begins the denaturing process
(a whey protein molecule binds to a casein molecule which disrupts the casein bundles
allowing them to make short branched micelle chains)
3. Cool milk to 40 °C and innoculate with bacteria
4. Incubate at 30 °C to 45 °C

18. Incubation Temperature
• 40-45 °C takes 2-3 hours
Produces a coarse protein network with thick strands give firmness but easily leak whey
(a process called syneresis - the separation of liquid from the gel)
• 30 °C takes 18 hours
Produces a finer more branched delicate network that holds the liquid whey