FERMENTATION
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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
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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
ATPATP
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•Aerobic Cellular Respiration takes place in the mitochondria of cells.
•It can provide up to 38 molecules of ATP per molecule of glucose.
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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
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Products of Alcoholic Fermentation
don’t drink alcohol
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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!
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Lactic Acid Fermentation:
Glucose carbon dioxide + lactic acid
•provides 2 molecules ATP per glucose
•done by muscle cells
•done by bacteria cells
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Products of Lactic Acid Fermentation
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Other products of fermentation - some are fermented by both yeast and bacteria
Idli, Dosas, Kimchee, Sausage, Kefir, sauerkraut, miso, tempeh, tamari, chutney
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More products of fermentation
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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
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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
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Commercial YogurtContains 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.
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Milk is
•Water
•Protein (casein and whey)
•Fat
•Sugar (lactose)
•Vitamins
• Minerals
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LactoseLactic 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
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Milk YogurtBacteria 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
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Making Yogurt in 4 Simple Steps1. Start with Cow, Sheep, or Goat milk.
Casein before heatpre-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 bacteria4. Incubate at 30 °C to 45 °C
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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