FERMENTATION Classical Biotechnology Humans have been using this

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

Cellular Respiration: the process of using glucose to make energy (ATP) for the cell. Aerobic Cellular Respiration (requires oxygen) 6 O 2 + C 6 H 12 O 6 oxygen glucose ADP + Pi enzymes ENERGY transfer between enzymes, other molecules 6 CO 2 + 6 H 2 O carbon dioxide water ATP

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

Anaerobic Cellular Respiration (without oxygen) also known as Fermentation Alcoholic Fermentation: C 6 H 12 O 6 2 CO 2 + 2 C 2 H 5 OH glucose carbon dioxide ethanol • provides 2 molecules ATP per glucose • done by yeast

Products of Alcoholic Fermentation don’t drink alcohol

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!

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

Products of Lactic Acid Fermentation

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

More products of fermentation

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

Two main types of Lactic Acid Bacteria (Identified around the year 1900): 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 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

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.

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

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

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

Making Yogurt in 4 Simple Steps 1. Start with Cow, Sheep, or Goat milk. 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 Casein after heat Casein before heat Casein after acid: pre-treatment:

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