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.
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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
Cellular Respiration: the process of using glucose to make energy (ATP) for the cell. Aerobic Cellular Respiration (requires oxygen) enzymes 6O2 + C6H12O6 6CO2 + 6H2O oxygen glucose carbon dioxide water ENERGY transfer between enzymes, other molecules ADP + Pi 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: C6H12O6 glucose 2CO2 + 2C2H5OH 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
Other products of fermentation - some are fermented by both yeast and bacteria Idli, Dosas, Kimchee, Sausage, Kefir, sauerkraut, miso, tempeh, tamari, chutney
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
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? Lactic acid Bacteria -------------------------> Lactose Lactic Acid (Milk sugar) Acid causes casein (milk protein) to denature and hold water into a semi-solid gel = yogurt
Milk Yogurt Bacteria produce acid Casein protein micelles (bundles) 10-7 meters in diameter 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 Fat globule
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 pre-treatment: Casein before heat pre-treatment: Casein after acid:
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