FERMENTATIONClassical BiotechnologyHumans have been using this technology for centuriesInvolves harnessing the wastes of bacteria and/or yeast for products that humans consumeBig businessCellular 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 waterenzymesADP + PiENERGY transfer between enzymes, other moleculesATPAerobic 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 FermentationAlcoholic Fermentation: C6H12O6 glucose provides 2 molecules ATP per glucosedone by yeast2CO2 + 2C2H5OH carbon dioxide ethanolProducts of Alcoholic Fermentation

dont drink alcohol

Making Rootbeer: 6 simple stepsHeat Water to ~40 degrees C (yeast like it)Add sugar and dissolveAdd root beer extractAdd yeastFerment @ ~27 degrees CChill and enjoy!Lactic Acid Fermentation: Glucose carbon dioxide + lactic acidprovides 2 molecules ATP per glucosedone by muscle cellsdone by bacteria cellsProducts 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, chutneyMore products of fermentation

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):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 lactobacillusCommercial YogurtContains 2 species of bacteria specialized to grow well in milk (but cant 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 isWaterProtein (casein and whey)FatSugar (lactose)Vitamins MineralsLactoseLactic 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

MilkYogurtBacteria produce acidCasein protein micelles (bundles)10-7 meters in diameter Fat globuleAcid causes Casein bundles to fall apart into separate casein molecules. These rebind to each other in a network that traps water. => makes a gelMaking 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 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