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The Economic importance of yeast

The Economic importance of yeast. İrem Gaye Kars Lider Serçemeli. Objectives. To appreciate that some microorganisms are useful to humans To recall an equation for anerobic respiration To understand the industrial production of alcohol and bread. Let’s learn bread production.

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The Economic importance of yeast

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  1. TheEconomicimportance of yeast İrem Gaye Kars Lider Serçemeli

  2. Objectives • Toappreciatethatsomemicroorganismsareusefultohumans • Torecall an equationforanerobicrespiration • Tounderstandtheindustrialproduction of alcoholandbread

  3. Let’slearnbreadproduction FİRST STEP • Flour , sugar , waterand salt aremixedwithyeast.Thisprocess is calledkneadingandproducesdough.

  4. SECOND STEP Thedough is rolledintoshape , thenkept in a warm (about 28 C) , moistenviroment. Theyeastfermentsthesugar , andthebubbles of carbondioxidearetrappedbythestickyproteins of thedough.Thedoughexpandsorrises.

  5. THİRD STEP Cooking at 180 celcius – baking: • Killstheyeastandstopsfermentation • Causesalcoholtoevaporate • Hardestheouthersurfaceto form a crust.

  6. FİNAL STEP Theproduct is bread, whichshould be : • Spongy in texture , because of trappedcarbondioxide. • Freshsmelling (partlyalcoholvapour !).

  7. Yeastperformsalcoholicfermentation • Much of commercialuse of microorganisms is based on theprocess of fermentation. Thistermcoversanymetaabolicprocesscarriedoutbymicroorganisimsusingcarbonhydrate as startingmaterial.Thebest-knownfermentationreaction is anaerobicrespiration of glucosebysingle-celledfungusyeast :

  8. Carbondioxide + ethanol + energy • Glucose Since one of theproducts is ethanolthisprocess is oftenknown as alcoholicfermentation.As well as makingalcohol , thecarbondioxideproduced is valuablecommercially.Fortheyeast , theusefulproduct is energy – thealcoholandcarbondioxideareby – products.

  9. Alcoholhas a highenergycontentand is toxic Alcoholcontains a greatdeal of energy , a factthat is exploitedwhenalcohol is used as a fuelsource.Alcohol is alsotoxic (poisonous) andtheyeastexcretes it intothesurroundingsliquidmedium.Ifthealcoholconcentration in themediumgetshigherthen 8-9% , theyeast is killedandfermentationstops.

  10. Fineturningthefermentationprocess Because of theenormouscommercialsignificance of theseprocessesmuchresearch has goneintomakingthem as efficent as possible .Forexample : • Strains of yeastthataretoleranttohigherconcentrations of alcoholhavebeendeveloped • High-yieldingstrains of barleyhavebeenselectivelybred . • Geneticengineershavedevelopedyeastswhich can coverstarchtomaltose, andthusremovetheneedforthemaltingstages.

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