Good MicrobesGood Microbes

Fermentation ProcessFermentation Process

Goal of MetabolismGoal of Metabolism

Utilize food (sugars) in order to Utilize food (sugars) in order to store energy in the form of ATP. store energy in the form of ATP. Differences between prokaryotes Differences between prokaryotes and eukaryotes.and eukaryotes.

Therefore, the production of alcohol, Therefore, the production of alcohol, rising bread, souring of milk (yogurt rising bread, souring of milk (yogurt and cheese) are bi-products of and cheese) are bi-products of organisms attempting to make ATP.organisms attempting to make ATP.

Metabolism with OxygenMetabolism with Oxygen

Yeast Metabolism in Wine Yeast Metabolism in Wine MakingMaking

C6H12O6    ====>   2(CH3CH2OH)      +        C6H12O6    ====>   2(CH3CH2OH)      +        2(CO2)  2(CO2)    Sugar      ====>        Alcohol             +     Sugar      ====>        Alcohol             +   Carbon dioxide gas Carbon dioxide gas (Glucose)               (Ethyl alcohol) (Glucose)               (Ethyl alcohol)

Yeast metabolism often begins as an aerobic Yeast metabolism often begins as an aerobic condition in which the yeast multiply rapidly, condition in which the yeast multiply rapidly, then switches to an anaerobic condition in which then switches to an anaerobic condition in which the fermentation process takes place.the fermentation process takes place.

SummarySummary

In the anaerobic condition, yeast will In the anaerobic condition, yeast will yield only 2 ATP’s per molecule of yield only 2 ATP’s per molecule of glucose, plus ethanol and CO2. glucose, plus ethanol and CO2.

While this works for good wine, the While this works for good wine, the level of ethanol soon becomes too level of ethanol soon becomes too concentrated and actually kills the concentrated and actually kills the yeast that produced it.yeast that produced it.

Therefore, yeast are considered Therefore, yeast are considered falcultative anaerobes.falcultative anaerobes.

Wine MakingWine Making

Wine is usually made from grapes because it Wine is usually made from grapes because it has the right balance of natural sugars, has the right balance of natural sugars, nutrients and pH for the yeast to work.nutrients and pH for the yeast to work.

Yeast converts the sugars to alcohol and CO2, Yeast converts the sugars to alcohol and CO2, we let the CO2 dissipate before bottling.we let the CO2 dissipate before bottling.

Yeast dies after sugar is gone (or alcohol Yeast dies after sugar is gone (or alcohol content kills them)content kills them)

Specialized yeasts (wine yeasts) are able to Specialized yeasts (wine yeasts) are able to withstand higher levels of ethanol than bread withstand higher levels of ethanol than bread yeasts.yeasts.

ATP Yield Without ATP Yield Without OxygenOxygen

ATP Yield With OxygenATP Yield With Oxygen

Prokaryotic MetabolismProkaryotic Metabolism

Can use alcohol fermentation pathway or Can use alcohol fermentation pathway or lactate (lactic acid fermentation pathway).lactate (lactic acid fermentation pathway).

In cheese making, we used the lactic acid In cheese making, we used the lactic acid pathway using bacteria pathway using bacteria LactobacillusLactobacillus..

First, proteins in milk are transformed into First, proteins in milk are transformed into solid lumps called curds. Second, the curds solid lumps called curds. Second, the curds are separated from the milky liquid, called are separated from the milky liquid, called whey, and shaped or pressed into molds. whey, and shaped or pressed into molds. Finally, the shaped curds are ripened using a Finally, the shaped curds are ripened using a variety of different aging and curing variety of different aging and curing techniques. techniques.

Your JobYour Job

What is happening with rising What is happening with rising bread? Which pathway and what bread? Which pathway and what happens to all these products?happens to all these products?

What other foods do we make or What other foods do we make or utilize using microbes?utilize using microbes?