12. Microbial Metabolism

Which of the following reactions is undesirable in winemaking?

a. Sucrose → ethanol

b. Ethanol → acetic acid

c. Malic acid → lactic acid

d. Glucose →pyruvic acid

Match the term to the statement (some statements may be used more than once; others may not be used at all).

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Indicate which statements about fermentation are true, and then correct the false statements.

a. Fermentation is an anaerobic process that can be used by prokaryotic or eukaryotic cells.

b. Sugars are the only nutrients that can be fermented.

c. Fermentation is a low ATP yielding process.

d. There are only five types of fermentation: homolactic, heterolactic, alcohol, mixed acid, and butanediol fermentation.

e. Fermentation is the same as anaerobic respiration.

Draw and then fill out a Venn diagram (see sample version here) that compares and contrasts anaerobic respiration to aerobic respiration. The middle section of the diagram is where you should list the features these processes have in common. Include as many details as possible in this diagram to make this a useful exercise.

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The photo shows an organism growing in glucose fermentation broth. What can you conclude about this specimen with regard to its ability (or lack thereof) to ferment the sugar sucrose? Explain your answer.

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Under ideal conditions, the fermentation of one glucose molecule by a bacterium allows a net gain of how many ATP molecules?

a. 2

b. 4

c. 38

d. 0

Anaerobic respiration typically uses (organic/inorganic)________ molecules as final electron acceptors.

How does oxidation of a molecule occur without oxygen?

What happens to the carbon atoms in sugar catabolized by Escherichia coli?

How do yeast cells make alcohol and cause bread to rise?

Commercially produced beers and wines are usually fermented with the aid of _______.

a. naturally occurring bacteria

b. naturally occurring yeast

c. specific cultured bacteria

d. specific cultured yeast

Which of the following would be the best growth medium to use for industrial fermentations?

a. corn

b. synthetic medium made by hand

c. whey from cheese production

d. brewing mash

Industrial fermentation _________.

a. always involves alcohol production

b. involves the large-scale production of any beneficial compound

c. refers to the oxidation of sugars using organic electron acceptors

d. is any desirable change to food by microbial metabolism

Indicate whether each of the following statements is true or false. Rewrite the underlined phrase to make a false statement true.

______The fermentation of dairy products relies on mixed acid fermentation.

Indicate whether each of the following statements is true or false. Rewrite the underlined phrase to make a false statement true.

______Sauerkraut production involves the alcoholic fermentation of cabbage.