12. Microbial Metabolism

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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Food fermentations do all of the following except ________.

a. Give foods a characteristic taste

b. Lower the risk of food spoilage

c. Sterilize foods

d. Increase the shelf life of the food

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

Use the following choices to answer the question.

a. E. coli growing in glucose broth at 35℃ with O₂ for 5 days

b. E. coli growing in glucose broth at 35℃ without O₂ for 5 days

c. Both a and b

d. Neither a nor b

Which culture produces the most lactic acid?

Match each term with its correct definition.

1._______ Organisms whose presence in water indicates contamination from feces

2._______Refers to water that is fit to drink

3._______Used in the processing of animal wastes; mimics primary and secondary wastewater treatment

4._______Water that is not bound by solutes

5._______Undesirable fermentation reactions in food, leading to poor taste, smell, or appearance

6._______Brief heating of foods during processing

7._______Descriptor of the level of organic material present in wastewater

8._______Fermentative products produced by microorganisms during stationary phase

A. Spoilage

B. Water activity

C. Coliforms

D. Pasteurization

E. Secondary metabolites

F. Potable

G. BOD

H. Oxidation lagoon

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

How does oxidation of a molecule occur without oxygen?

Describe an example of bioconversion. What metabolic processes can result in fuels?

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

______ The fermentation of dairy products relies on mixed acid fermentation.

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

Which of the following statements about NAD⁺ is true?

a) NAD⁺ is reduced to NADH during glycolysis, pyruvate oxidation, and the Krebs cycle.

b) NAD⁺ has more chemical energy than NADH.

c) NAD⁺ donates high energy electrons to the electron transport chain.

d) In the absence of NAD⁺, glycolysis can still function.