Fermentation

Question 1

Define fermentation

Answer 1

• anaerobic catabolism of organic compound which serves as electron donor and acceptor

Question 2

Anaerobic prokaryotes re-oxidize ____ by respiration or _______.

Answer 2

• NADH by fermentation

Question 3

What does adding mineral oil do?

Answer 3

• decreases O2 and inhibits growth of aerobic organisms

Question 4

What happens in the absence of an external electron acceptor?

Answer 4

• organic compounds can be catabolized ONLY by fermentation

Question 5

only certain compounds are fermentable, what is required for most fermentations?

Answer 5

• energy-rich organic intermediate formed that can yield ATP by substrate-level phosphorylation
• redox balance

Question 6

What is a means of disposing excess electrons?

Answer 6

• production of H2, associated with presence of iron-sulfur protein ferredoxin

Question 7

What is ferridoxin?

Answer 7

• very low potential electron carrier

Question 8

What is the transfer of electrons from ferredoxin to H2 catalyzed by?

Answer 8

• hydrogenase

Question 9

How do you protect from too much acidity?

Answer 9

• remove electron acceptors

Question 10

What is a key product of many fermentative processes?

Answer 10

• pyruvate

Question 11

What has fermentative metabolism?

Answer 11

• acids and ethanol

Question 12

What puts holes in swiss cheese?

Answer 12

• propionibacterium

Question 13

What are carbohydrate fermentations?

Answer 13

• lactic
• ethanol
• butyric
• mixed acid
• propionic
• homeoacetic

Question 14

What does it mean that there is considerable diversity in fermentation?

Answer 14

• product of one organisms fermentation is fermented by a second organism
• some employ ion gradients as basis for energetics across membrane

Question 15

What happens when inadequate energy is released?

Answer 15

Coupled to ATP synthesis directly by substrate-level phosphorylation

Question 16

What compounds can still support growth of the organism with inadequate energy?

Answer 16

• succinate and oxalate

Question 17

What ferments succinate?

Answer 17

• propionigenium modestrum

Question 18

What does chemiosmotic ATP formation result from?

Answer 18

• Na+ pump (decarboxylation of organic acids)
  -ex. decarboxylation of succinate coupled to export of sodium across cytoplasmic membrane

Question 19

What happens during oxalate decarboxylation?

Answer 19

• decarboxylated to formate = build-up of proton motive force from exportation of formate

Question 20

Explain the anaerobic food chain

Answer 20

• fermentation of amino acids, carbs, purines and pyrimidines to organic acids and alcohols followed by conversion to CO2, H2, and acetate
• methanogens convert compounds to CH4 and CO2

Question 21

What is the fermentation pathway of Clostridium propionicum?

Answer 21

• lactate oxidized to pyruvate
• pyruvate oxidized to acetyl-CoA and CO2
• acetyl-CoA converted to acetate and ATP by acetyl-P
• lactate acquires CoA from propionyl-CoA
• lactyl-CoA dehydrated to acrylyl-CoA –> reduced to propionyl-CoA

Question 22

What is the overall equation for fermentation of clostridium propionicum?

Answer 22

• 2 lactate –> 2 propionate + acetate + CO2 + H2O (3ATP)

Question 23

What is the simplified pathway of fermentation of clostridium propionicum?

Answer 23

• Lactate –> pyruvate = 3 ATP and acetate
• feeds back on self, picks up CoA to generate propionate and CoA transfer

Question 24

How many moles of ATP per molecule of acetate are generated when bacteria are growing on glucose using the EMP pathway?

Answer 24

• 2

Question 25

What does propionate fermentation by the Succinate-propionate pathway yield?

Answer 25

- more ATP than acrylate pathway per mole propionate formed

Question 26

What are the characteristics of propionibacterium?

Answer 26

- G+ve - anaerobic - non-spore forming - non-motile - rod

Question 27

What does acetate fermentation do?

Answer 27

- generates acetate from different starting products - pyruvate feeds central metabolism - generates CO2 and ammonia = feeds other organisms

Question 28

What is syntrophism?

Answer 28

- 2 organisms carry out chemical transformation that neither can complete individually - ex. nitrification (ammonia to nitrite, nitrite to nitrate)

Question 29

What does acetogenesis mean?

Answer 29

- generation of acetate

Question 30

What does homofermentative mean?

Answer 30

- single end product

Question 31

What does heterofermentative mean?

Answer 31

- multiple end products

Question 32

what ferments glucose to lactate? what is it used as?

Answer 32

- heterogenous group of anaerobes - only or major product of fermentation

Question 33

What does aerotolerant mean?

Answer 33

- can tolerate presence of oxygen but not adapted to utilize it

Question 34

What makes gas during fermentative metabolism in the infant gut? what is better?

Answer 34

- e. coli - bifidobacteria needed in gut

Question 35

What are the products of mixed acid fermentation?

Answer 35

- succinate, lactate, acetate, ethanol, formate, CO2, H+

Question 36

What are enteric bacteria? give 3 examples

Answer 36

- facultative anaerobes - e. coli., salmonella, shigella

Question 37

State and briefly describe 3 reasons why some microorganisms may use fermentative metabolism. Name 2 environmental niches where you may expect to find fermentative bacteria.

Answer 37

- May be the only way they can attack or utilize nutrients -Environmental condition (no O2) - Absence of external electron acceptor (O2), organic compounds can only be catabolized by fermentation - Less energy produced but supports growth - Too much competition - Not enough resources for nutrition and survival any other way - Nature of compound - Easy for microorganism to utilize than others, some cannot be attacked Niches : gut of cow, wetland soil (ANOXIC AND DEVOID OF OXYGEN)