Lecture 25

Question 1

Common fermentative breakdown products from catabolizing sugars and fermenting them

Answer 1

alcohols, acids, and CO2 gas

Question 2

final e- acceptor in fermentation is?

Answer 2

some organic molecule (could be pyruvic acid)

Question 3

the process that releases energy from oxidation of organic molecules: examples of these molecules?

Answer 3

this is the definition of fermentation. examples of these organic molecules are sugars, amino acids, organic acids, purines, and pyrimidine

Question 4

keep in mind that microbes are very versatile, the fermentation substrate does not have to be sugars, it can include even unusual compounds like?

Answer 4

aromatics (benzonate), glycerol (sugar-alcohol), acetylene (hydrocarbons).

Question 5

fermentation does not require ______ , but can proceed in the presence of ______ .

Answer 5

oxygen

Question 6

fermentation uses a organic molecule like what as its final electron acceptor?

Answer 6

uses pyruvate or one of its derivatives

Question 7

one of the most important things about fermentation is that it regenerates what? if molecule was only broken down through glycolysis, one would eventually run out of NAD+

Answer 7

NAD+ from NADH

Question 8

fermentation only produces a small amount of ATP

Answer 8

1-2 for each molecule of starting material since many of the energy-rich bonds in the substrate are not broken –> this results in most of the original energy in the substrate remaining in the chemical bonds of organic end products like lactic acid or ethanol

Question 9

fermentation product that has so much stored energy it can be used in gasoline to be combusted/burned to release that energy stored in its chemical bonds

Answer 9

ethanol

Question 10

Many waste products generated from fermentation (many of which can be useful to us, but not necessarily to the microbes), in aerobic respiration the only waste products are _______

Answer 10

CO2 and water

Question 11

two of the most common fermentations of sugars?

Answer 11

lactic acid fermentation, and alcohol fermentation (but even among these two examples, there are many variations of them)

Question 12

Lactic acid bacteria are ________ bacteria that produce LA as a major or sole fermentation product from the fermentation of sugars. Two common examples, and what they can produce?

Answer 12

gram positive nonsporulating bacteria

• two important genera of LA bacteria are the Streptococcus and Lactobacillus
• La fermentation can result in food spoilage, however, it can also produce yogurt from milk, sauerkraut from fresh cabbage, and pickles from cucumbers.

Question 13

In Alcohol fermentation, ______ is released from pyruvic acid to form the intermediate ________, which is quickly reduced to _______ by electrons from NADH. Alcoholic fermentation, although rare in bacteria is common in _______, and is used to make bread and wine.

Answer 13

carbon dioxide is released

form the intermediate acetaldehyde, quickly reduced to ethanol (ethyl alcohol) by electrons from NADH

common in yeasts

Question 14

two types of lactic acid fermentation

Answer 14

homolactic fermentation, and heterolactic fermentation

Question 15

homolactic fermentation

Answer 15

microbes produces lactic acid only

Question 16

heterolactic fermentation

Answer 16

microbes produce lactic acid as well as other acids or alcohols

Question 17

the type of fermentation employed constitutes some degree of compromise between what?

Answer 17

substrate (nutrient) availability, fermentation waste product tolerance, and energy yield

Question 18

what is the most common substrate used for fermentation

Answer 18

sugars

Question 19

typical examples of fermentation products

uncommon examples?

Answer 19

ethanol, lactic acid, lactate, and hydrogen gas (H2), CO2 (yeast)

butyric acid and acetone

Question 20

lactic acid fermentation – steps (pyruvate acts as final e- acceptor here)

Answer 20

first step is the same (glycolysis), and the pyruvate is reduced by NADH to produce lactic acid, and NAD+ is regenerated

Question 21

in solution lactic acid can lose a proton from the acidic group and produce?

Answer 21

the lactate ion CH3CH(OH)COO

Question 22

a type of fermentation test that allows you to test 15 different biochemical reactions in one chamber? what does it help you assess? what change will indicate that your microbe can ferment say for example glucose?

Answer 22

enterotube. you can assess if your microbe is able to ferment a range of different sugars: glucose, lactose, arabinose, sorbitol, adonitol, dulcitol

will be indicated by a color change (say from a pH change to acidic conditions – tells you that your microbe produces acidic end products)

Question 23

ethanol fermentation (remember this happens for each pyruvate molecule – so double products)

Answer 23

same first step glycolysis results in the formation of 2 ATP and 2 NADH

in the second step pyruvate is decarboxylated to acetaldehyde and CO2 is released

acetaldehyde is the final e- acceptor here, and is reduced by one molecule of NADH to form an ethanol molecule (remember there will be two of these)

Question 24

The ethanol and carbon dioxide produced by the yeast _______ are waste products for the yeast, but they are useful to humans. What can these waste products be used for?

Answer 24

Saccharomyces cerevisiae (eukaryote yeast) other strains include Saccharomyces carlsbergensis

ethanol made by yeast used in alcoholic beverages and carbon dioxide made by yeast causes bread dough to rise

Question 25

beer is produced by the fermentation of _______, mainly derived from cereals – the most common of which is _________, although wheat, corn, and rice are also widely used. Most bear is flavored with ______ which adds bitterness (otherwise beer would be sweet). What does hops also help with?

Answer 25

staches, the most common of which is malted barley, flavored with hops

hops also acts as a natural preservative bc it inhibits certain bacteria from growing in it

Question 26

Production of alcohol occurs best in the absence of what? But what does this mean for the yeast?

Answer 26

The production of alcohol occurs best in the absence of oxygen. However, from the yeast's point of view, alcohol and carbon dioxide are waste products, and as the yeast continues to grow and metabolize in the sugar solution, the accumulation of alcohol will become toxic when it reaches a concentration between 14-18%, thereby killing the yeast cells. This is the reason why the percentage of alcohol in wine and beer can only be approximately 16%. In order to
produce beverages (liquor) with higher concentrations of alcohol, the fermented products must be distilled.

Question 27

Wine production using Saccharomyces

Answer 27

Wine can ferment without the addition of sugars, acids, enzymes, or other nutrients. Wine is produced by fermenting crushed grapes using various types of yeast which consume the sugars found in grapes and convert them into alcohol.

Question 28

Lactobacilli used for

Answer 28

yogurt production

Question 29

You can make a bunch of other acids from pyruvic acid – certain acid fermentation pathways will produce

Answer 29

propionic, acetic, butyric, succinic, and formic acid.

Question 30

Other alcohol fermentation reactions will produce

Answer 30

butanol, acetone, isopropyl, etc.

Question 31

Used to ferment starches and maize into both acetone and butanol during WWI for smokeless gunpowder

Answer 31

Clostridium acetabutylicum (this project was carried out by Chaim Weismann)