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FDSC 442 > Acetic acid bacteria > Flashcards

Acetic acid bacteria Flashcards

1
Q

how was milk initially preserved?

A

by producing cheese

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2
Q

what was the first disease sauerkraut saved the brits from?

A

scurvy

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3
Q

benefits of fermenting foods

A
  1. improve organoprofile
  2. shelf life extended
  3. availability of nutrients is improved
  4. potential health-promoting properties (prevention of scurvy)
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4
Q

Spontaneous fermentation

A

fermentation naturally occurring from the action of wild microbes. Growth encouraged by simply just creating the optimal environment for bacterial growth, i.e., anaerobic or aerobic

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5
Q

Inoculated fermentation

A

use of starter cultures that are required to start the process of fermentation, as well as creating the optimal environment necessary

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6
Q

advantage of inoculated fermentation

A

stabilizes fermentations that are sensitive to contamination
ex ) Wine

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7
Q

Back slopping

A

using an already fermented product, to start a new reaction of fermentation

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8
Q

Different types of fermentation

A
  1. Acetic
  2. Lactic
  3. Alcoholic
  4. Proteolytic
  5. Amylolytic
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9
Q

Who performs Acetic fermentation

A

acetic acid bacteria

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10
Q

what products does acetic fermentation create?

A

kombucha, apple cider vinegar

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11
Q

is acetic fermentation anaerobic or aerobic?

A

aerobic, oxygen and alcohol must both be present. alcohol is being oxidized (the reagent)

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12
Q

what does contamination of AAB result in?

A

conversion of wine, beer, cider, or any alcoholic beverage, into vinegar

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13
Q

how is kombucha made?

A

yeasts and bacteria work together to make alcohol (by using sugar) and convert it into vinegar, done by AAB

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14
Q

what is Lactic fermentation

A

fermentation is done by LAB, bacteria that utilize sugars to produce lactic acid, increasing acidity

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15
Q

what is lactic fermentation mainly used for?

A

fermentation of vegetables, meat, and milk

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16
Q

example of meat that is fermented

A

cured meat

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17
Q

example of vegetables that are fermented

A

cabbage into saurkraut, kimchi, pickles, capers, miso

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18
Q

examples of milk fermentation

A

yogurt, kefir, cheese

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19
Q

do you need a starter culture for vegetable fermentation?

A

no, you just need to create favorable conditions

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20
Q

are starter cultures used in dairy fermentations?

A

yes because it is hard for LAB to overcome other bacteria present in dairy

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21
Q

What is alcoholic fermentation?

A

the use of pure yeast to convert sugar to alcohol

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22
Q

what kind of environment must alcoholic fermentation be carried out in?

A

anaerobic

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23
Q

What is Amylolytic fermentation?

A

the use of molds to convert complex carbohydrates such as starch, into simple sugars. The use of simple sugars can then be used to produce alcohol

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24
Q

Where is amylolytic fermentation most common?

A

Asia, where it can be used to make koji and nuruk

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25
Q

how is sake made?

A

performing amylolytic fermentation on cooked rice, which will turn the rice into a simple syrup in approx. a day, followed by alcoholic fermentation

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26
Q

What is proteolytic fermentation?

A

the use of molds on high protein foods in order to ferment

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27
Q

is a starter culture requires for proteolytic fermentation?

A

yes

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28
Q

what is an example of proteolytic fermentation

A

the use of penicillium to disest proteins which makes a runnier cheese with very complex flavors

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29
Q

another example of Proteolytic fermentation?

A

Tempeh; rhizopus oryzae is used to ferment soybeans into a kind of pancake

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30
Q

what is acetic acid?

A

Ch3CO2H, also known as vinegar

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31
Q

what is glacial acetic acid?

A

acetic acid that is water free

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32
Q

what are two ways acetic acid can be produced?

A

synthetically, or by bacterial fermentation (the biological route)

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33
Q

how would you categorize acetic acid bacteria?

A

gram-negative bacteria that carry out oxidative fermentation to produce acetic acid from ethanol in a fermentation process

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34
Q

when are acetic acid bacteria not considered acetic acid bacteria

A

when they produce acetic acid via anaerobic fermentation

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35
Q

what is the oxidative fermentation reaction?

A

acetobacter performing the conversion of ethanol into acetic acid using oxygen as an oxidizer

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36
Q

what are common sources of ethanol?

A

hard apple cider, wine, and fermented grain, salt, rice, or potato mashes

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37
Q

what’s the physical process of oxidative fermentation?

A

a dilute solution being inoculated with acetobacter and kept in a warm place for a few months

38
Q

how is industrial vinegar produced in an efficient way?

A

plants providing a large supply of oxygen to bacteria

39
Q

Anaerobic fermentation of acetic acid

A

conversion of sugar into acetic acid without an ethanol intermediate

40
Q

what bacteria use anaerobic fermentation?

A

Clostridium and Acetobacterium

41
Q

definition of acetogenic

A

bacteria that produce acetic acid anaerobically

42
Q

what compounds do acetogenic bacteria use to produce acetic acid?

A

carbon dioxide or methanol, and hydrogen

43
Q

is acetobacter tolerant to high levels of acidity?

A

yes

44
Q

acetobacter

A

produces acetic acid/vinegar using oxidative fermentation

45
Q

how many genera are there of AAB?

A

17

46
Q

important genera of AAB

A

Acetobacter, Gluconobacter, Gluconoacetobacter, and Komagataeibacter

47
Q

What phylum are AAB under?

A

Proteobacteria

48
Q

what class are AAB under?

A

Alphaproteobacteria

49
Q

what order are AAB under?

A

Rhodospirillales

50
Q

what family are AAB under?

A

Acetobacteraceae

51
Q

what kind of environments are AAB usually found in?

A

environments where there are high concentrations of sugar, alcohols, or sugar alcohols. highly aerobic environments

52
Q

how is AAB metabolism unique?

A

Performing oxidative fermentation, AAB oxidize their substrates and then use the accumulated products later on

53
Q

what are sugar-rich niches AAB are found in?

A

fruits and flowers

54
Q

Sugar Alcohol

A

organic compounds derived from sugars, a class of polyols

55
Q

how are sugar alcohols commonly used?

A

used in the food industry as thickeners and sweeteners

56
Q

what group of people benefit from the use of sugar alcohols?

A

diabetics. sugar alcohols are just as sweet but dont contain all the calories

57
Q

what do AAB oxidize as obligate aerobes?

A

ethanol, sugars, and sugar alcohols to produce sugar acids

58
Q

what is the byproduct of oxidative fermentation?

A

water

59
Q

what is the first step in the biochemistry of oxidative fermentation?

A

starts in the periplasm, AAB partially oxidize ethanol by alcohol dehydrogenase and aldehyde dehydrogenase

60
Q

second step of oxidative fermentation?

A

AcOH accumulates in the media

61
Q

third step of oxidative fermentation?

A

membrane bound ADH and ALDH transfers electrons via ubiquinone and terminal ubiquinol oxidase to oxygen as the final electron acceptor

62
Q

what other cycle can oxidative fermentation feed?

A

the TCA cycle

63
Q

what is overoxidation?

A

when strains oxidize acetic acid

64
Q

what kind of growth curve does overoxidation create?

A

a biphasic growth curve

65
Q

what kind of growth curve is shown when the initial ethanol concentration of below 1%?

A

diauxic growth curve

66
Q

what are the three phases of the diauxic growth curve in AAB fermentation?

A
  1. Log phase
  2. Transition phase
  3. Overoxidation phase
67
Q

what bacterial strains of AAB oxidize acetic acid via the TCA cycle?

A

Acetobacter and Gluconacetobacter

68
Q

what bacterial strain of AAB cannot oxidize acetic acid via the TCA cycle?

A

Gluconobacter; They do not have a function TCA cycle do to lack of key enzymes

69
Q

what type of other acid aside from AAB can be oxidized via the TCA cycle?

A

Lactic Acid; oxidized to acetoin which smells like butter in spoiled wine

70
Q

What are the two types of Acetic Acid Fermentation?

A
  1. Surface Static Processes

2. Submerged Processes

71
Q

Surface Static Process

A

use of Acetobacter to form a thin film on the surface of growth media, which becomes thicker over time. Bacteria embedded in the film

72
Q

Submerged process

A

use of Komagataeibacter strains, reaching acidity levels of 15-20%. involves rapid mixing with forced aeration in a bioreactor

73
Q

is acetic acid a weak or strong acid?

A

weak lipophilic acid that can readily diffuse through the cytoplasmic membrane

74
Q

why can AAB kill bacteria even in acidic concentrations as low as 0.5%?

A

diffuse through the membrane bringing the H atom with them which increases intracellular acidity

75
Q

what can lower pH in the cell cause?

A

protein mis-folding

76
Q

what are the four mechanisms for AAB resistance to acetic acid?

A
  1. prevention of acetic acid influx into the cell
  2. acetic acid assimilation
  3. acetic acid efflux (efflux pumps)
  4. Protection of cytoplasmic proteins against denaturing (general stress proteins)
77
Q

What are General Stress Proteins?

A

molecular chaperones

78
Q

What are the stressors in oxidative fermentation of AAB?

A

ethanol and acetic acid

79
Q

what is the function of molecular chaperones?

A
  1. prevent denatured proteins from aggregating
  2. resolubilize aggregated proteins
  3. facilitating the degradation of seriously damaged proteins
80
Q

what are the two molecular chaperones found in bacterial cells?

A
  1. GroES-GroEL 2. DnaK-DNAJ-Grp
81
Q

What is GroES-GroEL?

A

a chaperone representative of heat shock proteins found in all bacteria

82
Q

What is the function of GroES-GroEL?

A

prevents the aggregation of denatured proteins

83
Q

what does GroEL form?

A

the heptamer ring structure

84
Q

what does GroES form?

A

the heptamer lid-like structure

85
Q

when is GroES-GroEL activated?

A

when AAB are exposed to ethanol or acetic acid

86
Q

What is the function of DnaK-DnaJ-GrpE?

A

folds nascent proteins, refold denatured proteins, and degrades seriously denatured proteins

87
Q

DnaJ:

A

binds to improperly folded proteins and targets them to DnaK

88
Q

DnaK:

A

places the protein in a cleft when in an open conformation

89
Q

GrpE:

A

release proteins from DnaK by removing the ADP from it and providing it with an ATP

90
Q

When is DnaK-DnaJ-GrpE activated?

A

in the presence of ethanol, not acetic acid

FDSC 442 (13 decks)

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