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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
how is sake made?
performing amylolytic fermentation on cooked rice, which will turn the rice into a simple syrup in approx. a day, followed by alcoholic fermentation
26
What is proteolytic fermentation?
the use of molds on high protein foods in order to ferment
27
is a starter culture requires for proteolytic fermentation?
yes
28
what is an example of proteolytic fermentation
the use of penicillium to disest proteins which makes a runnier cheese with very complex flavors
29
another example of Proteolytic fermentation?
Tempeh; rhizopus oryzae is used to ferment soybeans into a kind of pancake
30
what is acetic acid?
Ch3CO2H, also known as vinegar
31
what is glacial acetic acid?
acetic acid that is water free
32
what are two ways acetic acid can be produced?
synthetically, or by bacterial fermentation (the biological route)
33
how would you categorize acetic acid bacteria?
gram-negative bacteria that carry out oxidative fermentation to produce acetic acid from ethanol in a fermentation process
34
when are acetic acid bacteria not considered acetic acid bacteria
when they produce acetic acid via anaerobic fermentation
35
what is the oxidative fermentation reaction?
acetobacter performing the conversion of ethanol into acetic acid using oxygen as an oxidizer
36
what are common sources of ethanol?
hard apple cider, wine, and fermented grain, salt, rice, or potato mashes
37
what's the physical process of oxidative fermentation?
a dilute solution being inoculated with acetobacter and kept in a warm place for a few months
38
how is industrial vinegar produced in an efficient way?
plants providing a large supply of oxygen to bacteria
39
Anaerobic fermentation of acetic acid
conversion of sugar into acetic acid without an ethanol intermediate
40
what bacteria use anaerobic fermentation?
Clostridium and Acetobacterium
41
definition of acetogenic
bacteria that produce acetic acid anaerobically
42
what compounds do acetogenic bacteria use to produce acetic acid?
carbon dioxide or methanol, and hydrogen
43
is acetobacter tolerant to high levels of acidity?
yes
44
acetobacter
produces acetic acid/vinegar using oxidative fermentation
45
how many genera are there of AAB?
17
46
important genera of AAB
Acetobacter, Gluconobacter, Gluconoacetobacter, and Komagataeibacter
47
What phylum are AAB under?
Proteobacteria
48
what class are AAB under?
Alphaproteobacteria
49
what order are AAB under?
Rhodospirillales
50
what family are AAB under?
Acetobacteraceae
51
what kind of environments are AAB usually found in?
environments where there are high concentrations of sugar, alcohols, or sugar alcohols. highly aerobic environments
52
how is AAB metabolism unique?
Performing oxidative fermentation, AAB oxidize their substrates and then use the accumulated products later on
53
what are sugar-rich niches AAB are found in?
fruits and flowers
54
Sugar Alcohol
organic compounds derived from sugars, a class of polyols
55
how are sugar alcohols commonly used?
used in the food industry as thickeners and sweeteners
56
what group of people benefit from the use of sugar alcohols?
diabetics. sugar alcohols are just as sweet but dont contain all the calories
57
what do AAB oxidize as obligate aerobes?
ethanol, sugars, and sugar alcohols to produce sugar acids
58
what is the byproduct of oxidative fermentation?
water
59
what is the first step in the biochemistry of oxidative fermentation?
starts in the periplasm, AAB partially oxidize ethanol by alcohol dehydrogenase and aldehyde dehydrogenase
60
second step of oxidative fermentation?
AcOH accumulates in the media
61
third step of oxidative fermentation?
membrane bound ADH and ALDH transfers electrons via ubiquinone and terminal ubiquinol oxidase to oxygen as the final electron acceptor
62
what other cycle can oxidative fermentation feed?
the TCA cycle
63
what is overoxidation?
when strains oxidize acetic acid
64
what kind of growth curve does overoxidation create?
a biphasic growth curve
65
what kind of growth curve is shown when the initial ethanol concentration of below 1%?
diauxic growth curve
66
what are the three phases of the diauxic growth curve in AAB fermentation?
1. Log phase 2. Transition phase 3. Overoxidation phase
67
what bacterial strains of AAB oxidize acetic acid via the TCA cycle?
Acetobacter and Gluconacetobacter
68
what bacterial strain of AAB cannot oxidize acetic acid via the TCA cycle?
Gluconobacter; They do not have a function TCA cycle do to lack of key enzymes
69
what type of other acid aside from AAB can be oxidized via the TCA cycle?
Lactic Acid; oxidized to acetoin which smells like butter in spoiled wine
70
What are the two types of Acetic Acid Fermentation?
1. Surface Static Processes | 2. Submerged Processes
71
Surface Static Process
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
Submerged process
use of Komagataeibacter strains, reaching acidity levels of 15-20%. involves rapid mixing with forced aeration in a bioreactor
73
is acetic acid a weak or strong acid?
weak lipophilic acid that can readily diffuse through the cytoplasmic membrane
74
why can AAB kill bacteria even in acidic concentrations as low as 0.5%?
diffuse through the membrane bringing the H atom with them which increases intracellular acidity
75
what can lower pH in the cell cause?
protein mis-folding
76
what are the four mechanisms for AAB resistance to acetic acid?
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
What are General Stress Proteins?
molecular chaperones
78
What are the stressors in oxidative fermentation of AAB?
ethanol and acetic acid
79
what is the function of molecular chaperones?
1. prevent denatured proteins from aggregating 2. resolubilize aggregated proteins 3. facilitating the degradation of seriously damaged proteins
80
what are the two molecular chaperones found in bacterial cells?
1. GroES-GroEL 2. DnaK-DNAJ-Grp
81
What is GroES-GroEL?
a chaperone representative of heat shock proteins found in all bacteria
82
What is the function of GroES-GroEL?
prevents the aggregation of denatured proteins
83
what does GroEL form?
the heptamer ring structure
84
what does GroES form?
the heptamer lid-like structure
85
when is GroES-GroEL activated?
when AAB are exposed to ethanol or acetic acid
86
What is the function of DnaK-DnaJ-GrpE?
folds nascent proteins, refold denatured proteins, and degrades seriously denatured proteins
87
DnaJ:
binds to improperly folded proteins and targets them to DnaK
88
DnaK:
places the protein in a cleft when in an open conformation
89
GrpE:
release proteins from DnaK by removing the ADP from it and providing it with an ATP
90
When is DnaK-DnaJ-GrpE activated?
in the presence of ethanol, not acetic acid

FDSC 442 (13 decks)

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