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Food Fermentation Technology > 6. Fermentation System and Fermentor > Flashcards

6. Fermentation System and Fermentor Flashcards

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1
Q

Four major groups of fermentation processes

A
  1. produce microbial cells/biomass
  2. produce microbial enzymes
  3. produce microbial metabolites
  4. those that modify compounds added to fermentation/present in media or substrate
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2
Q

What is submerged fermentation

A

Involves submersion of the microorganism in an aqueous solution with all nutrients required for growth

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3
Q

Submerged fermentation done in what tool/apparatus

A

bench scale in flask/bottle or bench fermentor

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4
Q

Submerged liquid fermentation normally done for what

A

production of microbially derived enzymes

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5
Q

Examples of food product utilizing submerged liquid fermentation

A

yogurt, citric acid, extracellular enzymes

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6
Q

volume of industrial scale fermentor

A

up to 1000m^3

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7
Q

advantage of submerged fermentation

A
  • suitable for bacteria that req high aw
  • higher purity obtained
  • even distribution of yeast and bacteria
  • controlling and measuring parameters is simpler that solid state fermentation
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8
Q

disadvantage of submerged fermentation

A
  • expensive, high cost of media
  • low volumetric productivity
  • more efflux generated
  • ineffective oxygen circulation
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9
Q

principles of solid state fermentation

A
  • production of bioproducts from microbes that req low aw for growth
  • microbe growth on surface of solid substrate
  • majority of water absorbed within moist solid particles
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10
Q

examples of solid substrate in solid state fermentation

A

rice bran, wheat bran, grain

REQUIRES NO PROCESSINg

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11
Q

Advantages of solid state fermentation

A
  • simple natural solids as media, can utilize agro-industrial residues
  • low technology, low energy expenditure, less capital investment
  • reasonably high yield
  • bioreactor design, aeration process, effluent treatment are simple
  • higher volumetric productivity
  • resembles natural habitat of fungi and bacteria
  • easier downstream processing
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12
Q

disadvantages of solid state fermentation

A
  • only microbes that can tolerate low aw can be used
  • precise monitoring (eg of O2, CO2 levels, mc) is not possible
  • organisms grow slowly and consequently, limitation in product formation
  • heat production creates problems difficult to regulate growth environment
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13
Q

Types of fermentation operations

A
  • batch
  • fed batch
  • continuous
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14
Q

what type of fermentation operation for submerged

A

batch, fed batch, continuous

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15
Q

what type of fermentation operation for SSF

A

batch

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16
Q

principles of batch fermentation

A
  • sterile medium in a vessel inoculated with starter culture
  • fermentation proceeds without addition of fresh growth medium
  • substrate concentration declines as cell number increased
17
Q

characteristics of batch fermentation

A
  • closed system
  • well mixed
  • constant volume
18
Q

principles of fed batch fermentation

A
  • LENGTHEN LOG PHASE
  • nutrients added at intervals
  • no growth medium removed
  • substrate concentration maintained at constant
  • growth curve similar to batch
19
Q

how to keep culture in log phase?

A

MAX GROWTH RATE
- feed in nutrients
- remove cells and wastes
- maintain physical environment
-> CONTINUOUS SYSTEM

20
Q

principles of continuous fermentation

A

fresh growth medium is added and spent medium removed continuously AT SAME FLOW RATE AS FERMENTATION BROTH LEAVING SYSTEM

  • cell number and growth limiting substrate is maintained throughout fermentation time
  • can last up to 1000 hours
21
Q

principles of multistage system fermentation

A
  • different condition prevail in separate stage
  • advantageous in the utilization of multiple carbon sources or multiple culture, and in the production of secondary metabolites
22
Q

example of multistage continuous fermentation

A
  • glucose > ethabol > acetic acid
  • glucose > ethanol (S. cerevisiae)
  • ethanol > acetic acid (Gluconobacter)
23
Q

Characteristics of growth associated products

A

produced DURING TROPOPHASE (simultaneously with growth (exp), then decline)

product formation affected by growth rate (directly proportional)

24
Q

Characteristics of non-growth associated products

A

produced during IDIOPHASE (stationary)
- other secondary metabolites such as toxin
- eg antibiotics, citric acid

25
Q

Characteristics of mixed-growth associated products

A

produced during tropophase, continued during idiophase
- e.g. lactic acid, xanthan gum

26
Q

How does temperature affect product formation

A

temp optimum for growth NOT NECESSARILY optimum for product formation

27
Q

How does pH affect product formation

A
  • H+ conc affects enzyme activity, thus growth rate
  • optimum for growth =/= prod formation (for product associated growth, pH opt for growth = prod formation)
  • most cells can regulate intracellular pH in the presence of fluctuations in external pH
28
Q

How does dissolved O2 affect product formation

A
  • limiting in aerobic cultivation as it is sparingly soluble in water
  • salts alter solubility
  • high temp decreases solubility

for aerobic culture:
- growth rates varies linearly with dissolved o2 xonc

29
Q

how to overcome O2 limitation

A
  • sparging reactor continuously
  • sparging O2 with enriched air
  • adding H2O2 and catalase
  • working under higher pressure (1-2 atm)
30
Q

How does dissolved CO2 affect product formation

A
  • affect performance of cells
  • high conc may be toxic
  • some CO2 req for metabolic functions
  • controller by changing amount in air supply/change agitation speed
31
Q

How does dissolved CO2 affect product formation

A
  • affect performance of cells
  • high conc may be toxic
  • some CO2 req for metabolic functions
  • controller by changing amount in air supply/change agitation speed
32
Q

CONTINUE AT P21

A

Food Fermentation Technology (4 decks)

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