K.K Lecture 1&2

Question 1

What does fermentation produce?

Answer 1

Primary Metabolite, secondary metabolite, enzymes & lipases etc.

Question 2

Primary Metabolite

Answer 2

Actively growing cells. e.g Acetic Acid

Question 3

Secondary Metabolite

Answer 3

E.g antibiotics. Produced when cells stop growing

Question 4

What does the choice of fermentation system depend on?

Answer 4

*The Cell type
*The type of product required
*The scale production

Question 5

Name the fermentation systems

Answer 5

1.Solid Fermentations
2.Film Fermentations
3.Batch Fermentation
4.Fed Batch
5.Cell Recycle Batch Fermentation
6.Continuous Fermentation

Question 6

What is Solid Fermentation?

Answer 6

*Fungus grows on a soild substrate in the absence of free water.
*Fungus must be able to tolerate low water activity

Question 7

Examples of Solid Fermentation Products

Answer 7

*Mushroom Production - Straw/Manure- Agaricus bisporus

*Compost Production - A combination of yeast (Candida lipolytica) filamentous is used to degrade straw to produce fungal biomass

*Soy Sauce - Soy Beans - Aspergillus oryzae.

Question 8

Explain the Symbra Process

Answer 8

*This is an example of solid fermentation

*Uses a single fungal species or mixture to convert straw into a fungal biomass which animals can eat.

1. Candida lipolytica - Yeast introduced which breaks down lipids
2. Chaetomium cellulolyticum - fungi which breaks down carbs or cellulose

Question 9

What is Film Fermentation?

Answer 9

*Fermentation occurs in layer/film
*Fungus grows on the surface
*As it grows it secretes metabolites into the medium during the liquid phase.

Question 10

Examples of Film Fermentation

Answer 10

*Waste Water Treatment
*Sludge Treatment
*Antibiotic Production

Question 11

What is Batch Fermentation Used for?

Answer 11

*Most Commonly Used system
*Used for antibiotics
*Used for the production of solvents such as ethanol and acetone

Question 12

Name the stages of the Growth Curve (Batch Fermentation)

Answer 12

1. Lag Phase
2. Accerelation Phase
3. Exponential Phase
4. Deceleration Phase
5. Stationary Phase
6. Death Phase

Question 13

Lag Phase

Answer 13

*Cells adapting to environment: Nutrient, pH, Temperature
*Intense Biochemical Activity - & Synthesis of Enzymes

Question 14

Exponential Phase

Answer 14

*Is accompanied by maximal utilisation of nutrients.
*Unlimited Growth, No inhibitors, High nutrients, Initially Low cell Number

Question 15

4. Deceleration Phase

Answer 15

Growth Slows Down
– Nutrient Levels Drop
– Increased Levels of Inhibitors
– Alterations in pH

Question 16

5. Stationary Phase

Answer 16

No overall increase in Numbers
Nutrient Depletion
High Levels of Inhibitors
Rate of Growth = Rate of Death

Question 17

6. Death Phase

Answer 17

Cell Lysis
Spore Formation
Viable But Non-Culturable (VBNC) State

Question 18

Biphasic Growth

Answer 18

Continuation of the fermentation will ultimately result in depletion of the ethanol as this is consumed by the yeast in the absence of the original carbohydrates. The culture will consequently display a biphasic growth curve.

Question 19

4. Fed-Batch Fermentation

Answer 19

*Fed-batch is very similar to batch fermentation except nutrients are added periodically during the fermentation process to stimulate growth

*No withdrawal from fermentation

*Optimal for maximising biomass

*Employed for the production of Baker’s yeast

Question 20

Is Fed-Batch fermentation suitable for the production of ethanol?

Answer 20

No, as it favors growth over ethanol production

Question 21

5. Cell Recycle Batch Fermentation (Melle-Boinot Process)

Answer 21

*Cell mass at the end of one batch is used to inoculate the next fermentation thus inducing a high cell density

*More energy is available for biomass production due to high cell density

*Increased amount of end product

*Hold culture in Stat. Phase

*Optimise parameters for Max. production

*May be strain/species/substrate specific

Question 22

6. Continuous Fermentation

Answer 22

*In this system cells are grown under steady-state conditions and maintained at a particular stage of their growth cycle.

*Nutrients are added at a constant rate and biomass or spent medium is removed at the same rate in order to maintain a constant reaction volume.

*Regulate, pH, nutrients and monitor effects

Question 23

Factors Affecting Fermentation Productivity

Answer 23

1. Type of Fermentation System
2. Nature of Fungus
3. Medium
4. Temperature
5. pH
6. Aeration
7. Agitation - Break Mycelial Forms
8. Moisture Content

Question 24

Nature of Fungus

Answer 24

A. SINGLE CELL (YEAST)
ADHERENT/ANCHORAGE DEPENDENT
MYCELIAL FORM (PENICILLIUM)
B. AEROBIC / SEMI-AEROBIC / ANAEROBIC
C. SPECIAL REQUIREMENTS (INOCULUM)
D. END PRODUCT TOLERANCE