- The industrial use of living organisms (or parts of living organisms) to produce food, drugs or other products.
Many biotechnological processes make use of microorganisms (bacteria and fungi) as they have many advantages:
- Rapid growth in favourable conditions.
- Proteins and chemicals produced can be harvested.
- Can be genetically engineered to produce specific products.
- Grows well at low temperatures – lower than those chemical processes.
- Can be grown anywhere – not climate-dependent.
- Purer products than those produced in chemical processes.
- Can be grown using nutrient materials that are useless or toxic to humans.
- A culture is a growth of microorganisms.
- A pure culture contains one microorganism and a mixed culture contains multiple species.
1. Lag phase
- Organisms are adjusting to surroundings (taking in water, cell expansion, activating specific genes, synthesising specific enzymes.
- Cells are active but not reproductive = population remains fairly constant.
2. Log (exponential) phase
- Population size doubles each generation as every individual has enough space and nutrients to reproduce.
3. Stationary phase
- Nutrient levels decrease and waste products and other metabolites build up.
- Rate of death is equal to rate of reproduction.
4. Decline/death phase
- Nutrient exhaustion and increased levels of waste products and metabolites lead to death rate exceeding reproduction rate.
- Eventually, all organisms will die in a closed system.
Immobilisation of Enzymes
- This is where enzymes are held, separated from the reaction mixture.
- Substrate molecules can bind to the enzyme molecules and the products formed go back into the reaction mixture leaving the enzyme molecules in place.
- Methods for immobilising enzymes depend on ease of preparation, cost, relative importance of enzyme ‘leakage’ and efficiency of the particular enzyme that is immobilised.
- Enzyme molecules are mixed with immobilising support and bind to it due to hydrophobic interactions and ionic links.
- Bonding forces are not particularly strong so enzymes can become detached (leakage), however this method can give very high reaction rates.
- Adsorption agents: porous carbon, glass beads, clays and resins.
- Enzymes are covalently bonded to a support, often an insoluble material such as clay particles using a cross-linking agent such as gluteraldehyde and sepharose.
- This method does not immobilise a large quantity of enzyme but binding is very strong so there is very little leakage of enzyme from the support.
- Enzymes are trapped, e.g. in a glass bead or a network or cellulose fibres.
- Reaction rates can be reduced as substrate molecules need to get through the trapping barrier.
- The active site is less easily available than other methods.
- Enzymes are separated from the substrate mixture by a partially permeable membrane.
- The enzyme solution is held at one side of a membrane whilst substrate solution is passed along the other side.
- Substrate molecules are small enough to pass through the membrane to the enzyme.
- Product molecules are small enough to pass back through the membrane.
- In many areas of clinical research and diagnosis and in some industrial processes, the product of a single chemical reaction is required.
- It is often more efficient to use isolated enzymes to carry out the reaction rather than growing the whole organism or using an inorganic catalyst.
- Isolated enzymes can be produced in large quantities in commercial biotechnological processes.
- The extraction of enzyme from the fermentation mixture, involving separation and purification of any product of large-scale fermentations.
The Processes of Continuous Culture and Batch Culture
Industrial-scale fermentations can be operated in two ways:
(1) Batch culture:
- The microorganism is mixed with a specific quantity of nutrient solution.
- It is left to grow for a fixed period with no further nutrient added.
- At the end of the period, the products are removed and the fermentation tank is emptied.
- E.g., pencillin.
(2) Continuous culture:
- Nutrients are added to the fermentation tank.
- Products are removed from the fermentation tank at regular intervals/continuously.
- E.g., insulin.
Drafted by Bonnie (Biology)