Commercial Applications of Biotechnology
Batch and continuous culture -
- Microorganism started population is mixed with a specific quantity of nutrient solution then allowed to grow for a certain amount of time with no extra nutrients added.
- At end, products removed and fermenation tank is emptied. eg Penicilin
- Growth rate is slower as nutrient levels decline over time, easy to set up and make, if contaminated only one batch is lost, less efficent as fermenter is not in use all the time, useful for producing secondary metabolites.
- Nutrients and its products are removed from the tank at seperate intervals. eg human hormone Insulin
- Growth rate is higher as nutrients are not used up, setting up is more difficult as growing conditions are hard to achieve, if contamination occurs large volumes are lost, more efficent as fermenter is working constantly, useful for producing primary metabolites.
Commercial Applications of Biotechnology
Aspesis is vital in biotechnological proccesses involving organisms - contaminants are unwanted microorganisms that can interfere with production, they:
- Compete with culture for space and nutrients
- Reduce yeild of useful products from the cukture
- may cause spoilage of the product or produce toxic chemicals
Aseptic techniques are used to ensure asepsis.
Aseptic tecniques at lab level - sterilisation of equptment and near by areas before and after use; heating with flame, UV light or disinfectant sprays.
Aseptic techniques art large scale culture level - Washing, disinfecting and steam cleaning the fermemter between each use kills microorganisms. Polished stainless steel used to stop microorganisms sticking well to its surface. Steralising nutrient mediums before use to stop contaminates being introduced. Fine filters entering and exiting the vessel aviod microorganisms entering.
Enzymes are powerful catalysts -
- specificity - enzymes can catalyse reactions that are specific to their tertiary structure and active site. Fewer by-products are produced and less purification of the products is required.
- temperature of enzyme reaction - function at much lower temperatures than chemical processes or they denature. This enables fewer fuel costs.
- It is often more efficient to used isolated enzymes to carry out the reaction rather than growing the whole organism using an inorganic catalyst.
- Isolated enzymes can be produced on a large scale and this extraction from the fermentation mixture is known as downstream processing.
Immobilising enzymes - they can catalyse the reaction without becoming mixed in with the substrate as they would naturally. Advantages of immobilised enzymes: Purification costs are low, enzymes are immediately ready for re-use, they are more stable as the matrix surrounding them protects the enzyme molecule. Disadvantages of immobilised enzymes: Setting the immobilisation up is more expensive, they can be less active as they are not free to mix with substrate and contamination is more expensive as whole system would need to be stopped.
Methods for immobilising enzymes -
- Adsorbtion - Enzymes mixed with immobilising support and attach by hydrophic interactions and ionic links; glass beads, resins etc.
- These interactions are not very strong the enzyme has to be held so the active site is not changed and is displayed giving high reaction rates.
- Covalent Bonding - Enzyme molecules are covalently bonded to an insoluble material (clay) using a cross linking agent like glutaldehyde. This does not hold a large quaintity of enzymes but enzymes are held strongly on support.
- Entrapment - Enzymes are trapped in network of fibres or in a gel bead. They are trapped in their natural state.
- Reaction rates are slower as molecules have to go through the trapping barrier thus active site not as available as covalently bonded enzymes.
- Membrane seperation - Enzymes can be seperated from a mixture using a partially permeable membrane. Enzyme solution is held on one side of the membrane and the substrate solution is held on the other.
- Substrate molecules move so a reaction can take place and then products pass back through the membrane.
Producing new antibiotics is high in demand and to do this immobilised penicillin enzymes to produce a range of different penicillin type antibiotics that targer microorganisms are not resistant to.