- the industrial use of living organisms (or parts of living organisms) to produce food, drugs or other products
Why microorganisms are often used in biotechnological processes
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.
Enzymes and other chemicals
- Bio-gas guel production - methanogenic bacteria, grown on concentrated sewage, respire anaerobically and generate gases that can be used as fuel.
- Mycoprotein (Quorn) - Fusarium produces fungal mycelium, which is seperated and processed as food.
- Soya sauce – roasted soya beans are fermented with yeast or fungi such as Aspergillus.
- Penicillin – Penicillium grown in culture produces penicillin as a by-product of its metabolism.
Enzymes and other chemicals
- Water waste treatment – a variety of bacteria and fungi use organic waste in the water as nutrients and make the waste harmless, e.g. Fusarium grown on corn steep liquor, a waste product of the corn milling industry.
Immobilization of enzymes
- 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 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.
Why immobilized enzymes are used in large-scale production
- 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
- Immobilising required additional time, equipment and materials – more expensive.
- Immobilised enzymes can be less active – they do not mix freely with substrate.
- Any contamination is costly – the whole system would need to be stopped.
- 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.
- For example, pencillin.
- Slower growth rate as nutrient level declines with time.
- Less efficient – fermenter is not in operation all of the time.
- Nutrients are added to the fermentation tank.
- Products are removed from the fermentation tank at regular intervals/continuously.
- For example, insulin.
- Faster growth rate as nutrients are continuously added.
- More efficient – fermenter operates continuously.
- Very useful for processes involving the production of primary metabolites.
- More difficult to set up – maintenance of required growing conditions can be difficult to achieve.
- If contamination occurs, huge volumes of product may be lost.
In this IBDP Biology topic, you have to describe the differences between primary and secondary metabolites
- the products of metabolism (the sum of all of the chemical reactions in an organism), e.g. new cells and cellular components, chemicals such as hormones and enzymes, waste products such as carbon dioxide, oxygen, urea, ammonia, nitrates
Primary metabolites – substances produced by an organism as part of its normal growth, e.g. amino acids, proteins, enzymes, nucleic acids, ethanol, lactate. The production of primary metabolites matches the growth in population of the organism.
Secondary metabolites – substances produced by an organism that are not part of its normal growth, e.g. antibiotic chemicals. The production of secondary metabolites usually begins after the main growth period of the organisms – does not match the growth in population of the organism.
Commercial applications of biotechnology
Commercial applications of biotechnology often require the growth of a particular organism on an enormous scale. An industrial-scale fermenter is essentially a huge tank, which may have capacity of tens of thousands of litres. The growing conditions in it can be manipulated and controlled in order to ensure the best possible yield of the product.
The conditions that affect the microorganisms being cultured include:
- Too hot – enzymes will denature and growth will be slowed.
- Too cool – enzymes work less efficiently and growth will be slowed.
2. Type and time of addition of nutrient
- Growth of microorganisms requires a nutrient supply, including sources of carbon, nitrogen and any essential vitamins and minerals.
- The timing of the nutrient addition can be manipulated, depending on whether the process is designed to produce a primary or secondary metabolite.
3. Oxygen concentration
- Most use aerobic conditions, so sufficient oxygen most be available.
- A lack of oxygen leads to the unwanted products of anaerobic respiration and a reduction in growth rate.
- Changes in pH within the fermentation rank can reduce the activity of enzymes and so reduce growth rates.
- the absence of unwanted microorganisms
- refers to the measures to ensure that unwanted microorganisms do not contaminate the culture that is being grown or the products that are extracted
Aseptic technique in Laboratory/ Starter Culture Level
- All apparatus is sterilized before and after use, e.g. by heating in a flame until glowing, by UV light or steaming at 121oC for 15 minutes in an autoclave (large pressure cooker).
- Carried out in a fume cupboard or a laminar flow cabinet where air circulation carries any airborne contaminants away.
- Cultures of microorganisms are kept closed where possible and away from the bench space when open and in use.
Aseptic technique at Large-scale Culture Level
- Washing, disinfecting and steam cleaning the fermenter and associated pipes removes excess nutrient medium and kills microorganisms.
- Surfaces made of polished stainless steel prevent microorganisms and medium sticking to surfaces.
- Sterilising all nutrient media before adding to the fermenter prevents introduction of contaminants.
- Fine filters on inlet and outlet pipes avoid microorganisms entering and leaving the fermentation vessel.
The nutrient medium in which the microorganisms grow could also support the growth of many unwanted microorganisms. Any unwanted microorganism is called a contaminant. Unwanted microorganisms:
- Compete with the culture microorganisms for nutrients and space.
- Reduce the yield of useful products from the culture microorganisms.
- May cause spoilage of the product.
- May produce toxic chemicals.
- May destroy the culture microorganism and their products.
This is the end of the topic
Drafted by Eva(Biology)