- Is the industrial use of living organisms (bacteria and fungi) to produce food, drugs and other commercial products.
- e.g. cheese, yoghurt, beer and vinegar are foods produced by microbes.
- Drugs synthesised by microbes include insulin and antibiotics e.g. penicillin.
- Microbes are also used to synthesise biofuels and the enzymes added to biological washing powders.
Why are microbes used?
- Fast growth rates.
- They produce proteins or chemicals that are secreted into the surrounding medium.
- Can be genetically engineered to produce specific products e.g bacteria with the human gene coding for insulin - for diabetics.
- They grow well at low temperatures.
- Can be grown anywhere in the world, don't depend on climate.
- They generate purer product than use of chemical processes as there are fewer side reactions.
- Can be grown using nutrient materials which would otherwise be useless or even toxic.
Growth of microbes in a closed culture
- Bacteria divide by binary fission; a cell divides into 2 daughter cells as often as once every 20 minutes.
- The number of cells descended from one original is 2^n (2 to the power n) where n is the number of divisions.
- The time taken for the population to double is called the generation time.
- LAG PHASE - Bacteria adjust to conditions and growth medium. Proteins, ribosomes and enzymes are synthesised. Water is absorbed and the cells expand. Genes are switched on to make new enzymes. Population rate is slow as the cells are not dividing.
- LOG/EXPONENTIAL PHASE - There are no limiting factors to population growth and the cells divide exponentially (population doubles every generation). Substances produce by microbes in this phase are primary metabolites.
- STATIONARY PHASE - Reproduction rate = death rate. Population remains constant. Oxygen, respiratory substances and vitamins have become limiting, and toxic waste products e.g. carbon dioxide are building up. Some substances are only produced in this phase - secondary metabolites, e.g. the Penicillum fungus only produces penicillin in the stationary phase.
- DEATH PHASE - Population starts to decline, because death rate>reproduction rate. Toxic metabolic waste kills cells, and nutrients are used up. Eventually all cells die.
How biotechnological cultures are carried out
1. Bacteria and fungi are screened to find out if they produce useful metabolic products.
2. The microbe is grown in…