Biotechnology is the industrial use of living organisms (or parts of living organisms) to produce food, drugs or other products.
Microorganisms are often used in biotechnological processes because they grow rapidly in favourable conditions, with a generation time of as little as 30 minutes. Often produce proteins or chemicals that are given out into the surrounding medium and can be harvested. Can be genetically engineered to produce specific products. Grow well at relatively low temperatures, much lower than those required in the chemical engineering of similar processes. Can be grown anywhere in the world and are not dependent on climate. Tend to generate products what are in a more pure form than those generated via chemical processes. Can often be grown using nutrient materials that would otherwise be useless or even toxic to humans.
Standard growth curve of a microorganism in a closed culture.
Lag phase: Organisms are adjusting to the surrounding conditions. This may mean taking in water, cell expansion, activating specific genes and synthesising specific enzymes. The cells are active but not reproducing so population remains fairly constant. The length of this period depends on the growing conditions.
Log phase: The population size doubles each generation as each individual has enough space and nutrients to reproduce. In some bacteria the population can double every 20-30 minutes. The length of this pahse depends on how quickly the organisms reproduce and take up the available space and nutrients.
Stationary phase: Nutrient levels decrease and waste products like carbon dioxide and other metabolites build up. Individual organisms die at the same rate at which new individuals are being produced. In an open system this would be the carrying capacity.
Death phase: Nutrient exhaustion and increased levels of toxic waste products and metabolists leads to the death rate increasing above the reproduction rate. Eventually all the organisms will die in a closed system.
Adsorption: Enzyme molecules are mixed with the immobilising support and bind to it due to a combination of hydrophobic interactions and ionic links.