6.4.6 other processes involving biotechnology

large stainless steel containers = fermenters

• temperature = too hot & enzymes denature or too cold & growth will be limited • nutrients available = microorganisms need nutrients to grow & synthesise the product –> sources of carbon, nitrogen, minerals & vitamins are needed • oxygen availability = most organisms respire aerobically • pH = enzyme activity, hence growth & synthesis are affected by extremes • concentration of product = if product allowed to build up, it may affect synthesis process

• sterilised using superheated steam • then, filled with components required for growth & supplied with starter culture of microorganisms • culture left to grow & synthesise products

• pressure vent = prevents gas build-up • air inlet = sterile air provides oxygen in aerobic fermenters • mixing blades • water jacket inlet = allows circulation of water around fermenter to regulate temperature • outlet tap for draining fermenter • motor = rotates blades to mix culture evenly • inlet for addition of nutrients • water jacket outlet • electronic probes = measure oxygen, pH & temperature levels • air outlets (often in a ring) = air bubbles out from outlets, mixing with culture (sparging)

filters = prevent contamination

products which are synthesised by the microorganism during normal metabolism when they are actively growing

• primary metabolites are continually released from cells & can be extracted continuously from fermenting broth • broth topped up with nutrients as these are used by the microorganisms • some of broth removed regularly to extract the product & remove cells from the broth (otherwise population becomes too dense) • keeps microorganisms growing at specific growth rate

products which are produced only when cells are placed under stress eg. high population density or limited nutrient availability –> produced mostly during stationary phase of growth

• culture set up with limited quantity of nutrients & allowed to ferment for specific time • after this time, the fermenter is emptied & product can be extracted from culture

• compete with cultured microorganisms for nutrients & space • reduce yield of useful products • spoil the product

• produce toxic chemicals • destroy cultured microorganisms & their products