Microorganisms are grown on Perti dishes in agar (culture medium).
- carbohydrate (energy source)
- supplementry nutrients (proteins, vitatmins, minerals)
Instruments used like culture medium, Petri dish and inoculating loop need to be sterilised.
In schools, culture is incubated at 25 degrees C as higher temperatures can cause harmful pathogens to grow.
Food production using yeast.
Yeast is a single-celled organism with a nucleus, cytoplasm, cell membrane and a cell wall.
When O2 is present they respire aerobically and reproduce quickly.
However, when O2 is not present they respire anaerobically and produce ethanol and CO2 . This is called fermentation.
Making beer from yeast:
- starch in barley grains is used as the carbohydrate energy source
- starch is broken down into sugars in the barley grains by enzymes during the germinating process
- when there sugars have been fermented hops are added to give flavour
- beer is pasturised before sold to kill microbes
Making wine from yeast:
- fruit is crushed this gets juice and sugars out of it
- not always necessary to add yeast (there's natural yeast in fruit), yeast is needed as an energy source
- after fermentation the wine is cleared, stabilised and matured
Food production using bacteria.
Bacteria are used in the manufacture of cheese and yogurt.
- bacteria are added to warmed milk
- milk sugar (lactose) is fermented by the bacteria, producing lactic acid
- lactic acid causes milk to solidify and yogurt is formed
- milk protein turns solids to curds
- milk protein is preserved as cheese
- curds get more acidic which encourages solidification
- curds are separated from the liquid by filtration
- curd is made into hard cheese by filtering it, flavouring it and pressing it.
Large-scale microbe production.
Microorganisms cna be grown on a large scale in an industrial ferementer.
Fermenters are carfully monitored:
- O2 is provided for respiration
- a stirrer is used to keep microorganisms spead out and ensure a constant temperature throughout the vessel
- a water-cooled jacket also helps maintain a constant temperature are microorganisms release heat
- sensors to monitor pH and temperature
A mycoprotein can be produced using the fungus, Fusarium (which is grown aerobically on starch)
Mycoprotein is a protein-rich food for veggies.
Antibiotics are produced in fermenters.
Penicillin is made from the mould Penicillium but only when most of the nutrients are used up.
The culture medium contains:
- sugar (for energy)
- other nutrients, including nitrogen
Biogas (fuel for energy) is mainly methane from plants and waste products (CO2) which are broken down anaerobiocally.
It can be made on a large scale with wast from sugar factories or sewage works.
It can be used on a small scale at home or on a farm.
Sugar cane juices and glucose (derived form maize starch by the action of a carbohydrase enzyme) can be fermented to produce ethanol.
The ethanol produced (from the anaerobic respiration of microorganisms) can be distilled and used as a fuel.
Using ethanol could replace fossil fuels in the future.
Ethanol is more 'carbon friendly' so better for the environment.