Study of microorganisms. Microorganisms can be grown in an agar culture medium with a carbohydrate energy source and various mineral, vitamins and proteins. Maximum incubation temperature in schools in 25c, because this reduces the likelihood of harmful pathogens growing.
Yeats respire aerobically to provide energy for the cells producing waste water and carbon dioxide. Fermentation is the anaerobic respiration of yeast, producing ethanol and carbon dioxide. To make bread, mix yeast with sugar (energy source for respiration) and then mix this with water and flour- the yeast grows and respires, producing carbon dioxide which makes the bread rise.
Beer making is made my malting- soak barley grains in water and keep them warm, and as germination begins, enzymes break down the starch into a sugary solution, which is used as an energy source for the yeast. Yeast + sugar solution = fermentation to produce alcohol. Wine making uses the natural sugar found in fruits (e.g. grapes) as energy source. Yeast + water + juice (sugary solution) = fermentation. Yeats is then filtered out of wine, and wine is stored to mature.
To make yoghurt: add a starter culture of the right type of bacteria to warm milk, keep mixture warm so bacteria grow, reproduce and ferment, bacteria break down lactose in the milk to produce lactic acid- this is called lactic fermentation, lactic acid causes milk to clot and solidify into yoghurt, yoghurt-forming bacteria help to prevent the growth of bacteria which make milk go off. To make cheese: add a starter culture of bacteria to warm milk (the type of bacteria added is different from the type used to make yoghurt), the bacteria break down lactose into lactic acid, but this time much more lactic acid is produced, so the curds are much more solid than the yoghurt ones, enzymes are added to increase separation of milk, when milk has curdled, you can separate the curds form liquid whey (curds are used for cheese-making), You cut and mix curds with salt and other bacteria/moulds and leave them to dry.
As the number of microorganisms in fermenters increases: the food is used up, the temperature rises because of the metabolism of millions of microorganisms, oxygen levels fall as it is used up in respiration, pH changes due to a build up of carbon dioxide, other waste products may build up and poison the culture.
Fermenters are the large vessels used to carry out industrial fermentation. They have: an oxygen supply to provide oxygen for respiration, stirrer to maintain an even temperature and that oxygen and food are evenly spread, water-cooled jacket which removes excess heat produced in respiration and measuring instruments to monitor pH and temperature.
Mycoprotein is a food based on fungi (produced using Fusarium). This grows and reproduces on a cheap sugar supply, and needs aerobic conditions. It is versatile, high in protein and fibre and low in fat and calories.
Alexander Fleming extracted penicillin from a mould called Penicillium Notatum. Howard Florey and Ernst Chain were able to extract penicillin for mass production.
The Penicillium mould is grown in a sterilised medium with sugar, amino acids, mineral salts. The broth is stirred by large fermenters, sterile air is blown in to provide oxygen and temperature is controlled by a cooling jacket. During the first 40 hours, mould grows rapidly and uses up nutrients. After nutrients have gone, mould begins to produce penicillin, so there is a 40 hour lag period between start of fermentation, and production of penicillin.
Biogas is a flammable mixture of gases formed when bacteria break down plant material and animal waste products (it is mainly methane) in anaerobic conditions. Bacteria in biogas generators work best at 30c. The process generates heat (exothermic), so if heat energy is put in at the start and the generator is well insulated, they can be used anywhere.
Batch generators make biogas in small quantities and manually loaded with waste. Continuous generators make biogas all the time- biogas is produced at a steady rate (large-scale). When designing a generator, you need to think about the: Cost- continuous generators are more expensive, convenience- batch generators are less convenient, efficiency- need to be well insulated and no leaks and position- away form homes.
Many different organisms are involved in the breakdown of material in biogas production. Sugar cane contains sucrose (high in carbohydrates) and maize contains starch which can be broken down using carbohydrase. Yeast + sugary products from cane and maize = ethanol and water (anaerobic respiration).
Ethanol can then be extracted by distillation. Advantages of ethanol as a fuel: does not produce toxic gases when you burn it, ethanol + Petrol = Gasohol, ethanol is carbon neutral (no overall increase in carbon dioxide in the atmosphere when you burn it). Disadvantages of ethanol as a fuel: Takes a lot of plant material to produce ethanol.