Microbiology

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Growing Microbes

Microbes are grown on agar. Agar contains carbohydrate as an energy source, but may also have some minerals, proteins and vitamins as extra nutrients.

In schools, these cultures should be incubated at 25C. If any higher temperatures are used, pathogens may be produced.

Inoculating loops are used to transfer the microbes to the agar, and must be sterilised.

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Food production using yeast

Yeast cells respire aerobically and quickly when oxygen is present, thus, they reproduce rapidly.

Without oxygen, they repire anaerobically and produce alcohol; this is fermentation.

When beer is brewed, the starch in the barley grains, is used as the carbohydrate energy source for the yeast. 

The starch is first broken down into sugars by enzymes  during the germinating process, once this is complete, hops are added for flavour.

With wine, the grapes contain natural sugars and are thus an energy source.

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Food production using bacteria

Bacteria is used in the making of cheese and yoghurt.

There are three stages in making yoghurt;

Bacteria are added to warm milk

The milk sugar (Lactose) is fermented by bacteria, producing lactic acid.

The lactic acid causes the milk to clot, forming yoghurt.

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Antibiotic Production

Penicillum is made from the mould Penicillium in a fermenter.

The solution inside the vessell contains sugar for energy and some other nutrients including nitrogen.

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Large scale microbe production

Industrial fermenters are used to grow microorganisms, conditions are very carefully monitered;

Air supply providing oxygen for respiration

Stirrer, to spread out microoragnisms and make sure the temparature is the same all around

Water cooled jacket round the outside, and the microorganisms respire and release heat, and a constant temp must be maintained.

Sensors for PH and Temperature.

Fusarium, grown for veggies in meat products, is grown to produce mycoprotein, and grown aerobically on starch, and the mycoprotein harvested.

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Biogas

Plants and waste material can be broken down anaerobically to make biogas, mostly methane.

Done on a large scale with sewage works and sugar factory waste.

The energy source is mainly carbohydrate.

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More Biofuels

Sugar cane juices, derived from maize starch by the action of the carbohydrase enzyme, can be fermented to produce ethanol. 

Microorganimsms respire anaerobically in this process.

Ethanol must be distilled.

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