Microorganisms and Biotechnology
The earliest recorded use of microorganisms by people was around 6000 BC when the Sumerians and Babylonians were using yeast to make beer.
By 4000 BC the Egyptians were using yeast to make their bread rise.
These are all examples of the development and use of biotechnology over several millennia.
Defining biotechnology
Biotechnology involves applying biological organisms or enzymes to the synthesis, breakdown, or transformation of materials in the service of people.
It describes a range of processes, from the traditional production of cheese, yoghurt, wine, bread, and beer to the latest molecular technologies using DNA manipulation to produce genetically engineered microorganisms synthesising drugs such as insulin and antibiotics, and the use of biological systems to remove soil and water pollution in processes known as bioremediation.
The most commonly used organisms in biotechnology processes (bioprocesses) are fungi, particularly the yeasts, and bacteria, which are particularly useful in the newer technologies based around genetic manipulation.
The use of microorganisms
Most biotechnology involves using biological catalysts (enzymes) in a manufacturing process and the most stable, convenient, and effective form of the enzymes is often a whole microorganism.
Microorganisms are ideal for a variety of reasons.
- There are no welfare issues to consider – all that is needed is the optimum conditions for growth.
- There is an enormous range of microorganisms capable of carrying out many different chemical syntheses or degradations that can be used.
- Genetic engineering allows us to artificially manipulate microorganisms to carry out synthesis reactions that they would not do naturally, for example, to produce human insulin.
- Microorganisms have a very short life cycle and rapid growth rate. As a result, given the right conditions of food, oxygen, and temperature, huge quantities of microorganisms can be produced in short periods of time.
- The nutrient requirements of microorganisms are often very simple and relatively cheap. Genetic manipulation means we can modify them so that the microorganisms can utilise materials which would otherwise be wasted, making the raw materials for microorganism-controlled syntheses much cheaper than the raw materials needed for most other industrial processes.
- The conditions in which most microorganisms need to grow include a relatively low temperature, a supply of oxygen and food, and the removal of waste gases.
- They provide their own catalysts in the form of enzymes. This makes bioprocesses relatively cheap compared to the high temperatures and pressures and expensive catalysts often needed in non-biological industrial processes.
Indirect food production
Microorganisms are widely used in biotechnological processes to make food such as bread, yoghurt, and cheese.
The microorganisms have an indirect effect.
It is their actions on other foods that are important.
When you eat bread, you are mainly eating flour, when you eat yoghurt or cheese it is mainly milk.
The advantages of using microorganisms in this way are all of the ones listed previously as advantages of using microorganisms in biotechnology generally.
There are a few disadvantages to using microorganisms indirectly in the production of human foods.
If the conditions are not ideal (e.g., too hot or too cold) the microorganisms do not grow properly and so they do not work efficiently.
Conditions that are ideal for the microorganisms can also be ideal for microorganisms that cause the food to go off or cause disease and so the processes have to be sterile.
Increasingly the microorganisms used in food production have been genetically engineered, and some people have ethical issues with the use of GM organisms, although this is generally much less the case with microorganisms than with animals and plants.
There are around 900 different types of cheese made around the world.
Some are still made by very small-scale, traditional methods and others are produced commercially on a very large scale.
Direct food production
People have eaten fungi for thousands of years in the form of a wide variety of mushrooms.
In recent times, facing potential protein shortages around the world, scientists are developing more ways of using microorganisms to directly produce protein you can eat.
It is known as single-cell protein or SCP.
The best-known SCP is Quorn.
This is made of the fungus Fusarium venetatum, a single-celled fungus that is grown in large fermenters using glucose syrup as a food source.
The microorganisms are combined with albumen (egg white) and then compressed and formed into meal substitutes.
Quorn is not only suitable for vegetarians, but it is also a healthy choice as it is high in protein and low in fat.
People are very conservative in their food choices and when the new food was launched, no mention was made of the fungi used to produce it.
Using the term mycoprotein meant most people did not recognise what it was made of.
However, a combination of good marketing and a good product meant that people tried Quorn and liked it, and it has been internationally successful as a novel protein food.
Other attempts to make proteins from microorganisms have not yet been as successful.
Yeasts, algae, and bacteria can be used to grow proteins that match animal proteins found in meals as well as plant proteins.
They can be grown on almost anything, are relatively cheap and low in fat, yet none of the alternative protein sources has proved successful so far.
People have many reservations about eating food grown on waste.
Increasingly single-celled proteins are being used to feed animals that we prefer to eat from fish to cattle.
If the world protein shortage continues, however, people may yet turn to eating foods made directly from microorganisms.
Examples of microorganisms involved in commercial processes.
Brewing
Yeast – respires anaerobically to produce ethanol. Traditional yeasts ferment at 20-28 °C. GM yeasts ferment at lower, and therefore cheaper, temperatures, clump together (flocculate) and sink at the end of the process leaving the beer very clear.
Process
- Malting: Barley germinates producing enzymes that break starch molecules down to sugars which yeast can use. Seeds are then killed by slow heating but enzyme activity is retained to produce malt.
- Mashing: The malt is mixed with hot water (55-65°C) and enzymes break down starches to produce wort. Hops are added for flavour and antiseptic qualities. The wort is sterilised and cooled.
- Fermentation: Wort is inoculated with yeast. Temperature maintained for optimum anaerobic respiration (fermentation). Eventually, yeast is inhibited by falling pH, build-up of ethanol, and lack of oxygen.
- Maturation: The beer is conditioned for 4-29 days at temperatures of 2-6 °C in tanks
- Finishing: The beer is filtered, pasteurised, and then bottled or canned with the addition of carbon dioxide
- The alcohol content varies between about 4% and 9%.
Yoghurt making
Bacteria – often Lactobacillus bulgaricus (forms ethanal) and Streptococcus thermophilus (forms lactic acid). Both produce extracellular polymers that give yoghurt its smooth, thick texture.
Process;
- Skimmed milk powder is added to milk and the mixture is pasteurised, homogenised, and cooled to about 42 °C.
- The milk is mixed with a 1:1 ratio of Lactobacillus bulgaricus and Streptococcus thermophilus and incubated at around 45 °C for 4-5 hours.
- At the end of the fermentation, the yoghurt may be put into cartons at a temperature of around 10 °C as plain yoghurt or mixed with previously sterilised fruit.
- Thick-set yoghurts are mixed and fermented in the pot.
- Yoghurt has a shelf-life of about 19 days if stored at 2-3 °C.
Baking
Yeast – mixed with sugar and water to respire aerobically. Carbon dioxide produced makes bread rise.
Process;
- The active yeast mixture is added to flour and other ingredients. Mixed and left in a warm environment to rise.
- Dough is knocked back (excess air removed), kneaded, shaped, and left to rise again.
- Cooked in a hot oven – the carbon dioxide bubbles expand, so the bread rises more. Yeast cells are killed during cooking.
Cheese making
Bacteria – feed on lactose in milk, changing the texture and taste, and inhibiting the growth of bacteria which make milk go off.
Process;
- The milk is pasteurised (heated to 95 °C for 20 seconds to kill off most natural bacteria) and homogenised (the fat droplets are evenly distributed through the milk).
- It is mixed with bacterial cultures and sometimes chymosin enzyme and kept until the milk separates into solid curds and liquid whey.
- For cottage cheese, the curds are separated from the whey, packaged, and sold.
- For most cheese, the curds are cut and cooked in the whey then strained through draining moulds or cheesecloth. The whey is used for animal feeds.
- The curds are put into steel or wooden drums and may be pressed. They are left to dry, mature, and ripen before eating as the bacteria continue to act for anything from a few weeks to several years.
Advantages of using microorganisms to produce human food
- Microorganisms can use a wide variety of waste materials including human and animal waste, reducing costs
- They reproduce fast and produce protein faster than animals and plants
- Also, microorganisms have a high protein content with little fat.
- Microorganisms can be genetically modified to produce the protein required
- No welfare issues when growing microorganisms
- Production of microorganisms is not dependent on weather, breeding cycles etc. It takes place constantly and can be increased or decreased to match demand.
- They can be made to taste like anything
Disadvantages of using microorganisms to produce human food.
- Need sterile conditions that are carefully controlled adding to costs
- Often involve genetically modified (GM) organisms and many people have concerns about eating GM food
- The protein has to be purified to ensure it contains no toxin or contaminants
- Also, the microorganisms have to be separated from the nutrient broth and processed to make the food.
- Many people dislike the idea of eating microorganisms grown on waste
- Moreover, some microorganisms can also produce toxins if the conditions are not maintained at the optimum.
- Microorganisms have little natural flavour hence the need for additives
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