In this chapter of I/GCSE Biology, we will discuss about microbiology.
Growing Microbes
To find out about microbes you need to culture them (grow in a colony to study lots of them).
Microorganisms need a culture medium containing carbohydrate to act as an energy source. Along with this, mineral ions, and sometimes extra proteins and vitamins are included. You also need warmth and moisture.
The medium is sometimes an Agar substance, which forms a jelly in hot water.
The medium is also sometimes a broth in a Culture flask.
Safety Precautions
There is always a risk of mutation when growing microbes, which could result in dangerous pathogens.
The original, safe microbes could also be contaminated by disease causing pathogens.
In the lab, you have to avoid contamination of dangerous microorganisms
Food Production Using Yeast
Refer to I/GCSE Biology, yeast is a single celled organism, each of which have a Nucleus, Cytoplasm and a Membrane surrounded by a cell wall. The way in which they reproduce is by asexual Mitosis. When yeast cells have plenty of Oxygen they respire Aerobically. When the yeast cells break sugar down Anaerobically, they produce Ethanol and Carbon Dioxide. This process is called Fermentation. The Carbon Dioxide makes dough rise when making bread.
Making Alcoholic Drinks
In making both Beer and Wine, Yeats is added to sugar, which is left to ferment. The yeast will respire Anaerobically, creating ethanol (Alcohol). Alcohol is also poisonous to the yeast itself, which is why the alcohol content in wine Is rarely more than 14%.
Food Production using Bacteria
Making Yoghurt
Traditionally, yoghurt is fermented whole milk but now we can make it from semi-skimmed, skimmed and even soya milk. Yoghurt is formed by the action of bacteria on the Lactose (Milk Sugar) in the milk. A starter culture is added to warm milk, and then the culture reproduce, grow, and ferment. As the bacteria break down the Lactose In the milk, they produce Lactic Acid which gives yoghurt its sharp tangy taste. This is known as Lactic Fermentation. It also clots the milk to a smooth, thick texture.
Cheese Making
Like yoghurt making, cheese making depends on the reaction of bacteria with the milk. Like yoghurt making, you add a starter culture of bacteria to warm milk. The difference is the type of bacteria. The bacteria in cheese making also converts Lactose to Lactic Acid, but makes much more of the acid. As a result the solid curds are much more solid. Enzymes are also added to increase the separation of the milk. When it has curdled you can see the separate Curds and Whey. The curds are used for cheese making. Then other bacterium can be added to alter the flavour of the cheese.
Large Scale Microbe Production
If we want to collect and use the products made by microbes, we need to grow the microorganisms on a large scale for a long time.
Fermenters
In I/GCSE Biology, the ideal conditions the numbers of bacteria can double every 20 minutes, but these conditions are rare. What actually happens is shown in the picture below.
As the number of bacteria rise, the conditions change. (Food used up, temperature rises, Oxygen levels fall)
The Carbon Dioxide waste also changes the pH value, which can affect enzyme action in the culture.
Fermenters are designed to overcome these problems. They react to changes, keeping conditions stable to ensure we can harvest the maximum yield. Industrial Fermenters usually have:
- An Oxygen supply to provide O2 for Respiration
- A stirrer to maintain temperature and evenly spread Oxygen and food throughout
- A water cooled jacket which removes excess heat produced by respiration
- Measuring instruments to monitor factors such as pH and Temperature so that changes can be made
Mycoprotein Production
When it comes to I/GCSE Biology, Mycoprotein is a protein made from fungus, and is made by the fungus Fusarium. This grows and reproduces rapidly on a cheap sugar syrup in large Fermenters. It needs Conditions to grow successfully.
The Mycoprotein can be given a range of tastes and flavours to make it similar to many other foods, such as meat and fish. It is a high protein, low fat meat substitute.
And we're done with this topic! Well Done!
