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Household Microbes

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You’ve learned all about how microbes live all over the world, all around us. But did you know that you can also find them in your own home? Humans have harnessed microbes to do all sorts of useful jobs for them.

Challenge: Scavenger Hunt

Here’s a scavenger hunt for you to do – if you can’t find something in your house why not draw a picture?

  • Yeast or bread
  • Cheese or yogurt
  • Biological washing powder
  • Vinegar
  • Chocolate
  • Quorn

Want to learn more? Here’s some facts about the microbes behind these useful and sometimes tasty products!

Bread

Bread

Bread is made using baker’s yeast, which you might remember is a type of fungus, a eukaryotic microbe. The proteins (called enzymes) made by the yeast break down the large flour molecules into sugars. The sugar is converted to carbon dioxide and alcohol and the carbon dioxide is trapped within the dough causing it to rise and take on a bubbly structure.
Yogurt

Yogurt

Yogurt is a fermented milk product. The sugar in the milk (lactose) is converted to lactic acid by lactic acid bacteria which makes the milk thicken. Flavours can then be added. Lactococcus lactis and Bifidobacterium are common bacteria used in this process.
Cheese

Cheese

Like yogurt and sour cream, cheese is made from milk that contains the sugar lactose and a protein called casein. During cheese production the lactose is converted to lactic acid and the protein is thickened. Water is removed, leaving a semi-solid product. This relies on fermentation using lactic acid bacteria. Cheese also needs ripening to give it flavour. This also uses bacteria and depending on the exact mix of the microbes used the flavour can be very different.
Washing Powder

Washing Powder

Biological washing powders contain enzymes that are made by bacteria. Bacteria do not have a “stomach” but instead make enzymes that they put into the environment around them. Here they break down the food into smaller parts that can be taken up and used. We have adopted this for washing powders where the enzymes help to break down the food on our dirty clothes.
Vinegar

Vinegar

Vinegar is a solution that is mainly acetic acid. This is produced by fermentation of ethanol by acetic acid bacteria. This is also what happens to make cider, wine etc.
Chocolate

Chocolate

Cocoa beans are seeds that form inside pods. They are coated in a sugary material that needs breaking down. Microbes help with this. The beans are “fermented” and this makes the bean taste chocolatey. (A similar process is used for making coffee beans).
Quorn

Quorn

Quorn is a meat substitute that is made from a fungus called Fusarium venenatum. The fungus grows in large tanks and then is collected and dried.

Here’s a video from TED-Ed that will tell you all about these tasty treats and more.

Yeast

In the picture, you can see the most common bread yeast, Saccharomyces cerevisiae, as viewed under a microscope. This image was taken by scientist Viola Denninger (Tanaka Lab, University of Dundee) who uses yeast in her experiments.

We will investigate yeast a little bit more. Yeast is a microbe that is contained in dough and is needed to make bread rise. Yeast turns sugars in the dough into alcohol and a gas called carbon dioxide in a process called fermentation. As the dough heats up the bubbles of gas get bigger and the bread rises.

Activity: Today you will test the best way to make yeast grow with our experiment Yeast Races! The goal is to compare which food is best suited for yeast to make the bread rise.
Yeast
Yeast
Yeast Races Worksheet
Yeast Races (PDF)

If you have enjoyed these activities please share them with your friends and family.