Biology GCSE - B3 Biotechnology - Edexcel

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Biotechnology Objectives


Recall that prebiotics are functional foods which are marketed as providing health benefits.

Prebiotics and probiotics are both sources of bacteria, in this case it is the good bacteria, and they stimulate the growth of useful bacteria in the colon. They are non-digestible functional foods. They are marketed as providing health benefits because prebiotics stimulate ‘beneficial bacteria’ (Lactobacillus and Bifidobacterium), these are naturally found in the human gut, the growth and development of beneficial bacteria results in health benefits.


Recall that prebiotics contain oligosaccharides.

Oligosaccharides are an added sugar that is added to prebiotics; these feed the good bacteria and make them multiply.


Describe the production of yoghurt from milk as the conversion of lactose into lactic acid using bacteria.

Yoghurt production:

1.      Milk is used to sterilise it, killing any bacteria already present.

2.      Then the milk is stirred thoroughly to mix up its ingredients and milk protein is added.

3.       A starter culture of lactobacillus bacteria is added to the milk.

4.      The lactobacillus bacteria ferment the sugar lactose in the milk into lactic acid while it’s warm.

5.      The lactic acid lowers the pH of the milk (the milk becomes acidic) to the point where the milk proteins coagulate.

6.      The semi – solid milk is raw yoghurt.

7.      The raw yoghurt is cooled quickly.

8.       Different flavourings of fruit added to yoghurt. The pots are then sealed.

The yoghurt has been changed from lactose into lactic acid using lactobacillus bacterium.


Explain that the commercial production of soy sauce includes fermentation of a mixture of cooked soya beans and roasted wheat using aspergillus, further fermentation using yeasts and then lactobacillus filtration, pasteurisation and sterile bottling.

Soy sauce production:

1.      Soya beans are cooked, which kills all of the bacteria on their surface, and mixed with ground roasted wheat.

2.      Asperguillus mould is added to the mixture.

3.      The mixture is spread out on warm shallow trays and supplied with air.

4.      Enzymes produced by the asperguillus mould catalyse the breakdown of proteins and carbohydrates in the mixture.

5.      The amino acids and sugar content of the mixture increases.

6.      Brine (sodium chloride solution) is added to the mixture. It gives soy sauce its salty taste and helps to preserve the final product.

7.      Yeasts and lactobacillus bacteria, which are able to tolerate high levels of sodium chloride and low levels of oxygen, are added to the brine mixture. The conditions stop the activities of the asperguillus mould.

8.      The sugars in the mixture are fermented by the yeasts and lactobacillus bacteria

9.      Raw soy sauce is drained from the mixture.

10.  The liquid is filtered and cleared of any sediment (filtration).

11.   The filtered and cleared liquid is heated to 72oC (pasteurisation) and stored to allow its flavours to develop.

12.   It is then placed in




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Naomi Arnold


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Thanks! It's so detailed !

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