Biology Use of Biological Resources

How is milk fermented to produce yoghurt? (5 steps)

1. Equipment is sterilized to kill microbes.

2. Milk is pasteurized (heated) to kill harmful microbes, then cooled.

3. Lactobacillus bacteria are added into a vessel called a fermenter.

4. Bacteria ferment lactose sugar into lactic acid.

5. Lactic acid causes milk to solidify and produce yogurt.

Why are nutrients required in a fermenter?

Needed by microorganisms for growth

Why must pH be controlled in a fermenter?

For the microorganisms’ enzymes to work efficiently and keep the rate of reaction and product yield as high as possible

Why must temperature be controlled in an optimum level?

A water-cooled jacket akes sure temperature is kept at an optimum level so that overheating does not occur and denature the enzymes.

Why are fermenters stirred?

To distribute heat evenly AND increase product yield because microorganisms can always access nutrients needed for growth.

Why is oxygen needed in fermenters?

Oxygen is added by pumping in sterile air to increase product yield because microorganisms can always respire to provide the energy for growth.

Why are aseptic conditions required in fermenters?

Superheated steam kills unwanted microbes, ensuring microorganisms aren’t competing with other unwanted microorganisms or get contaminated.

How is yeast used to make bread?

Yeast acts on sugar to form carbondioxide in aerobic respiration, which causes the dough to rise. When the bread is baked high temperatures kill the yeast and alcohol is boiled away.

Restriction enzymes

Used in genetic engineering to cut out a section from a molecule of DNA

Ligase enzymes

Join two pieces of DNA together

Recombiant DNA

DNA made by genetic engineering, combining DNA from two species of organisms

Types of vectors

Plasmids, viruses

Genetic engineering steps (6 steps)

1. DNA that must be inserted is cut out with restriction enzyme. The vector DNA is cut open with the same restriction enzyme.

2. The vector DNA and DNA that is to be inserted is glued together by ligaze enzymes to form a recombiant DNA.

3. The recombiant DNA is inserted into other cells such as bacteria.

4. Bacteria are grown in culture.

5. As bacteria multiply, the vector multiplies.

6. Bacteria produce the desired protein from the recombiant DNA.