11

23 Biotechnology

Summary

7 In industry, enzymes are often immobilised, for example within alginate beads. Th is prevents the enzyme from mixing with the product, making it easy to re-use the enzymes and avoiding the need to remove them from the product before further processing or sale.

8 Immobilised glucose oxidase is used on dip sticks to detect the presence of glucose in blood or urine. Th e enzyme changes glucose to gluconolactone and hydrogen peroxide, which causes a colour change in another chemical on the stick. Biosensors use the same principle but produce a small electric current instead of a colour change, which provides a direct digital readout.

9 Monoclonal antibodies are antibodies that are all identical to each other. Th ey are produced by fusing a plasma cell with a cancer cell to produce a hybridoma, which divides repeatedly to form many genetically identical cells that all produce the same antibody. Monoclonal antibodies are used in diagnosis, for example of pregnancy, and in the treatment of disease such as cancer.

1 Bacteria can be used to extract metals from low-grade sulfi de ores by changing them to soluble sulfates, which can be washed out using water. Th is is called bioleaching.

2 Penicillin is made by culturing the fungus Penicillium in a fermenter. Th is uses batch culture, because penicillin is a secondary metabolite and is produced only when the funguss growth phase has slowed down. Many kinds of enzymes are also manufactured using batch culture of fungi or bacteria.

3 Mycoprotein is made by culturing the fungus Fusarium in a fermenter. Th is uses continuous culture, in which nutrients are steadily added to the fermenter, and the fungal hyphae are steadily removed.

4 Batch culture has several advantages over continuous culture, but the method chosen is determined by the conditions required by the microorganism to manufacture the required product.

5 Th e antibiotic penicillin prevents the production of new cell walls in bacteria and so does not aff ect viruses or human cells, neither of which have cell walls.

6 Resistance to antibiotics can arise because some bacteria may, by chance, contain a resistance gene. Th e bacteria survive when exposed to the antibiotic and can then reproduce to form a large population of bacteria all containing this gene.

Cambridge University Press 2013 Summary: Chapter 23

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