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Cambridge IGCSE Biology · 0610

Chapter 21: Biotechnology and genetic modification (Part 1)

Introduction to biotechnology

Definition
Biotechnology involves using microorganisms and biological substances to carry out functions in manufacturing processes.
Use of bacteria
Bacteria are particularly useful in biotechnology and genetic modification because of their rapid reproduction rate and their ability to synthesise complex molecules.
Advantages
There are no ethical concerns regarding the manipulation of bacterial DNA, and they contain plasmids (circular rings of DNA) which are easily modified.

Exam Traps

  • Do not say all biotechnology uses animals — bacteria and fungi are common industrial organisms.
  • Avoid confusing plasmids (bacterial) with chromosomes in the nucleus.

Applications of biotechnology

Yeast in bread-making
Yeast respires anaerobically, releasing carbon dioxide bubbles that make dough rise.
Yeast in biofuels
The ethanol released during anaerobic respiration in yeast is used as a sustainable alternative to fossil fuels.
Pectinase in fruit juice
Pectinase is an enzyme used to break down pectin in plant cell walls. This releases the cell contents, significantly increasing the yield of fruit juice and making it clearer.
Biological washing powders
These contain enzymes to break down stains into water-soluble products:
  • Amylases break down starch.
  • Lipases break down fats and oils.
  • Proteases break down proteins.
These work best at lower temperatures to avoid denaturation.
Lactase
Used to produce lactose-free milk by breaking down lactose into glucose and galactose, which can be safely digested by lactose-intolerant individuals.

Exam Traps

  • Do not say yeast makes bread rise by producing ethanol — CO2 bubbles cause the rise.
  • Do not claim biological washing powders work best at high temperatures — lower temperatures avoid enzyme denaturation.

Industrial fermenters

Fermenters are used for the large-scale production of products like penicillin (from fungi), insulin (from bacteria), and mycoprotein (from fungi).

Temperature
Maintained (usually 25–30°C) for optimum growth; prevents killing the microorganisms.
pH
Kept at an optimum level to ensure enzymes and microorganisms function effectively.
Oxygen
Provided via an air inlet and distributed by stirring for aerobic respiration.
Nutrient supply
Required for growth and reproduction.
Waste products
Must be removed as their accumulation can restrict growth.
Industrial fermenter with stirring paddle, water jacket, pH and temperature probes, filtered air inlet, and nutrient inlet
Diagram 1: An industrial fermenter. A large sealed container with a stirring paddle (impeller), a water jacket for temperature control, probes for pH and temperature, an air inlet with a filter, and a nutrient inlet.

Exam Traps

  • Do not say penicillin is made by bacteria — it is produced by fungi (e.g. Penicillium).

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