environmental control of metabolism 6

• Micro-organisms are used in biotechnologybecause of...

  • Adaptability
  • Ease of cultivation (easily grown)
  • Speed of growth
• Growth media

  Provides micro-organism with raw materials for biosynthesis and an energy source
• What micro-organisms can produce

  • All the complex molecules required for biosynthesis (e.g. amino acids, vitamins, fatty acids)
• Energy source

  Derived from chemical substrates or from light in photosynthetic organisms
• Conditions needed to culture micro-organisms

  • Sterility
  • Control of temperature
  • Oxygen levels
  • pH
• Fermenters

  Specially controlled to provide the conditions needed to culture micro-organisms
• Sterile conditions in fermenters

  • Reduce competition with desired micro-organisms for nutrients
  • Reduce the risk of spoilage of the product
• Phases of growth of microorganisms

  1. Lag phase (enzymes induced to metabolise substrates)

  2. Log/exponential phase (most rapid growth due to plentiful nutrients)

  3. Stationary phase (nutrients depleted, toxic metabolites produced)

  4. Death phase (toxic accumulation, lack of nutrients)
• Antibiotics

  Secondary metabolites that confer an ecological advantage by allowing micro-organisms to outcompete others
• Use semi-logarithmic scales in producing and interpreting growth curves
• Viable cell counts

  Counting only the living micro-organisms
• Total cell counts

  Counting viable and dead cells
• Only viable cell counts show a death phase where cell numbers are decreasing