21.2 Biotechnology

2026 Syllabus Objectives

  1. Describe the role of anaerobic respiration in yeast during the production of ethanol for biofuels
  2. Describe the role of anaerobic respiration in yeast during bread-making
  3. Describe the use of pectinase in fruit juice production
  4. Investigate and describe the use of biological washing powders that contain enzymes
  5. Explain the use of lactase to produce lactose-free milk
  6. Describe how fermenters can be used for the large-scale production of useful products by bacteria and fungi, including insulin, penicillin and mycoprotein
  7. Describe and explain the conditions that need to be controlled in a fermenter, including: temperature, pH, oxygen, nutrient supply and waste products

Biofuels and Anaerobic Respiration in Yeast 🔋

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What are Biofuels?

Biofuel is a fuel made by mixing ethanol (produced through anaerobic respiration of yeast) with petrol. Ethanol is an alcohol that burns well, though it contains less energy per litre compared to fossil fuels.

Role of Anaerobic Respiration in Biofuel Production

Yeast cells carry out anaerobic respiration when oxygen is not available. During this process, glucose is broken down to produce ethanol and carbon dioxide:

glucose→ethanol+carbon dioxide\text{glucose} \rightarrow \text{ethanol} + \text{carbon dioxide}

The ethanol produced is the key product used in biofuels. This ethanol is then mixed with gasoline to create biofuel for vehicle engines.

Real-World Example: Brazil's Sugarcane Industry 🌱

In Brazil, sugarcane is used efficiently for biofuel production:

  • Sugarcane is processed to extract sugar
  • The leftover waste material is fermented by yeast
  • Anaerobic respiration produces ethanol from this waste
  • The ethanol is collected and mixed with petrol to create biofuel

Advantages of Biofuels ✅

Sustainability: Ethanol from plants is a sustainable resource that can be regrown, unlike fossil fuels which take millions of years to form.

Carbon Neutrality: Growing crops for fuel removes carbon dioxide from the atmosphere through photosynthesis. This balances the CO2\text{CO}_2 released when the biofuel is burned during combustion, making it more environmentally friendly.

Disadvantages of Biofuels ⚠️

Competition with Food Production: Using agricultural land for fuel crops instead of food crops can reduce food availability and increase food prices globally.

Loss of Biodiversity: Clearing natural ecosystems (such as rainforests) to create monoculture crop plantations for biofuel production reduces biodiversity and destroys habitats.

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