Fermentation of glucose

Fermentation of glucose

ZIMSEC O Level Combined Science Notes: Experiment: Determining the best conditions for the production of ethanol

Aim: To determine the best conditions for ethanol production

Materials: 5% glucose solution, 20% glucose solution, yeast, sodium hydroxide solution, mealie meal, dilute hydrochloric acid, thermometer, conical flask, cork, glass tube, test tube, lime water

Method

  1. Set up the apparatus as shown above
  2. Each student can use a different set of conditions
  3. 50cm3 of 5% glucose, yeast at room temperature
  4. 50cm3 of 5% glucose, yeast at 30°C
  5. 50cm3 of 20% glucose, yeast at room temperature
  6. 50cm3 of 5% glucose, yeast 10cm3 dilute acid
  7. 50cm3 of 5% glucose, yeast, 10cm3 of sodium hydroxide to make the solution alkaline
  8. Observe the rate at which carbon dioxide is produced

Observation and results

  • The most bubbles were observed from the test tube with 50cm3 of 5% glucose and yeast at 30°C
  • Very few bubbles where observed with 50cm3 of 5% glucose and yeast at room temperature
  • Adding an alkaline solution of sodium hydroxide stops the bubbles from forming
  • Increasing the temperature increases the rate at which Carbon Dioxide is evolved
  • Increasing the concertration of glucose increases the rate at which carbon dioxide is produced
  • Lowering the pH (by adding an acid) increases the rate at which the fermentation process takes place

Conclusion

  • The best conditions for the fermentation are when the pH of the glucose solution is lower, the concentration of the glucose high and the temperature around 30-40°C

To access more topics go to the Combined Science Notes page.


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