Effect of temperature on the enzymatic activity of lactase in breaking down lactose


  • Ellen Choi
  • Madeline Dow
  • Helia Jafari
  • Vani Sharma


This study was conducted to test glucose production in the first order reaction of lactose
hydrolysis with the help of the enzyme β-galactosidase (lactase). Lactose is a disaccharide naturally
found in most mammalian milk and is composed of the two monosaccharides glucose and galactose
(Buller & Grand, 1990). This experiment tested the effect of temperature on the enzymatic activity of
lactase by measuring the glucose concentration of lactose over time. A standardized curve was created to
account for discrepancies between the actual glucose concentrations and the readings from the
OneTouch Ultra 2® blood glucose meter. Lactaid® Extra Strength pills containing lactase were dissolved
in solution and added to 50 mmol/L lactose. Glucose concentrations were measured every 5 minutes
across a 45 minute interval to calculate the reaction rates of lactose hydrolysis at 22ºC and 37.5ºC with
enzyme catalysis. Reaction rate graphs were created to compare the breakdown of lactose at the two
temperatures, and rate laws for the reactions with the two treatments were determined. From the rate
laws, the reaction of lactose hydrolysis at 22ºC produced a rate constant of k = 0.0109s-1, and the group
that received a treatment of 37.5ºC produced a rate constant of k = 0.0150s-1. Ultimately it was shown
that at a higher temperature, reaction kinetics were higher as expected. From this it was concluded that
the human body is at an optimal temperature for the breakdown of lactose.