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Properties of Enzyme Lactase on Digestion of Lactose


The research demonstrates the action of an intestinal enzyme, lactase on the breakdown of lactose into glucose and galactose, and investigates the effect of temperature on enzyme activity


All metabolic reactions in an organism’s body are catalyzed by protein molecules called Enzymes. Enzymes are responsible for the ripening and rotting of fruits, etc. Digestion of food happens in the mouth, stomach and intestines, enzymes bring about this process. One such enzyme is Lactase, responsible for the breakdown of lactose, the milk sugar, into glucose and galactose.

Some adults lack this enzyme in their system hence milk products pass through their systems undigested till they reach the large intestine – therein lies a bacterial population that feasts upon lactose and digest it into glucose and galactose and large amounts of carbon dioxide causing flatulence. This flatulence may cause pain and discomfort to these individuals. Such people are known as Lactose Intolerant Individuals.

Biotechnology companies have produced Lactase-digesting aids like LACTAID or Dairy Ease, these predigest the lactose in the milk when the lactase enzyme is added to the milk before ingestion, thus facilitating normal digestion and absorption of glucose and galactose minus flatulence (Raunig, Lornie& William,1994). These are produced either as tablets or drops. This enzyme has been extracted from yeast found on wheat called Kluyveromyces lactis. Impregnated test strips like CHEMSTRIP uG to test for glucose in urine or other fluids has been used here, to semi-quantitatively measure the glucose concentrations from 100 to 5,000 mg/dl, i.e. (1 to 5% glucose); this will essay the presence of lactose in the milk by measuring the amount of glucose released when lactose is hydrolyzed to glucose and galactose.

Material required:

  • About four cups of milk for every eight teams.
  • A cup of juice.
  • Lactase enzyme drops (Lactaid).
  • Reagent strips for glucose analysis to show the concentration of glucose. These are the type used by diabetics to monitor glucose in their urine, and are available at most drug stores (Diastix is one brand) Note: These strips can be cut in half lengthwise to increase the number of reagent strips obtained from each container.
  • Small (10-25 ml) graduated cylinders, two for each team of students
  • Ice, A hot plate, hot pot, or another heating device.
  • A thermometer & Test tube racks for each student team


The team was divided into two. Each team was given two graduated cylinders and four test tubes, glucose reagent strips. These strips are coated with chemicals that change color in the presence of glucose. 10 ml of milk was measured into each of these test tubes, the measure of glucose was taken using the glucose testing strips. This reading was marked as the “Beginning Glucose Concentration”.

Then one test tube of milk was placed in ice, the second test tube at room temperature, the third was placed in a warm bath at 37˚C. And the fourth test tube was heated to 80 to 100 ˚C.

Two drops of lactase enzyme were dropped into each test tube. After 3 minutes a fresh reagent strip was used to measure the new glucose concentration of that solution. These readings were recorded as the “After Lactase, Glucose Concentration” on the Data Page. The tabulation of these readings was presented as a Graph presented herewith on the Data Page.

Data and observations

The following results have been obtained from the experimental protocol listed above. These measurements have been obtained for the enzyme lactase converting the disaccharide lactose found in milk into monosaccharides glucose and galactose. The glucose has been monitored by measuring with enzyme-based glucose test strips.

Temperature Glucose levels before lactase (mg/dL)
Glucose levels after lactase (mg/dL)
0 0C 0 50
20 0C 0 1000
37 0C 0 2000
100 0C 0 0

This experiment shows that lactase breaks milk down into glucose.


When the temperature boosts the molecules smash together, the kinetic energy of the molecules boosts, as a result, the rate of the chemical reaction increases. There is an optimum level until which the heat energy can rise and the chemical reaction takes place at the maximum rate. So it would be correct to say that as the temperature increases the rate of chemical reaction increases. As the number of hits on the binding sites increase and the probability of reaction increases (Hagar & Lornie, 1998). This happens up to the temperature of 37 0C any increase in temperature beyond this caused the cessation of reaction – as can be seen in the table when the temperature reached 100 0C the formation of glucose was zero. This is because the enzymes begin to denature or break down beyond this temperature – or more specifically at 50 ˚C. This proves that the optimum temperature for any enzymatic reaction to take place is 37 0C or the body temperature of all homeotherms.

Glucose levels after lactase (mg/dL) + LACTASE

 Temperature plotted on the X-Axis and the Glucose levels after lactase on the Y-Axis
Figure 1. Temperature plotted on the X-Axis and the Glucose levels after lactase on the Y-Axis

The above graph shows the Temperature plotted on the X-Axis and the Glucose levels after lactase on the Y-Axis. The level of glucose is at 50 mg/dL at 0 ˚C, the level of glucose formation rapidly increases from 0 to 20 ˚C and peaks at 37 ˚C. Then instead of rising further, it falls steeply between 37 to 100 ˚C. This is a graphical representation of the fact that the Enzymes, for that matter even Lactase lose their efficacy beyond 37 ˚C and denatures when heated beyond the threshold temperature of 50 ˚C. Hence when the temperature reaches 100 ˚C, the enzyme activity is seen as baseline or zero.

Denaturation is a method in which proteins or nucleic acids mislay their organization due to the pressure of exterior factors or chemical compounds such as an acid or alkali, a rigorous inorganic salt or heat. This mislay of arrangement directs to the collapse of vigorous spots and the whole arrangement of the molecule of the enzymes and making them nonfunctional. In many chemicals and enzymes, the process of denaturation is reversible like in the albumin of egg white, this happens when the denaturing influence is removed it could be heat, chemicals, pressure, etc. This led to the idea that all the information needed for proteins to regain their native state was encoded in the primary structure of proteins or that the template of the proteins was embedded in the DNA and the entire protein-making machinery of the organism hence the cellular machinery allows these molecules to be made again and again as and when the body requires.


  1. Raunig,V.,Lornie,B.,& William,H.(1994). Enzymes and the what and how of digestion. Science scope, 37-41.
  2. Hagar, W., & Lornie, B.(1998). Lactase staining of electrophoretic gels. The Science Teacher, 65 (n.d), 43-44.
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StudyKraken. (2022, August 25). Properties of Enzyme Lactase on Digestion of Lactose.

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"Properties of Enzyme Lactase on Digestion of Lactose." StudyKraken, 25 Aug. 2022,

1. StudyKraken. "Properties of Enzyme Lactase on Digestion of Lactose." August 25, 2022.


StudyKraken. "Properties of Enzyme Lactase on Digestion of Lactose." August 25, 2022.


StudyKraken. 2022. "Properties of Enzyme Lactase on Digestion of Lactose." August 25, 2022.


StudyKraken. (2022) 'Properties of Enzyme Lactase on Digestion of Lactose'. 25 August.

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