Investigating enzymes used in laundry detergents

Apparatus and Chemicals :

For each group of students:

Access to a range of

• fabrics

• staining substances

• detergents – with and without enzymes

2 Provide portions of enzymes to add to known volumes of the detergent, or make up solutions of enzymes (protease only, lipase only, amylase only) in non-bio detergent. Students mix these to make enzyme cocktails, following their investigation plans. 

• water (including hot water)

• Beakers

• Stirring rods

• Thermometer

For the class – set up by technician/teacher:

• Non-bio detergent at a suitable dilution

1 A suitable dilution of detergent is around 5%, that is 5 cm3 of detergent per 100 cm3. This is calculated from the typical detergent pack suggestion of 100 cm3 of detergent in a medium soil wash and machines using around 20 litres of water for the wash cycle. 

• Enzyme preparations to add to the detergent

2 Provide portions of enzymes to add to known volumes of the detergent, or make up solutions of enzymes (protease only, lipase only, amylase only) in non-bio detergent. Students mix these to make enzyme cocktails, following their investigation plans. 

• Range of fabrics: cotton, linen, nylon, rayon, silk, wool

3 Web research into the source and nature of the fibres in different fabrics will reveal that some are plant products (varieties of cellulose fibres), some are synthetic polymers, and others are of animal origin (protein fibres). With their knowledge of enzymes, students should be able to work out which laundry enzymes are likely to have a negative effect on silk and wool. 

• Staining substances

4 Students may devise their own stains, but could include cooking oils, fresh grass, milk, egg yolk, chocolate sauce, rich gravy, fruit juice. Encourage students to be sparing in how they stain the fabric, especially if investigating fatty stains at low temperatures. 

Investigating Enzymes using laundry detergents

Jane = branded bio vs non branded bio detergent using undiluted Ribena, orange juice, cranberry juice, ketchup

Becky = bio vs non bio detergent (staining agent as Jane)

Equipment: 

• 2 x water bath @ 40 degrees

• Approx. 10x10cm material square for staining

• Pipettes/stirring rods or plastic spoons

• 150ml beakers x 3 per group (labelled  bio or non-bio or shop bio & Persil bio plus beakers labelled water)/

• OHP pens

• white tiles

• Detergents to be diluted to 5% prior to practical (50g to 1L per class - approx 50ml per beaker)