Enzymes that catalyse the breakdown of proteins and carbohydrates have long been added to washing powders to help remove stains from clothes and crockery at low temperatures. But these enzymes dissolve and break down during a wash and may be attacked by other components of washing powder, such as alkaline cleaning agents, rendering them useless.Since enzymes could, in theory, be used again, the way they are currently flushed down the drain after one use is very wasteful, says the German washing machine and dishwasher maker Bosch.
The company has come up with an alternative approach. It involves using enzymes during periods of a wash when the alkaline cleaning agents are not present and also preserves them for reuse. The trick, says the company, is to encapsulate the molecules in a polymer membrane that is permeable to washing liquids but impermeable to water. This allows them to carry out their job of catalysis without dissolving.
The polymer capsules are not added to the washing powder, but are instead held in a hollow container in separate part of the washing machine through which water is flushed during appropriate parts of the washing cycle. In this way a variety of enzymes for attacking different stains can used and reused wash after wash.
Read the full reusable enzymes patent application.
Justin Mullins, New Scientist contributor