Nutrition & Digestion

Enzymes are also used in industry to speed up reactions outside the body. A common trick is to immobilise the enzyme so it can be reused.

What "immobilised" means

The enzyme is trapped inside small beads (typically beads of alginate, a jelly-like substance). The beads are then packed into a column. A liquid containing the substrate is poured through the column. The substrate diffuses into the beads, meets the enzyme, gets converted into product, and the product flows out of the bottom of the column.

The enzyme stays inside the beads and can be used again and again, instead of being washed away with the product.

Example: lactose-free milk

Many adults are lactose intolerant: they no longer make enough of the enzyme lactase, so the lactose (the sugar in milk) passes undigested into the gut and causes bloating, cramps and diarrhoea.

Lactose-free milk is made by running ordinary milk through a column packed with immobilised lactase. As the milk flows through, the trapped lactase splits the lactose into glucose and galactose, which are absorbed easily. The milk leaving the column is safe for lactose-intolerant people and tastes slightly sweeter, because glucose is sweeter than lactose. Because the enzyme stays in the beads, one column can treat milk continuously.