Enzymes in biotechnology and fermenters

Last time

Before we start: last time, in Plastics and eutrophication, you learned these points. Here they are again on one card. Keep them in mind, because today builds on them.

Cleaning, juicing, brewing

Your washing powder, your fruit juice and your lactose-free milk all contain enzymes. Enzymes from microorganisms are used in industry because they work fast and at mild temperatures. And to grow the microorganisms in bulk, factories use giant tanks called fermenters. Today: both.

Why use enzymes

Enzymes are biological catalysts. They speed up reactions without being used up. Each is specific to one reaction, and works at a mild temperature and pH, which saves energy and money. Many industrial enzymes are made by microorganisms, grown in fermenters.

Pectinase in fruit juice

Pectinase breaks down pectin, which holds plant cell walls together. The fruit pulp becomes softer, so more juice can be extracted. The juice is also clearer, because it has less cloudy pulp.

Pectinase at work

Here is pectinase working. The enzyme has an active site that fits only its substrate, pectin. It breaks the pectin into smaller molecules.

Protease and lactase

Biological washing powders contain protease, which digests protein stains such as blood and egg. Because the enzyme works at low temperatures, a cooler wash can be used, which saves energy. Lactase digests lactose to glucose and galactose, to make lactose-free milk for people who cannot digest lactose.

Fermenters

A fermenter is a closed vessel where microorganisms are grown on a large scale to make products. Examples: penicillin, an antibiotic from the fungus Penicillium, and mycoprotein, a meat substitute from a fungus. Enzymes and human insulin made by bacteria are also produced this way.

Conditions in a fermenter

Nutrients, such as glucose and minerals, are added so the microorganisms can grow and reproduce. Temperature and pH are kept at the optimum, using a cooling jacket and pH probes, for the best enzyme activity. Oxygen is supplied for aerobic respiration, and paddles stir the contents, so that everything mixes evenly. The vessel is sterile, so no unwanted microorganisms compete or contaminate the product.

Immobilised enzymes

An immobilised enzyme is fixed to beads or a surface, so the reactant flows past it. The product is not mixed with the enzyme, and the enzyme can be reused many times. This lowers the cost, and the enzyme is often more stable.