Enzymes at Work: Food, Pharmaceutical and Other Industries

Enzymes in your fridge, your medicine cabinet and your laundry room

Check the ingredients on a block of Canadian cheddar and you may see "microbial enzyme". A carton of lactose-free milk says "lactase enzyme". Many laundry detergents boast that they contain enzymes. Each of those enzymes is doing a job you studied in the last few lessons: speeding up a specific reaction (usually a hydrolysis) under mild conditions.

Industry uses enzymes because they are specific (few unwanted side products), work at moderate temperatures and pH (saving energy), and are biodegradable. This lesson analyses those applications, especially in the food and pharmaceutical industries.

Enzymes in the food industry

• Cheese. Milk's main protein, casein, exists as tiny clusters that repel each other. Chymosin (rennin), traditionally from the stomachs of young calves as rennet, cuts one specific protein (κ-casein) on the cluster surfaces, so the clusters stick together into curds, leaving liquid whey. Much of the chymosin used today is made by microorganisms that carry the calf chymosin gene (fermentation-produced chymosin), so it is pure, consistent and doesn't require calves. Bacterial cultures add lactic acid and their own enzymes, which break down proteins and fats during aging to create flavour.
• Lactose-free milk. Lactase hydrolyzes lactose into glucose and galactose, so people with lactose intolerance can digest it (and it tastes sweeter).
• Bread. Amylases added to flour break starch into sugars that yeast can ferment, giving a better rise and a browner crust; other enzymes slow staling so bread stays soft longer.
• Fruit juice. Pectinases break down pectin in fruit cell walls, increasing the amount of juice pressed out and making it clear instead of cloudy.
• Sweeteners. Starch from corn is hydrolyzed to glucose by amylases; then glucose isomerase (usually immobilized) converts some glucose into fructose, which tastes sweeter, to make glucose-fructose syrups.
• Meat tenderizers contain proteases such as papain (from papaya) or bromelain (from pineapple), which hydrolyze muscle proteins.
• Brewing and baking with grains depend on amylases (from the grain or added) to turn starch into fermentable sugars.

Immobilized enzymes

In many processes the enzyme is immobilized: attached to the surface of beads, trapped inside a gel, or bound to a membrane, often packed in a column. The substrate solution flows through, and product comes out. Advantages:

• the enzyme is reused for days or weeks, which lowers cost;
• the product isn't contaminated with enzyme, so no purification step is needed;
• the process can run continuously;
• immobilized enzymes are often more stable at higher temperatures and over a wider pH range.

Disadvantages: setting up is expensive, some activity can be lost when the enzyme is attached, and substrate must reach the active sites through the support.

Enzymes and pharmaceuticals

Enzymes matter to medicine in four ways.

1. Making drugs. Enzymes can carry out one precise step in a complex synthesis, often producing only the correct stereoisomer. For example, the enzyme penicillin acylase is used to make the core of semi-synthetic penicillins such as amoxicillin, and an engineered enzyme is used in manufacturing the diabetes drug sitagliptin. This can replace steps that needed heavy metals, high temperatures or toxic solvents.
2. Enzymes as medicines. People with cystic fibrosis often take pancreatic enzyme capsules with meals because thick mucus blocks their own enzymes from reaching the intestine. Lactase tablets help people with lactose intolerance. Clot-dissolving enzymes (such as alteplase, also called tPA) are used in hospitals for some strokes and heart attacks.
3. Controlling how fast a drug acts. Some medicines are prodrugs: inactive until enzymes in the body convert them. Codeine, for example, is converted to morphine by a liver enzyme, and people vary in how much of that enzyme they make, which is one reason the same dose can affect people differently. Liver enzymes, especially the cytochrome P450 family, also break drugs down; this sets how long a dose lasts and how often it must be taken.
4. Drug interactions. If one substance inhibits a P450 enzyme, a second drug that is normally broken down by it can build up to higher levels. Grapefruit juice inhibits one of these enzymes in the intestine, which is why some prescription labels in Canada warn against it. This is enzyme inhibition (from Controlling Enzymes) with real consequences.

Enzymes also run many diagnostic tests: most blood-glucose test strips used by people with diabetes contain an enzyme (such as glucose oxidase) that reacts only with glucose.

Other industries

• Laundry and dish detergents contain proteases, lipases and amylases that digest food and body stains. Because they work at low temperatures, clothes can be washed in cold water, saving energy.
• Pulp and paper: enzymes called xylanases help bleach pulp, reducing the amount of chlorine-based chemicals needed.
• Biofuels: cellulases hydrolyze cellulose in crop wastes and wood into glucose, which yeast can ferment to ethanol.
• Textiles: enzymes give jeans a "stone-washed" look with fewer actual stones.

Weighing benefits and drawbacks

Benefits: high specificity and fewer by-products; lower temperatures and pressures (less energy); less use of harsh chemicals; biodegradable.

Drawbacks and concerns: enzymes can denature if conditions aren't controlled; some are expensive to produce and purify; airborne enzyme dust can cause allergies in factory workers (modern detergents use enzymes sealed in granules to reduce this); and many industrial enzymes are made by genetically modified microorganisms, which some people want labelled or avoided. Evaluating these trade-offs uses the same research skills as any scientific issue: reliable sources, evidence and clear criteria (A1.3, A1.9).