Enzymes have been used in biotechnology for millennia. Without realising it, ancient Egyptians and Babylonians used the enzyme systems of yeast to make bread and brew beer. Recently purified enzymes have been used..

Enzymes are useful for a number of reasons:

• They are catalysts so the make reactions easier. This increases productivity and yield

• As catalysts they are not consumed by the reaction. The may be used over and over again

• Enzymes show specificity to the reaction they control

• Enzymes are sensitive to their environment so they can be controlled by adjusting the temperature, the pH or the substrate concentration

Some examples of enzymes used in biotechnology

Lactase

Lactase is used to remove the sugar lactose from milk and other dairy products.

Lactose intolerance

Some people are intolerant of lactose in milk they cannot digest it.
The lactose remains in the digestive system and is fermented by bacteria.
The result is nausea, cramps, bloating, gas, and diarrhea occurring 30min to 2h after consuming milk products (not just milk but ice cream, some cheeses, soups or even salad dressings).
The treatment includes taking a tablet of lactase enzyme with a meal. The lactase digests the lactose in the food.

References:

National Digestive Diseases Information Clearinghouse
Medline plus

Source: Lactase enzyme (β-galactosidase) is extracted from fungi such as Aspergillus oryzae.

Ref: Wikipedia

Substrate: Lactose

Reaction

This is a hydrolysis reaction

Advantages:

Lactose intolerance around the world:

Most children are tolerant to lactose up to the age of 2 years. From that point on in many peoples the synthesis of lactase enzyme in the digestive stem diminishes and they become lactose intolerant. Tolerance to lactose into adulthood seems to reflect a cultural dependence on dairy products.
Most modern Western Europeans and people of European ancestry, Mongols and certain African tribes (e.g. the Fulani of West Africa) show lactose tolerance into adulthood.
Most modern East Asians, sub-Saharan Africans and native peoples of the Americas and Pacific Islands are intolerant as adults.
The difference is due to a mutated gene which maintains lactose synthesis in the digestive system into adulthood.

Glucose oxidase (GOD or GOx)

Used in glucose testing strips for diabetics. The diabetic can test themselves simply by pricking their finger with a sterile needle and placing a drop of blood on the end of the test strip.

The pastel at the end of the strip contains the two enzymes (one is GOx) and a dye.

Source: The mould Aspergillus niger

Substrate: Glucose
This enzyme also requires Flavin Adenine Dinuleotide (FAD) as a cofactor

Advantages
Specific to glucose, the blood sugar
Cheap
Reliable
Permits patients to test their own blood glucose

Pectinase

Some fruit juices (e.g. lemon juice and black current juice) sell more easily if they are transparent solutions. Raw fruit juice is cloudy. This cloudiness is caused by insoluble pectins (large polysaccharides). Pectinase is used to remove the cloudiness.

Source: Fungi such as Aspergillus

Pectinase is in fact a mixture of enzymes

Substrate: Pectins

Optimum pH: 5

Optimum temperature: 45 to 55°C

Advantages

Clears the fruit juice making it more saleable
Increases the amount of juice draining from the pulp (Up to 20% more)