Enzymes—Catalysts for Life
Dr. Muhammad M. Chaudry, President
Enzymes are proteins that act as catalysts, driving chemical reactions in the cells of living organisms. Some enzymes result in very quick reactions while others enable reactions to take place under more mild conditions. Enzymes can be very specific affecting only one type of reaction or more general having a wider effect.
With all the reactions occurring in living cells, there are many enzymes required to catalyze all the reactions. To date, over 1500 enzymes have been identified.
Many of the bodily functions must occur very quickly. Enzymes play a role in speeding up the chemical reactions, enabling the body to react with the speed required. An example is the exhaling of carbon dioxide. Carbon dioxide is formed in the living cells of the body and must be transported from each cell to the lungs where it can be removed and exhaled. The blood provides the transport mechanism. However, to enter the blood stream, the carbon dioxide must be hydrolyzed. An enzyme, carbonic anhydrase, catalyzes this reaction so that carbon dioxide can be removed from the body. In fact, the enzyme works so fast, the hydrolysis occurs 10 million times faster than without the enzyme. This enables the body to keep up with our breathing.
The hydrolysis of some sugars requires very high temperatures. Enzymes enable this reaction to proceed at lower temperatures. This is a very important aid to the human body, which is maintained at a relatively low temperature.
With the many reactions occurring in the living cell, enzymes must be very specific to avoid affecting other vital reactions. Reactions that are catalyzed by enzymes rarely produce any by-products. This is very important within the body and is very useful in industrial applications.
Enzymes have been used for many centuries. There is evidence of the use of enzymes in cheese making dating back to 800 BC. The modem history of enzymes goes back to the 1800’s. During that time, enzymes such as yeast and diastase were discovered. As catalysts, enzymes are not used up. Rather they react and then are released again to remain in the system.
On an industrial level, enzymes are used for many purposes and in many industries. We are aware of the use of enzymes in the food industry for cheese making, baking and fruit and vegetable processing. Enzymes are also used in the production of sugar, the processing of starch, the hydrolysis of proteins and the modification of oil and fat. Other uses include brewing and winemaking, detergent production, the textile industry, the pulp and paper industry and in personal care-products. Actually most enzymes are used in non-food related applications. With so many enzymes, the International Union of Biochemists developed an identification system to classify enzymes. Naming of enzymes involves a numerical classification, a long systematic name and a short, easy to use name. For example, the enzyme that catalyzes the conversion of lactose (milk sugar) to galactose and glucose is classified as EC 220.127.116.11, has the systematic name beta D-galactoside galactohydrolase and the easier name lactase.
Enzymes have been classified into 6 categories.
Oxioreductases – these enzymes catalyze oxidation reactions, such as the conversion of alcohol.
Transferases – these enzymes catalyze the transfer of a group of atoms, referred to as a radical) from one molecule to another, such as the transfer of amino groups.
Hydrolases – these enzymes catalyze the reaction of chemical with water. This usually breaks up large molecules into smaller ones, such as the hydrolysis of proteins.
Lyases – these enzymes catalyze reactions producing in or resulting double bonds. An example of this is the conversion of sugars.
Isomerases – these enzymes catalyze the transfer of groups on the same molecule, resulting in a new structure to the molecule.
Ligases – these enzymes catalyze the joining of molecules to form larger molecules. These reactions normally require the energy to proceed.
The identification and understanding of DNA led to gene-splicing and the development of bio-engineered enzymes. In fact, many enzymes are now produced using bioengineering. With the large demand for enzymes, industrial production has evolved to use different methods for the growth and production of enzymes. One such method of production is submerged fermentation. In this process, selected microorganisms (bacteria and fungi) are grown in closed vessels in the presence of liquid nutrients and oxygen. As the microorganisms break down the nutrients, they release enzymes into the solution. The nutrients are normally sterilized items like maize starch, sugars and soya grits. The process can be operated continuously or in a batch mode. The temperature of the vessels and the oxygen consumption and pH are carefully controlled to optimize enzyme production.
Recovering the enzymes, referred to as harvesting, is done in a number of steps. First, the solids, referred to as biomass, are removed by filtration or centrifugation. The enzyme remains in the solution, called the broth. Then the broth is evaporated to concentrate the enzymes. The remaining material is filtered or crystallized. When required for research, the enzymes are further purified by ion exchange. The enzymes can be made available as powders, liquids or granules. The biomass is stabilized by lime treatment and used as fertilizer.
Enzymes are used in a number of food products. The first major use of enzymes developed in the 1960’s. Glucose production used to involve the acid hydrolysis of starch. The enzyme glucoamylase was developed to allow starches to break down to glucose. While the acid hydrolysis production method produces the desired product, the use of the enzymatic process reduces production costs, waste and by-product production. Today, almost all glucose is produced using enzymes. In fact starch processing is the second largest market for enzymes. The detergent industry is the largest market. High fructose syrup, which is found in most soft drinks, is also produced using an enzyme.
In the baking industry, enzymes help improve bread quality, freshness and shelf life of breads and baked goods. They convert sugars to alcohol and carbon dioxide, causing the dough to rise; strengthen the gluten network, resulting in greater flexibility and machinability; and modifying the triglycerides resulting in larger loaf volumes.
In cheese making, enzymes help the milk to coagulate, the first step in making cheese. In the dairy industry, both microbial and animal enzymes are used. Enzymes are also used to accelerate cheese ripening and to reduce the allergic properties of dairy products. Chymosin is the enzyme used for coagulation, lipase is used for ripening and lactase is used to improve digestibility. Of course, the source of the animal enzymes is a concern for Halal consumers.
Protein hydrolysis is another application for enzymes. Animal and vegetable proteins are hydrolyzed using enzymes to improve functionality and nutritional values of these proteins. Proteins are used in foods as emulsifiers, hydration agents, to control viscosity, as gelling agents and to improve cohesion, texture and solubility. The production of these proteins using chemical reactions is undesirable because it requires severe conditions and produces many by-products, which are difficult or expensive to remove. Enzymes are faster, allow production under milder conditions and produce fewer by-products Enzymes can be tailored to catalyze a specific reaction, with very low by-product formation. Enzymes can be used to produce meat extracts from scrap-bone residues. These are used in soups, sauces, broths and other applications.
In the juice industry, enzymes increase yields and improve color and aroma. Enzymes are used to clarify citrus juices, extract essential oils and the extraction of turbid extracts from citrus peels. Enzymes can also increase the amount of fruit pieces that remain intact when used in food products, such as fruit flavored yogurt.
Enzymes can be used in the extraction of vegetable oil. Oil is produced by pressing rapeseed, coconut, sunflower seed, palm kernels and olives and then extracting the oil using an organic solvent. Enzymes can be used to allow the oil to be extracted into a water solution, avoiding the need for the organic solvent. This is a more environmentally friendly method of producing oils. The method is not yet in wide use. Enzymes are also used to modify oils to improve nutritional value or to produce lubricants and cosmetic ingredients.
Enzymes are also used in winemaking and brewing. To summarize, enzymes play a vital function in the regulation and performance of living cells. They speed up reactions and catalyze specific reactions while producing few by-products. The food industry has taken advantage of these properties to produce enzymes that can reduce food production costs, manufacturing time, waste production and to improve taste, color and texture. The advent of bioengineering has enabled the enzyme industry to produce microbial enzymes that look and function like animal or vegetable enzymes. The bioengineered enzymes are cheaper to produce and it is easier to control the purity of the enzymes.
Enzymes have found uses in many industries and applications. In the food industry, the major uses of enzymes are in the baking, dairy, juice and ingredient industries. The use of microbial enzymes is more compatible with Halal food production, as it eliminates the use of animal derived enzymes. However, animal derived enzymes are still used in the food industry, particularly in the dairy industry. Cheese and whey produced using animal enzymes are haram if the source is non-Halal animals or Halal animals not processed according to Islamic requirements. Since whey is found in many non-dairy products, the use of animal derived enzymes to produce whey poses a big problem for the Halal consumer.
IFANCA has certified a number of enzymes for use in the food and cosmetics industries. This includes enzymes produced by Chr Hansen A/S (Denmark) Chr Hansen GmbH (Germany), Chr Hansen Inc. (USA), Genencor International (USA), Novozymes A/S (Denmark), Novozymes North America Inc. (USA), Norojymes (China) Rhodia, Inc. (USA), Valley Research Inc. (USA), Wuxi Syder Bio-Products Co., Ltd. (China) and others.