Learn More About Enzymes
Many chemical transformation processes used in various industries have inherent drawbacks from a commercial and environmental point of view. Non-specific reactions may result in poor product yields. High temperatures and/or high pressures needed to drive reactions lead to high energy costs and may require large volumes of cooling water downstream. Harsh and hazardous processes involving high temperatures, pressures, acidity or alkalinity need high capital investment, and specially designed equipment and control systems. Unwanted by-products may prove difficult or costly to dispose off. High chemical and energy consumption as well as harmful by-products have a negative impact on the environment.
All of these drawbacks can be virtually eliminated by using ENZYMES. Enzyme reactions are carried out under mild conditions, they are highly specific, involve very fast reaction rates, and are carried out by numerous enzymes with different roles. Industrial enzymes originate from biological systems; they contribute to sustainable development through being isolated from microorganisms, which are fermented using primarily renewable resources.
In addition, as only small amount of enzymes are required to carry out chemical reactions even on an industrial scale, both solid and liquid enzyme preparations take up very little storage space. Mild operating conditions enable uncomplicated and widely available equipments to be used, and enzyme reactions are easily controlled and can be stopped when the desired degree of substrate conversion has been achieved. Enzymes also reduce the impact of manufacturing on the environment by reducing the consumption of chemicals and energy, and the subsequent generation of waste.
Developments in genetic and protein engineering have led to improvements in the stability, economy, specificity and overall application potential of industrial enzymes. When all the benefits of using enzymes are taken into consideration, it’s not surprising that the number of commercial applications for enzymes is increasing every year.
Class of Enzyme Reaction Profile
1. Oxidoreductases :
Oxidation reactions involve the movement of electrons from one molecule to another. In biological systems we usually see the removal of hydrogen from the substrate. Typical enzymes in this class are called dehydrogenases.
2. Transferases :
This class of enzymes catalyses the transfer of groups of atoms (radicals) from one molecule to another. Aminotransferases or transaminases promote the transfer of an amino group from one amino acid to an alpha-keto-acid.
3. Hydrolases :
Hydrolases catalyse reactions between a substrate and water, and bind water to certain molecules. In this way, larger molecules are broken up into smaller units. This class of enzymes catalyses the cleavage of peptide bonds in proteins, glucosidic bonds in carbohydrates, and ester bonds in lipids.
4. Lyases :
Lyases catalyse the addition of groups to double bonds or the formation of double bonds through the removal of groups. Thus bonds are cleaved using a different principle to hydrolysis. Pectate lyases, for example, split the glycosidic linkages by beta-elimination.
5. Isomerases :
Isomerases catalyse the transfer of groups from one position to another on the same molecule. In other words, these enzymes change the structure of a substrate by rearranging its atoms.
6: Ligases :
Ligases join molecules together with covalent bonds. These enzymes participate in biosynthetic reactions where new groups of bonds are formed. Such reactions require the input of energy in the form of cofactors such as ATP.
The Nature of Enzymes
Enzymes are biological catalysts in the form of globular proteins that drive chemical reactions in the cells of living organisms. As such, they have evolved – along with cells – under the conditions found on planet Earth to satisfy the metabolic demands of an extensive range of cell types. In general, these metabolic demands can be defined as:
1) Chemical reactions take place under mild conditions
As the cells of nearly all animals, plants, and microorganisms can only function optimally within a fairly narrow temperature range, enzymes carry out chemical transformations under very mild conditions.
In order for this reaction to proceed non-enzymatically, heat has to be added to the maltose solution to increase the internal energy of the maltose and water molecules, thereby speeding up their collision rates and increasing the likelihood of their reacting together. The heat is supplied to overcome a barrier called ‘activation energy’ so that the chemical reaction can be initiated. As an alternative, the enzyme maltase can drive the same reaction at 25°C by lowering the activation energy barrier. It does this by capturing the chemical reactants – called substrates – and bringing them into intimate contact at ‘active sites’ where they interact to form one or more products. As the enzyme itself remains unchanged by the reaction, it continues to catalyse further reactions until an appropriate constraint is placed upon it.
2) Specific action according to enzyme class
To avoid metabolic chaos and create harmony in a cell teeming with innumerable different chemical reactions, the activity of a particular enzyme must be highly specific, both in the reaction catalysed and the substrates it binds. Some enzymes may bind substrates that differ only slightly, whereas others are completely specific to just one particular substrate. An enzyme usually catalyses only one specific chemical reaction or a number of closely related reactions. Unlike non-enzymatic chemical reactions, enzyme reactions rarely lead to the formation of waste by-products.
3) Very fast reaction rates
The cells and tissues of living organisms have to respond quickly to the demands put on them. Such activities as growth, maintenance and repair, and extracting energy from food have to be carried out efficiently and continuously. Again, enzymes rise to the challenge. They accelerate reactions by factors of at least a million. Carbonic anhydrase, which catalyses the hydration of carbon dioxide to speed up its transfer in aqueous environments like the blood, is one of the fastest enzymes known. Each molecule of the enzyme can hydrate 100,000 molecules of carbon dioxide per second. This is equivalent to ten million times faster than a non-enzyme-catalysed reaction.
4) Numerous enzymes for different tasks
Because enzymes are highly specific in the reactions they catalyse, an abundant supply of enzymes must be present in cells to carry out all the different chemical transformations required. Most enzymes help break down large molecules into smaller ones and release energy from their substrates. To date, scientists have identified over ten thousand different enzymes. Because there are so many, a logical method of nomenclature has been developed to ensure that each one can be clearly defined and identified. Although enzymes are usually identified using short trivial names, they also have longer systematic names. Furthermore, each type of enzyme has a four-part classification number (EC number) based on the standard enzyme nomenclature system maintained by the International Union of Biochemistry and Molecular Biology (IUBMB) and the International Union of Pure and Applied Chemistry (IUPAC). Most enzymes catalyse the transfer of electrons, atoms or functional groups. And depending on the types of reaction catalysed, they are divided into six main classes, which in turn are split into groups and subclasses. For example, the enzyme that catalyses the conversion of milk sugar (lactose) to galactose and glucose has the trivial name lactase, the systematic name beta-D-galactoside galactohydrolase, and the classification number EC 18.104.22.168.
Industrial enzymes are produced using a process called Submerged Fermentation. This involves growing carefully selected microorganisms (bacteria and fungi) in closed vessels containing a rich broth of nutrients (the fermentation medium) and a high concentration of oxygen (aerobic conditions). As the microorganisms break down the nutrients, they release the desired enzymes into solution. Thanks to the development of large-scale fermentation technologies, today the production of microbial enzymes accounts for a significant proportion of the biotechnology industry’s total output. Fermentation takes place in large vessels called fermenters with volumes of up to 1,000 cubic meters. The fermentation “Media” comprise of sterilized nutrients based on renewable raw materials like maize starch, sugars and soya grits. Various elementary salts are also added depending on the microbe being grown. Microorganisms into the fermentation medium secrete most industrial enzymes in order to break down the carbon and nitrogen sources.
Both batch-fed and continuous fermentation processes are common. In the batch-fed process, sterilized nutrients are added to the fermenter during the growth of the biomass. In the continuous process, sterilized liquid nutrients are fed into the fermenter at the same flow rate as the fermentation broth leaving the system, thereby achieving steady-state production. Operational parameters like temperature, pH, feed rate, oxygen consumption and carbon dioxide formation are usually measured and carefully controlled to optimize the fermentation process.