Although enzyme immobilization began over 100 years ago, it remains one of the most essential industrial technologies today. This is because immobilized enzymes are highly versatile and have a wide variety of potential applications. Also, the enzyme immobilization process has been slowly perfected over the years, making it much simpler, quicker, and efficient than ever before. This has served as another motivating factor to utilize this process.Although enzyme immobilization began over 100 years ago, it remains one of the most essential industrial technologies today. This is because immobilized enzymes are highly versatile and have a wide variety of potential applications. Also, the enzyme immobilization process has been slowly perfected over the years, making it much simpler, quicker, and efficient than ever before. This has served as another motivating factor to utilize this process. These days, EI has become intricately involved in industrial processes that are based on biotransformations. It has also become a vital element to cutting-edge technologies, such as genetic engineering and much more. With that in mind, let's take an in-depth look at enzyme immobilization and why it's important.
What are immobilized enzymes?Before delving into the importance of enzyme immobilization, let's take the time to understand exactly what immobilized enzymes are. Simply put, an immobilized enzyme is an enzyme that is attached to a material that is insoluble and inert. Immobilizing an enzyme allows for an increased resistance to variables such as temperature or pH. It also allows the enzymes to be stationary throughout the process, which makes it much easier for them to be separated and reused. Nevertheless, the qualities of the enzymes produced, largely depend upon the carrier type and the process used to immobilize them. The most common processes are adsorption, entrapment/encapsulation, cross-linking, or covalent bonding. The breakdown of these methods are as follows:
AdsorptionAdsorption is one of the simplest and quickest methods of reversible enzyme immobilization. This method involves a variety of non-covalent interactions. Once enzymatic activity grows stagnant, these enzymes can be gently removed from the support, so the support can be regenerated and attached to a new enzyme. This can help eliminate costs associated with the use of support materials. The process can be completed by immersing the carrier in an enzyme solution, so it can be adsorbed physically. Alternatively, the protein may be dried on an electrode surface. Either way, this method is often preferable because it is inexpensive to complete and does not require the use of an activation reagent. Moreover, the other main benefit of this method is that it promotes easy contact between the enzyme and the support. Also, there are typically minimal conformational changes made to the enzyme because the immobilization occurs in just a few minutes. This leads to high immobilized molecule activity retention. While there are many advantages to using this method, there are also disadvantages to consider. For instance, the method is known for promoting weak links between the carrier and enzyme, which causes substrate contamination. Also, certain support materials can lead to enzyme denaturation.
EntrapmentOn the other hand, the entrapment method involves covering or caging the enzymes in materials such as polymers, polymer/sol-gel composites, sol-gels, and other inorganic materials. Much like the adsorption method, this method is favored because it is inexpensive. It also allows for increased mechanical stability and makes for easy contact between the substrate and enzyme. However, unlike the adsorption method, this process is irreversible. There are disadvantages to using this method, as well. Namely, the small matrix pores size reduces the mass transfer of substrate to enzymes. Another disadvantage is the fact that big pores allow for carrier leakage. Moreover, this process also promotes low loading capacities and material abrasion. However, this can be solved by cross-linking.
Cross-linkingCross-liking is a lesser mentioned, irreversible method of enzyme immobilization. Also known as copolymerization, this process does not require the use of support as a means of preventing the loss of enzymes into the substrate solution. Also known as carrier-free immobilization, in this method, the enzyme essentially acts as its own carrier. This helps to eliminate all of the advantages and disadvantages associated with the use of various carriers. Most notably, it eliminates the likelihood that the carrier will cause activity to become diluted. This method is simple and inexpensive and is widely used in industrial and commercial preparation applications. However, the disadvantages lie in the fact that the enzymes being used are often not pure. Also, the reagents used are known for modifying the enzyme, which can lead to a loss in general catalytic properties.
EncapsulationThe encapsulation method involves enclosing the enzyme in a membrane capsule, which is made up of semi-permeable materials, such as nylon or cellulose. The overall effectiveness of this method is based on the stability of the enzyme being used. This method is advantageous because it is inexpensive and allows for large amounts of enzymes to be immobilized. However, the disadvantages of this method are that it that there is a limitation in terms of pore sizes and that only small substrate molecules are able to cross through the membrane.
Covalent bondingCovalent bonding is one of the most widely used methods of enzyme immobilization. This irreversible process involves covalently binding proteins to insoluble support materials. Formed between enzyme amino acid residues and functional groups of carrier surface, the covalent bonds formed using this method are known for being stable intra/inter-subunit bonds. This method makes it possible for the enzymes to be reused in more cycles than the other immobilization methods. This method also assists in the prevention of enzyme leakage in reaction environments. The results of this process are exceedingly pure and have an increased level of thermal stability. While this is, by far, the most favored method of enzyme immobilization, it also has a very notable disadvantage. In particular, this method of covalent bonding causes a decrease in enzyme movement and can also contribute to conformational changes. This can ultimately result in a loss of enzyme activity.
Benefits of using immobilized enzymesNow that you better understand what enzyme immobilization is, as well as the processes used, let's take a look at some of the benefits of using immobilized enzymes. They are:
- Reuse and recovery: One of the major benefits of enzyme immobilization is that it makes reusing and recovering enzymes a much simpler process.
- Cost-effectiveness: As already mentioned, using immobilized enzymes can be very cost-effective. This is because the ability to reuse enzymes saves money on things such as production, labor, space, and more.
- Versatility: Immobilized enzymes have a wide variety of potential applications.
- Consistent supply of products to the market: Since having the ability to isolate and reuse enzymes makes it possible to create products of all kinds, immobilized enzymes play a major role in various markets' abilities to keep certain products on the shelves and available to businesses and consumers.
- High enzyme-substrate ratio
- Process control improvement
- An increase in functional efficiency of the enzyme
- Less labor input
- Minimized reaction time
- Reduced opportunities for contamination in products created