With a high degree of specificity and high catalytic efficiency, enzymes are considered as “green” catalysts for the synthesis and catalysis of complex organic compounds. With the discovery and engineering of new enzymes, more enzymes are commercially used in a variety of industrial production thus enabling ‘Green manufacturing process” as reality.
Despite the unique advantages, free, un-immobilized enzymes still have some disadvantages when used as catalysts such as low sensitivity and stability, difficulty in separating from reaction mixture, recyclabilty and sometimes high cost. To circumvent this challenge, Asymchem Laboratories (Tianjin) Co., Ltd. (SHE: 002821SZ; “Asymchem”) has been committed to the application of enzyme immobilization to provide a convient and efficicent way for the application of enzymes in industrial production.
Enzyme immobilization technology refers to the natural enzyme restricted or bound within a certain space or attached on a solid structure, designed to restrict the freedom of movement of an enzyme. Immobilized enzymes can be easily removed from the reaction mixture by filtration, making workup easier and can be reused many times to lower the production costs. What’s more, Asymchem technical group also successfully applied the immobillized enzymes in continuous production, in order to achieve continuity and automation of production with higher reaction efficiency.
Because each immobilization method has its own advantages for different substrates and conditions, there is no universal strategy for different enzyme targets for immobilization,, therefore the characteristics and application requirements and other factors of enzymes need to be considered to choose the right method or combine different methods. Among the many immobilization techniques, Cross-linking enzyme aggregate (CLEAs) is a carrier-free immobilization method which produces a stable aggregate through protein precipitation combined with the addition of crosslinking agents, yields immobilized enzyme with a higher mass load than enzymes fixed to the carrier. However, due to the fact that CLEAs are without carrier support, the resultant immobilized enzymes has disadvantages like small particle size, poor mechanical strength thus leading to possible clogging in the filtration and recovery process. In effect this becomes a handicap as it cannot be well dispersed in the reaction when used again.
The immobilization by covalent bonding has the advantage of irreversible binding of the enzyme and a carrier, thus preventing enzyme leakage and effectively improving reusability. However, in the process of covalent reaction, enzyme molecules are prone for conformational changes, resulting in decrease in activity and some time specificity.
It is also one of the common methods to absorb enzymes into porous structures. For example, commonly used porous, beaded resin can achieve a high load of enzymes if the enzyme is relatively pure. However, this may not be advantageous for some enzymes which are not pure enough or the purification may not be cost effective.
Asymchem has been committed in the field of bio-catalysis for many years and built an integrated enzyme engineering platform with an in-house enzyme library consisting of ~ 1000 kinds of enzymes. It aims to obtain suitable enzymes with high efficiency and stability for R&D and production of novel drugs at lower cost while ensuring environmental protection. Different immobilization methods have been developed by Asymchem to ensure the smooth and seamless transition of integrating immobilized enzymes in the production operation.
Case of transaminase immobilization
Depending on ketones as substrate and the choice of amine donor, transaminases can be used to produce enantiomer chiral amines, key intermediates in a number of pharmaceutical compounds that possess a wide range of biological activities. Asymchem has successfully used immobilization to solve a series of challenges such as low enzyme activity, high cost due to extensive enzyme use. In addition to that, Asymchem technical group has developed an approach to find the best immobilization method: Use directed enzyme evolution to improve its intrinsic properties like activity & stability and develop a new, improved transaminase mutant, then try different immobilization methods to find the best one. This combined effort at both areas of technology has resulted in the best immobilized Transaminase.
Immobilization of enzyme make it possible to reuse the enzyme many times and improve the conversion rate. Moreover, Asymchem technical team also tried the application of immobilized enzyme in continuous reactions. For example, in the continuous reactions using packed bed reactors (PBR) and continuous stirred-tank reactors (CSTR), enzyme activity did not decrease after repeated use for a long time. Compared with the traditional batch reaction, the reactor production capacity is increased by 7 to 14 times. After exploring and screening of different methods, Asymchem successfully solved the limited application of bio-catalysis technology and the immobilized transaminase it developed can be effectively used in production.
Enzyme immobilization technology has been applied in many fields such as pharmaceutical manufacturing, food industry, bioremediation and bio-sensing. Further progress will be made in a variety of innovative immobilization technologies, with the rapid development of emerging technologies such as nanotechnology and integrated systems engineering. With years of commitment in the field of bio-catalysis, Asymchem will make continued efforts to improve the integrated enzyme engineering platform, with an aim to provide custom biotransformation solutions and promote the “eco-efficient, green” manufacturing practice in the pharmaceutical industry.