Introduction

In this article we look at the use of immobilized enzymes in industrial manufacture and the benefits they offer to create a more eco-sustainable and efficient process.

The use of enzymes in industrial manufacture has seen a growth in popularity in recent decades due to their advantages over more traditional chemical processes. Compared to synthetic catalysts, enzymes demonstrate high specificity, lower energy requirements and improved sustainability when performing chemical transformations. However, immobilizing these green catalysts on solid supports can offer an increased stability to operating conditions and in certain cases, a simplified process. Therefore, the increasing use of immobilized enzymes in the industry is offering a solution to the growing pressures for greener manufacturing.

Use of Immobilized Enzymes in Industrial Manufacturing

The use of immobilized enzymes in industrial manufacturing is increasing in many different sectors such as pharmaceutical, chemical and food. Thanks to major achievements made in enzyme development and protein engineering in recent years, more and more molecules are being synthesized using enzymes.

Immobilization of an enzyme combines the selectivity, stability and kinetic of that enzyme with the physical and chemical properties of the carrier in a specialized formulation. This has the primary role of maximizing the stability, both physical and enzymatic, of the biocatalyst. Immobilization also enables the recovery and reuse of the biocatalyst which has been facilitated by the developments in enzyme immobilization.

Figure 1 - Factors affecting enzyme immobilization

Benefits of Using Immobilized Enzymes as an Alternative to Chemical Processes

Immobilized enzymes provide substantial benefits to the industrial processes in which they are currently used. These benefits include: process simplification, reduced environmental impact and a more sustainable process compared to chemical synthesis.

For all enzymes, the possibility to be immobilized and used in a heterogeneous form brings important industrial and environmental advantages, such as simplified downstream processing or continuous process operations.

Compared to chemical catalysis which uses high temperatures, expensive catalysts, toxic reagents and by-products are formed, the use of enzymatic catalysis offers the possibility to work in a 'greener' condition.

Enzymes are highly regio- and enantioselective and often this is the key to their success. Molecules produced using enzymes are cleaner and have the desired enantiospecificity. When they are in the immobilized form, they have these additional benefits:

  • Possibility to use equimolar concentration of substrates
  • Obtain an enantiomeric excess, usually much higher than chemical catalysis
  • Use relatively low temperatures (< 80°C)
  • Possibility to use organic solvents
  • Use various process configurations such as column, batch or expanded bed reactors
The choice to use enzymes in their immobilized form depends on the evaluation of costs associated with their use, versus benefits obtained in the process.

Case Study: Sitagliptin Manufacture for Pharmaceutical Applications

A good example of protein engineering coupled to a successful enzyme immobilization is the use of engineered transaminase for sitagliptin manufacture. This enable the transition from a chemical process to a green process.

This case study has been taken from 'Industrial Applications of Immobilized Enzymes - A Review' by Dr. Alessandra Basso and Dr. Simona Serban. Find the full article here.

Method

The initial enzyme development using a combination of modelling and directed evolution led to an active and stable R-selective amine transaminase for the synthesis of sitagliptin, a key blockbuster from Merck for the treatment of diabetes.

The use of organic solvents is necessary to increase the poor solubility of sitagliptin, therefore, the use of non-immobilized transaminase limits the choice of solvents making the downstream processing difficult. Using immobilized transaminase opens the possibility to use neat organic solvents and recycle the immobilized transaminase without loss of enzyme activity.

Findings

This is an excellent example of the success of a combined approach to enzyme engineering and process optimization using immobilized enzymes.

Merck reported conversions of >80% in isopropylacetate with very high substrate concentration at 60°C. This approach was able to replace a chemical process based on hydrogenation of enamine at high pressure; the biocatalyzed process gave 99.5% enantiomeric excess and was able to convert very high concentrations of prositagliptin in the final product, using an immobilized enzyme in the presence of DMSO as a cosolvent.

The final mutant enzyme was able to not only perform the desired reaction with high yields, but also to tolerate high denaturing solvent concentration, to work in extremely high concentrations and to be immobilized for recycling purposes.

Conclusion

The real-world applications of immobilized enzymes in industrial manufacturing are making a considerable case for their implementation into processes as an alternative to chemical catalysis. Immobilized enzymes have demonstrated a host of benefits to all aspects of industrial manufacturing from reducing environmental impact to creating a more sustainable process.

Purolite Healthcare & Life Sciences' Lifetech™ range of immobilized enzymes and enzyme immobilization resins was designed to meet the needs of manufacture in the food, chemical and pharmaceutical industries. Available in a wide range of particle sizes for varying applications, the Lifetech™ range is the largest enzyme immobilization product library in the world.

View the products here