From protein engineering to immobilization: promising strategies for the upgrade of industrial enzymes

Abstract

Enzymes found in nature have been exploited in industry due to their inherent catalytic properties in complex chemical processes under mild experimental and environmental conditions. The desired industrial goal is often difficult to achieve using the native form of the enzyme. Recent developments in protein engineering have revolutionized the development of commercially available enzymes into better industrial catalysts. Protein engineering aims at modifying the sequence of a protein, and hence its structure, to create enzymes with improved functional properties such as stability, specific activity, inhibition by reaction products, and selectivity towards non-natural substrates. Soluble enzymes are often immobilized onto solid insoluble supports to be reused in continuous processes and to facilitate the economical recovery of the enzyme after the reaction without any significant loss to its biochemical properties. Immobilization confers considerable stability towards temperature variations and organic solvents. Multipoint and multisubunit covalent attachments of enzymes on appropriately functionalized supports via linkers provide rigidity to the immobilized enzyme structure, ultimately resulting in improved enzyme stability. Protein engineering and immobilization techniques are sequential and compatible approaches for the improvement of enzyme properties. The present review highlights and summarizes various studies that have aimed to improve the biochemical properties of industrially significant enzymes.

Figure 1

Evolvable enzyme properties for its successful utilization in industrial processes.

Figure 2

Schematic representation of protein engineering strategies. Engineering method should be selected on the basis of the structural and mechanistic information and the feasibility of a high-throughput screening (HTS) system for screening or selection.

Figure 3

Immobilization of enzyme via different routes.

Figure 4

Enzyme stabilization by immobilization introduces additional covalent and non-covalent forces to an external matrix. (A) Non-covalent physical adsorption of an enzyme on the nanoparticle; (B) covalent binding of an enzyme to the nanoparticle (multipoint attachment); (C) covalent crosslinking of enzymes; and (D) microencapsulation of an enzyme by a micelle.