Recent applications of ionic liquids in biocatalysis

Abstract

The use of biocatalysts has become a real and competitive alternative to traditional chemical catalysts, contributing to the design of more environmentally friendly processes. However, depending on the enzymatic reaction mechanism, and particularly in nonaqueous reactions, the extensive use of organic solvents is required, which results in some drawbacks, such as low biocatalyst activity, loss of solvents to the atmosphere, and toxicity to the environment and human health. At the same time, the growing search for novel biobased products continues to be the inspiration for new biocatalysts and alternative reaction media. In the latter field, ionic liquids (ILs) have emerged as promising solvents or cosolvents in nonaqueous biocatalysis. The structure of ILs can be easily manipulated by changing the cation and/or anion (designer solvent capacity) and, thus, ILs can be designed to enhance the solubility of reagents and products and/or improve the activity and stability of enzymes. The designer solvents characteristic of ILs allow their use as tailored and highly suitable IL solvents in a wide range of enzymatic reactions. Moreover, this characteristic of ILs can be used in surface modifications of enzymatic supports to improve enzyme immobilization, activity, and reuse. Thus, the use of biocatalysts in IL-based media has become a competitive alternative to traditional chemical catalysts, contributing to the design of more environmentally friendly processes. In addition, the increasing search for novel biobased products inspires new biocatalysts and alternative reaction media. This chapter presents an overview on emerging applications of ILs in the biocatalysis field, namely on their use as solvents or cosolvents and as surface modifiers (supported ionic liquids) for enzyme immobilization. Recent and relevant examples (since 2015) carried out in nonaqueous media have been selected and highlighted, such as their use in biomass pretreatment, lignin valorization, biofuel production, biosensors, and bioremediation.