Biocatalysis and Biomass Conversion in Alternative Reaction Media

Abstract

In this Minireview, the state of the art in the use of ionic liquids (ILs) and deep eutectic solvents (DESs) as alternative reaction media for biocatalytic processes and biomass conversion is presented. Initial, proof-of-concept studies, more than a decade ago, involved first-generation ILs based on dialkylimidazolium cations and non-coordinating anions, such as tetrafluoroborate and hexafluorophosphate. More recently, emphasis has switched to more environmentally acceptable second-generation ILs comprising cations, which are designed to be compatible with enzymes and, in many cases are derived from readily available, renewable resources, such as cholinium salts. Protic ionic liquids (PILs), prepared simply by mixing inexpensive amines and acids, are particularly attractive from both an environmental and economic viewpoint. DESs, prepared by mixing inexpensive salts with, preferably renewable, hydrogen-bond donors such as glycerol and amino acids, have also proved suitable reaction media for biocatalytic conversions. A broad range of enzymes can be used in ILs, PILs and DESs, for example lipases in biodiesel production. These neoteric solvents are of particular interest, however, as reaction media for biocatalytic conversions of substrates that have limited solubility in common organic solvents, such as carbohydrates, nucleosides, steroids and polysaccharides. This has culminated in the recent focus of attention on their use as (co)solvents in the pretreatment and saccharification of lignocellulose as the initial steps in the conversion of second-generation renewable biomass into biofuels and chemicals. They can similarly be used as reaction media in subsequent conversions of hexoses and pentoses into platform chemicals.

Enzymatic Ring‐Opening Polymerization of Lactones: Traditional Approaches and Alternative Strategies

“…Ionic liquids (ILs) have emerged as promising alternative solvents due to their unique properties including negligible vapor pressure, low flammability, thermal and chemical stability, ability to dissolve many organic, inorganic, metallo-organic compounds, and polymeric materials. [108] ILs are organic salts, which are liquid at room temperature. Unlike the traditional solvents, ILs consist only of ions: large, asymmetrical, organic and heterocyclic cation (i. e., 1,3-dialkylimidazolium, tetraalkylammonium; 1,4-dialkylpyridinium, 1,1-dialkylpyrrolidinium, n-alkylpyridinium) and small, inorganic, or-ganic or complexes anions (i. e., hexafluorophosphate, tetrafluoroborate, trifluoromethyl acetate, bis[(trifluoromethyl) sulfonyl]imide, trifluoromethyl sulfate, chloride).…”

Preparative‐Scale Enzymatic Synthesis of rac‐Glycerol‐1‐phosphate from Crude Glycerol Using Acid Phosphatases and Phosphate

“…Consequently, the valorization of glycerol has gained increasing attention . Current applications involve the use of glycerol as an energy source and as a green solvent (e.g., as a component of deep eutectic solvents) . The main obstacle for the use of glycerol as a platform chemical is connected to the high input of energy required for its purification from the highly concentrated aqueous solutions obtained from biodiesel plants.…”

Proteomic profiling of Sporotrichum thermophile under the effect of ionic liquids: manifestation of an oxidative stress response

“…The exploitation of ILs is majorly in the area of biomass processing for the generation of second-generation biofuels (Hou et al 2017; Sheldon 2016). The lignocellulosic biomass is quite recalcitrant in nature due to the presence of cellulose component.…”