Biological Impact of Ionic Liquids Based on Sustainable Fatty Acid Anions Examined with a Tripartite Test System

Abstract

Fatty acid-based ionic liquids (FAILs) are an emerging class of biodegradable ILs. Although long-chained FAILs in particular offer a promising alternative to problematic hydrophobic ILs in lubrication and extraction applications, recent studies have revealed the possibility of an anionic "side-chain length effect", which would adversely impact their ecofriendliness. This study therefore investigated the toxicity of FAILs with sidechain lengths between C 1 and C 18 and benign cations by applying a tripartite biological test system, including enzyme inhibition test, determination of virucidal activity against three model viruses, and bactericidal activity against 12 clinically relevant bacteria. Results do not confirm a general anionic "sidechain effect" with FAILs but rather demonstrate a diverse outcome depending on the biological test system employed. While Gram-negative bacteria and viruses were not affected by increasing FAIL anion alkyl chain length, medium-and long-chained FAILs exhibited pronounced effects at the enzyme level and on Gram-positive bacteria. While this study reinforces the necessity to establish a multilevel approach for the (eco)toxicological evaluation of FAILs, it also demonstrates a specific effectiveness of FAILs against enzymes and Gram-positive bacteria, which should be considered for possible future applications.

Enzyme entrapment, biocatalyst immobilization without covalent attachment

“…216,217 Cholinium ILs with different anions, for example amino acids, are emerging as a green and sustainable ionic liquid media for enzyme/protein stability and activity studies. 204,[217][218][219]220,221 Fatty acid [222][223][224][225] and lactam 226,227 based ionic liquids are also likely to significantly contribute towards the library of greener ILs for future industrial biocatalytic processes.…”

Biocatalysis in ionic liquids: state-of-the-union

“…ILs produced from readily available mixtures of long chain fatty acids (LCFAs), and tetraalkyl ammonium and phosphonium and dialkylimidazolium cations, similarly represent a family of hydrophobic bio-based and biodegradable FAILs with a reduced environmental footprint. 74,75…”

Application of Ionic Liquids for Chemical Demulsification: A Review

“…Bio-based ionic liquids (e.g., fatty acid ionic liquids) are considered as biodegradable ionic liquids with less or without significant toxicity [ 130 , 131 ]. They are made of natural-derived compounds, and their physical properties can be changed by manipulating their anion alkyl chain length.…”