New biobased-zwitterionic ionic liquids: efficiency and biocompatibility for the development of sustainable biorefinery processes

A new family of biobased-Zwitterionic Ionic Liquids (ZILs) have been synthetized starting from the renewable resource L-histidine natural amino acid and varying the length of the alkyl chains. These ZILs derivatives were firstly studied for their biocompatibility with different microorganisms including bacteria, molds and yeast. The obtained MIC values indicated that all the microorganisms were 5 to 25 times more tolerant to ZIL derivatives than the robust 1-ethyl-3-methylimidazolium acetate [C2mim][OAc] used as a reference. Modeling studies also revealed that the presence of the cation and the anion on the same skeleton together with the length of the N-alkyl chain would govern the biocompatibility of these neoteric solvents. Among the different synthesized ZILs, the N,N’-diethyl derivative has demonstrated to be a suitable eco-alternative to the classically used [C2mim][OAc] for efficient pretreatment of harwood sawdust leading to significative improvement of enzymatic saccharrification. In addition, up to 5% w/v concentration in the media culture, ZIL did not induce deleterious effect on fermentative yeast growth nor ethanol production.