Ionic Liquid Toxicity in Biotechnological Yeasts: Experimental Assessment and Molecular Docking Insights

Ionic liquids (ILs) are promising media for biotechnological applications, although their use in microbial systems is limited by their toxicity to living cells and biomacromolecules. In this study, the toxicity profiles of selected IL-derived ions were evaluated toward Saccharomyces cerevisiae, Yarrowia lipolytica, and Kluyveromyces marxianus by determining the maximum non-toxic concentration (MNTC), and the experimental trends were further investigated through molecular docking against the corresponding yeast hexokinases. The results revealed a species-dependent response, with Y. lipolytica displaying substantially higher tolerance than K. marxianus and S. cerevisiae. For the anionic series, toxicity increased consistently from Cl^- to [NTf₂]^- in the three yeasts, with [NTf₂]^- showing the lowest MNTC values in all cases. The cationic series also showed clear differences in toxicity, though in a more species-dependent manner. Docking analyses revealed a strong qualitative relationship between binding affinity and MNTC, particularly for the anions, indicating that ions with more favourable interactions with hexokinase were generally tolerated only at lower concentrations. Thus, the results indicate that IL toxicity in yeasts emerges from the interplay between ion-specific properties and species-dependent structural features of the target enzyme. By integrating microbiological and computational analyses, this study provides new insight into the molecular basis of ion-dependent and species-dependent IL toxicity in yeasts of biotechnological relevance.