Q-309. Assessing the Effect of Ionic Liquids on Microbial Growth: New Concerns for Environmental Safety

C. McEntee1,2, P. Bisangwa1, M. Sahin2, X. Li3, J. Gwon3, J. Wishart4, S. Lall-Ramnarine3;
1Kingsborough Community Coll., Brooklyn, NY, 2Brooklyn Coll., Brooklyn, NY, 3Queensborough Community Coll., Queens, NY, 4Brookhaven Natl. Lab., Brookhaven, NY.

Ionic liquids (ILs), salts that are liquid at room temperature, are fast emerging as the solvents of choice in the chemical industry. Their relative non-volatility, non-flammability, wide liquid range and high conductivity make them serious candidates as green solvent alternatives to volatile organic solvents. In order to assess the relative safety of ILs, representative bacteria, fungi and algae were tested against ILs differing only in purity (as determined by color) and/or alkyl chain length. ILs were prepared identically with the exception of the reaction temperature. 10-fold serial dilutions (10mg/ml - 0.1mg/ml) were made and the MIC and MBC of each IL determined. Our results show that the purity of the IL is not a factor in toxicity and, as expected from previous reports in the literature, the size of the alkyl side chain is an important factor in determining IL toxicity. These studies also demonstrate that although the presence of a cell wall has no effect on the degree of toxicity, the presence and type of glycocalyx contributes significantly to IL resistance. Thus, P. aeruginosa was most resistant, K. pneumonia moderately resistant and E. coli, S. aureus and B. subtilis least resistant. The mold, Rhizopus stolonifer demonstrated sensitivity to the ILs on par with the bacteria. However, even at concentrations considered non-toxic, hyphal growth was altered. Results of the above studies were compared to an in vitro seed germination assay to determine which screen is most useful for identifying toxic ILs. 10-fold serial dilutions of ILs in MSR agar were made and alfalfa seeds plated. Results indicate the seed germination assay is several-fold more sensitive to the ILs than the microorganism assay; seeds failed to germinate at IL concentrations that did not inhibit growth of bacteria and fungi. These results raise concerns regarding the potential risk to microbial and plant ecosystems if ILs are released into the environment through effluent discharges or accidental spills.