Microbial Biocompatibility and Biodegradability of Choline-Amino Acid Based Ionic Liquids

Choline-Amino acid based ionic liquids (AAIL) have sparked recent interest throughout the scientific community due to their allegedly low cost and natural origin. They are considered as a potential “green” solvent to replace conventional volatile organic solvents. However, much is still scarce on their (AAILs) microbial toxicity and biodegradability. This study reports the synthesis of ten AAILs with cholinium cation and variable anions derived from amino acids. Their microbial biocompatibility to gram-positive (Bacillus licheniformis and Staphylococcus aureus) and gram-negative (Pseudomonas aeruginosa and Vibrio cholerae) bacteria and biodegradability by industrial sewage water were analyzed. All the tested AAILs were reported to have EC50 values in the range of 160-1120 mg/L which is deemed “practically harmless” based on hazard rankings. The toxicity trend was seen to reduce as the molecular weight of the anion decreased. The level of mineralization of AAILs through anaerobic microbial breakdown was found to be a factor of anion and its functional group in all the cases. They resulted to over 60% biodegradation in 28 days (readily biodegradable).