Pyocyanin extraction - the comparison of typical organic solvents and ionic liquids

Pyocyanin is a pigment produced by Pseudomonas aeruginosa that recently gained importance as a valuable chemical. Most often, the method for its extraction is based on the use of chloroform, a recognized hazardous substance. Therefore, an efficient and more environment-friendly method is vital for further use. In this work, we compared different organic solvents and ionic liquid, choline bis(trifluoromethylsulfonyl)imide - [Chol][NTf2], as pyocyanin extractants. We assessed the extraction efficiency using  pyocyanin standard dissolved in a microbiological medium and extracted directly from the bacterial culture. The extracted pigment was subjected to the HPLC technique to confirm its quantity and identity. The results showed that only chloroform, dichloromethane, and ethyl acetate were useful for pyocyanin extraction among tested organic solvents. Extraction with chloroform was the most efficient method. Nevertheless, dichloromethane, cheaper and recognized as more environment-friendly than chloroform, is also suitable. Notably, the ionic liquid also could be favourable for the extraction process, exhibited antibacterial properties, and was separated from the pigment by adsorbing pyocyanin on clays and desorbing it with ethanol. We showed that extraction of pyocyanin can be led by using alternative extractants, i.e. dichloromethane or ionic liquid, and therefore be less hazardous for the environment and the user.