Interfacial behavior and extraction kinetics of phages in a salting-out extraction system of ammonium citrate and ethyl acetate

To fight the increasing emergence and spread of antimicrobial resistance, phages have regained much more interest as the potential substitute in recent years. Separation and purification of phages were developed by salting-out extraction (SOE) with advantages of simpleness, high efficiency, high yield and the easiness to scale-up over the traditional means. In this study, SOE system composed of ammonium citrate and ethyl acetate was used to investigate the partition behavior of phages, phase separation, and extraction kinetics. With the increase of phase volume ratio, the phage phiAB9 was progressively transferred from the bottom phase to the middle phase. Accordingly, the solubility and aggregation of the middle phase increased, and the color got darker. Furthermore, the phase inversion point was kept at phase volume ratio between 1.0 and 1.1, at which the phase separation time was the shortest. The extraction kinetics revealed that the partition behavior could be finished in 10 min without centrifugation. Finally, the SOE system was also viable alternatives for the isolation and purification of phage λ, phiKP1 and phiSM1. The mechanism of SOE process is very important for its application and scale up in phage separation.