One-step salting-out extraction of bacteriophage from its infection broth of Acinetobacter baumannii

Phages as a potential alternative antibiotic for multidrug-resistant bacterial infections are receiving great attention worldwide. However, the traditional separation and purification of phage are cumbersome, time-consuming, costly and inefficient. In this study, phage phiAB9 for multidrug-resistant Acinetobacter baumannii was separated and purified by a simple and cost-saving one-step salting-out extraction (SOE). Several kinds of salts and organic solvents without effect on phage survival were chosen to form the SOE systems, and the composition of SOE systems were optimized according to the phage recovery rate and impurity removal rate. After one-step SOE by an optimal system composed of 18% (w/w) ammonium citrate and 40% (w/w) ethyl acetate, the recovery rate of phage in the middle phase could reach to 90.82%, and most proteins (99.57%), cells (97.98%) and endotoxin (84.08%) were well removed, with a concentration factor of 210 and the purification factors of phage to proteins, cells and endotoxin were 303.64, 133.55 and 5.36, respectively. Comparing with two-step SOE and traditional aqueous two-phase extraction, one-step SOE may be an available method for the separation and purification of phages.