Aqueous two-phase systems for the recovery and purification of phage therapy products: Recovery of salmonella bacteriophage ϕSan23 as a case study

Contamination with Salmonella can cause significant economic and public health problems. Its prevention is accomplished by the use of antibiotics, but appearance of resistant strains has raised the need to search for alternatives. Recently, Salmonella-specific bacteriophages were identified and suggested as a therapy product in poultry. The large-scale production of this product requires the development of recovery/purification strategies to maximize product quality and minimize production costs. Aqueous two-phase systems (ATPS) have been used for different bioproducts, but few reports exist for the recovery of phages with this technique. This work analyzed the use of PEG-Salt and Ionic Liquid-Salt systems to characterize the partition of three phages samples: (1) Phage crude lysate containing phages, cell debris and bacterial cells (2) Centrifuged lysate containing phages, cell debris but reduced bacteria due to a centrifugation process (3) Filtered Lysate Phage containing phages and cell debris, without bacterial cells. Phage infectivity was measured in each of the ATPS components to determine the optimal system through recovery, purification fold and stability. Results indicate that phages partition to PEG 400 or ionic liquid phases, but in a PEG8000-Salt system, partition is favored to the salt-rich phase (55 and 3000-fold for phage crude lysate and filtered plate lysate, respectively) with a high recovery (60 and 90% for the same samples). Moreover, this salt phase provided the largest purification fold (up to 127-fold) and no significant reduction in infectivity. These findings serve as a platform for potential scale-up of bioprocesses for the recovery/purification of phage therapy products.