This Isolation of bacterial phage WORKS Optimization Procedure is intended to isolate phage from cell culture media. This procedure is intended for recovery procedures which could be characterized as for lighter cultures that are not totally lysed and smaller phage sizes (20 - 80 nm). This optimization procedure uses a microfiltration (MF) membrane that retains the cells and cell debris and allows the bacterial phage to pass freely through the membrane. The passage characteristics of bacterial phages change with different buffers, temperatures, concentrations, and membranes. By examining the passage characteristics of the different MF membranes available in the appropriate process conditions, a well defined and executed process development study can identify the most efficient membrane and process conditions to achieve the required performance.