Abstract: An apparatus for isolating a microorganism from a liquid, the apparatus comprising: a first endcap engageable with an inlet end of a hollow fibre filter, the first endcap including a first passage having an inlet engageable with a liquid input conduit; and an outlet into the filter; and a second endcap engageable with an outlet end of the hollow fibre filter, the second endcap including a second passage having an outlet engageable with a liquid return conduit, and an inlet from the filter; the first passage and the second passage being independently sized such that in conjunction with a flow restriction means which restricts a flow of the liquid through the second passage, a predetermined exit liquid flow rate from at least one permeate outlet of the filter is achieved; the microorganism is captured within the hollow fibre filter; and the maximum working pressure of the hollow fibre filter is not exceeded.