The FISP® is sterilized in the vessel with the probe immersed in the fermentation broth or culture media. A peristaltic pump (or the vessel's own hydrostatic pressure) withdraws a sample through the tubular membrane and into the probe's stainless steel network of grooves. The sample flows through the network of grooves into a central channel where the cell-free sample can be directed to an on-line analyzer or fraction collector or sample container. Fluid flow rate is dependent on the viscosity of the media and will not exceed 2 ml/min.