a bioreactor includes a plastic enclosure for containing a biological medium , the enclosure being integrally formed to have one or more elongate port extensions projecting outwardly from the enclosure and communicating from the exterior to the interior of the enclosure . a biomass impendence monitor probe is provided for use in conjunction with the bioreactor . the probe is pushed into one or more of the elongate ports in order to have an electrode arrangement positioned internally of the container . the probe has an elongate housing having an outer surface extending along and contiguous with the elongate inner surface of the port extension . the housing extends from the electrode end of the probe to a remote end . the housing is provided with an electrical connector connected to the electrode arrangement .