An objective gas to be measured is introduced into first and second chambers which are connected via a diffusion resistive passage. The media includes a disk having cones extending perpendicularly from the surface thereof. The valve head preferably tapers radially inward with respect to the center axis in an upstream direction and from a peripheral outer edge of the head. Optionally, a pump introduces a carbon source such as molasses to the bioreactor to initiate and sustain microbiological metabolic processes. In addition, therapeutic treatment regimens are provided to promote transplant tolerance in a patient following the administration of B Lymphocyte Stimulatorantagonists.