A method includes directing fluid flow from a bioreactor to an external path of a re-circulation loop, separating cells from the medium and returning the cells to the bioreactor thereby leaving spent medium, depleting the spent medium of biological waste products, replenishing the spent medium with beneficial growth factors to thereby provide replenished medium, and directing the replenished medium back to the bioreactor to thereby complete the re-circulation loop such that recycling of the medium occurs. The replenishing of the spent medium with beneficial growth factors may occur within a medium collection reservoir. The method may further include monitoring the spent medium within the medium collection reservoir including temperature of the spent medium within the medium collection reservoir and pH of the spent medium within the medium collection reservoir.