Production of the soluble human Fas ligand by Dictyostelium discoideum cultivated on a synthetic medium

Human Fas ligand (hFasL) is of considerable interest since it is a type II transmembrane glycoprotein that induces programmed cell death, or apoptosis. In this study Dictyostelium discoideum was used to produce a soluble form of the human Fas ligand. The recombinant cells were adapted to a modified synthetic FM medium, called SIH medium. Cells adapted to the SIH medium reached about 2 times higher cell densities and hFasL concentrations on this medium compared with cells growing on the standard complex medium HL-5C. Even higher values were achieved by a dissolved oxygen-controlled fed-batch cultivation in a conventional stirred bioreactor on SIH medium. Cell densities of up to 5.5×107 ml−1 and a maximum hFasL concentration of 148 μg l−1 were obtained. These results were further improved by means of continuous cultivation of D. discoideum in a bioreactor equipped with cell retention by microfiltration. At low space velocity very high cell densities of up to 2.4×108 ml−1 and hFasL concentrations of up to 205 μg l−1 were achieved.