STUDIES ON THE PRODUCTION OF HUMAN PARATHYROID-HORMONE BY RECOMBINANTESCHERICHIA-COLI

Expression of human parathyroid hormone, hPTH(-1-84), by Escherichia c oli N4830:pEX-PPTH was studied in controlled bioreactors. The hPTH is expressed as a fusion protein under control of the bacteriophage lambd ap(R) promoter. In batch runs, low biomass concentrations but high spe cific hPTH productivities were obtained with complex TY (bactotryptone and yeast extract) medium whereas high biomass concentration and low specific productivities were found when fructose was used instead of b actotryptone (YF medium). The preinduction temperature was always 30-d egrees-C; the temperature shift to induce production of fusion protein was varied from 36 to 42-degrees-C. Formation of hPTH passed a pronou nced maximum as a function of induction temperature when using YF medi um. However, the optimum temperature shift was 38-degrees-C for both m edia used. For this temperature increase both media yielded about the same volumetric hPTH productivity (approx. 30 mg hPTH/l per hour). By applying a fed-batch strategy for the YF medium, the productivity of t he recombinant protein could be further increased more than fourfold. Compared to shake-flask experiments, the hPTH yield could be increased by a factor larger than 20.