PRODUCTION OF PROTEINASE-A BY SACCHAROMYCES-CEREVISIAE IN A CELL-RECYCLING FERMENTATION SYSTEM - EXPERIMENTS AND COMPUTER-SIMULATIONS

Overproduction of proteinase A by recombinant Saccharomyces cerevisiae was investigated by cultivations in a cell-recycling bioreactor. Memb rane filtration was used to separate cells from the broth. Recycling r atios and dilution rates were varied and the effect on enzyme producti on was studied both experimentally and by computer simulations. Experi ments and simulations showed that cell mass and product concentration were enhanced by high ratios of recycling. Additional simulations show ed that the proteinase A concentration decreased drastically at high d ilution rates and the optimal volumetric productivities were at high d ilution rates just below washout and at high ratios of recycling. Cell -recycling fermentation gave much higher volumetric productivities and stable product concentrations in contrast to simple continuous fermen tation.