Human chymotrypsinogen B production with Pichia pastoris by integrated development of fermentation and downstream processing. Part 1. fermentation

Based on an integrated approach of genetic engineering, fermentation proces s development, and downstream processing, a fermentative chymotrypsinogen B production process using recombinant Pichia pastoris is presented. Making use of the P. pastoris AOX1-promotor, the demand for methanol as the single carbon source as well as an inducer of protein secretion enforced the use of an optimized feeding strategy by help of on-line analysis and an advance d controller algorithm. By using an experimental system of six parallel spa rged column bioreactors, proteolytic product degradation could be minimized while also optimizing starting conditions for the following downstream pro cessing. This optimization of process conditions resulted in the production of authentic chymotrypsinogen at a final concentration level of 480 mg(.)L (-1) in the whole broth and a biomass concentration of 150 g(.)L(-1) cell d ry weight, thus comprising a space-time yield of 5.2 mg.L(-1.)h(-1). Altern atively to the high cell density fermentation approach, a continuous fermen tation process was developed to study the effects of reduced cell density t oward oxygen demand, cooling energy, and biomass separation. This developme nt led to a process with a highly increased spacetime yield of 25 mg(.)L(-1 ) h(-1) while reducing the cell dry weight concentration from 150 g(.)L(-1) in fed-batch to 65 g(.)L(-1) in continuous cultivation.