Two‐compartment processing as a tool to boost recombinant protein production

Pichia pastoris is used extensively as a production platform for many recombinant proteins. The dissolved oxygen (DO) is one of the most important factors influencing protein production. The influence of the DO on productivity has not been studied independent from the feed rate. In this work, various DO levels were investigated independent from the feed rate. The model system was recombinant P. pastoris under the control of methanol‐induced alcohol oxidase promoter, which expressed HRP as the target protein. No significant effect was observed in terms of titer and specific productivity, which is a confirmation of the fact that the DO in a one‐compartment system cannot boost productivity for the model system under study. Hence, a two‐compartment system (a single reactor coupled with a plug flow reactor) was designed and implemented in order to apply oxygen‐related stress in the plug flow reactor and allow the cells to be recovered in the main reactor. Doing so, more than two‐fold increase in the titer and productivity and three‐fold increase in protein‐specific activity were achieved. Hence, partial application of oxygen‐related stress in the two‐compartment system was proposed as a process technology to enhance protein production.