Control of specific growth rate for the enhanced production of human interferon α2b in glycoengineered Pichia pastoris : process analytical technology guided approach

BACKGROUND Process variability in bioprocess systems involving genetically engineered strains is a common bottleneck and a real‐time insight of the on‐going process is crucial to achieve the desired product and its quality. In this study, a process analytical technology (PAT) platform was developed for the monitoring and control of specific growth rate during methanol induction phase ( μ met ) of glycoengineered Pichia pastoris fermentation for human interferon alpha 2b (huIFNα2b) production. RESULTS The PAT guided approach involves real‐time monitoring of capacitance (Δ C ) facilitating online estimation of specific growth rate ( μ est ), which serves as a process input during controller application. Fed‐batch experiments using pulsed‐feeding of methanol at different dosage (20 g and 30 g) did not significantly influence μ met . Exponential methanol feeding was achieved using a modified proportional, integral and derivative (PID) controller for different predefined specific growth rate set point ( μ sp ) values, namely 0.015, 0.03, 0.04 and 0.06 h −1 . Exponential feeding strategy during the induction phase resulted in two crucial outcomes: (i) controlled methanol feeding rate (regulated by the developed PID controller) balanced the methanol consumption rate ( q s, met ) of the P. pastoris ; (ii) significant improvement in huIFNα2b titer (1483 mg L −1 ) and specific productivity (>0.4 mg g −1 . h) was achieved by the robust control of μ met at optimal (0.04 h −1 ) value. The purified huIFNα2b was found to exhibit antiproliferative effect against human breast cancer cell lines. CONCLUSIONS Efficient control of μ met at a very low narrow range was achieved with a long‐term controller stability (>10 h) and the highest titer reported to date for huIFNα2b (at optimal μ met ) in the yeast expression platform. © 2019 Society of Chemical Industry