Enhancing the efficiency of recombinant hepatitis B surface antigen production in Pichia pastoris by employing continuous fermentation

Abstract

The recombinant hepatitis B surface antigen (rHBsAg) is a protein-based vaccine which is mainly produced by Pichia pastoris (P. pastoris) in a high-cell-density fed-batch fermentation for large-scale production purposes. In this study, we compared the efficiency and productivity of a chemostat fermentation of P. pastoris for rHBsAg production with the conventional fed-batch fermentation process. For this purpose, we established chemostat fermentation of P. pastoris for rHBsAg production in bench-scale for two weeks. The specific and volumetric productivity for chemostat fermentation were 0.00468 mg HBsAg/g cell/h and 1.699 mg HBsAg/L/h, respectively. These parameters for fed-batch fermentation were 0.00456 mg HBsAg/g cell/h and 1.38 mg HBsAg/L/h, and by considering the downtime for harvesting and initiating the next run, these values dropped to 0.00375 mg HBsAg/g cell/h and 1.13 mg HBsAg/L/h, respectively. According to the PCR analysis, no genetic mutation and contamination were detected after approximately three weeks of fermentation process- including batch, fed-batch and chemostat fermentation. These results indicate large-scale production of rHBsAg in recombinant P. pastoris, using the chemostat operation mode is more cost-effective and time-sparing than the conventional fed-batch production system. Besides, common challenges such as contamination and mutation were absent in the continuous production of rHBsAg in P. pastoris.