Controlled fed-batch fermentation of recombinant Saccharomyces cerevisiae to produce hepatitis B surface antigen

We have performed controlled fed‐batch fermentation experiments to compare the production level of hepatitis B surface antigen (HBsAg) by recombinant yeast Saccharomyces cerevisiae strains (YNN27/pYBH‐1, YNN27/ p2μ‐S11, YNN27/pDCB‐S2) containing plasmid vector with alcohol dehydrogenase (ADH1), acid phosphatase (PHO5), and glyceraldehyde‐3‐phosphate dehydrogenase (GPD) promoter, respectively. Yeast cell concentrations of 15‐35 g dry cell weight/L were obtained. By limiting phosphorous concentration, HBsAg expression level for the YNN27/p2μ‐S11 strain with inducible PHO5 promoter reached 0.2–0.3 mg/L. By controlling nutrient addition rate and dissolved oxygen concentration, HBsAg concentrations of 3‐10 mg/L were achieved in 60–70 h fermentation using the YNN27/pDCB‐S2 strain with the constitutive GPD promoter.