Fermentation of recombinant yeast producing hepatitis B surface antigen

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Abstract
Fermentations were performed to determine parameters affecting the expression of hepatitis B surface antigen (HBsAg) in the yeastSaccharomyces cerevisiae containing the HBsAg gene. These studies emphasized inereasing both the relative abundance (HBsAg: cell mass) and total production of HBsAg. Specific activity was increased 70-fold when cells were grown in shake flasks containing nonselective rather than selective medium. The addition of adenine, ammonium sulfate or glucose to the complex medium reduced the production of antigen. Results similar to those achieved in shake flasks were obtained when the growth was performed in fermenters. A nutrient addition system was employed to increase the production of cells and HBsAg. The addition of glucose to the culture medium increased cell mass 6-fold but decreased the production of antigen. This imbalance was corrected by supplementing the glucose with complex nutrients.