Production of hepatitis B surface antigen (preS2 + S) by high-cell density cultivations of a recombinant yeast.

A high-cell density bioprocess has been developed for the production of hepatitis B surface protein (preS2 + S) by recombinant yeast. This fed-batch process utilizes a growth medium containing yeast extract, soy peptone and glucose which was fed at a constant rate to maintain cells in a respiratory state. Cell densities of up to 60 g l-1 dry weight were achieved, which represented a 6-fold increase over those from batch bioprocesses. This increase in cell mass was attained without compromising specific activity; therefore, volumetric productivities of six times those of batch bioprocesses were achieved.