Effect of media composition on growth, plasmid stability and ovine interferon-tau production in Saccharomyces cerevisiae

Recombinant protein production is often influenced by the stability of plasmid carrying the cloned gene and the final biomass yield. Ovine (sheep) interferon-tau (oIFN tau) has been expressed in Saccharomyces cerevisiae under the regulation of a hybrid alcohol dehydrogenase 2/glyceraldehyde-3-phosphate dehydrogenase promoter. The influence of media composition on growth rate, biomass yield, plasmid stability and oIFN tau were studied. In a selective medium, with leucine and uracil selection, the plasmid stability was good but the yeast failed to grow to high cell densities. In 60-l fermentations, oIFN tau yields of 49 mg/l were achieved for complex media and about 3.4 mg/l for casamino acids with uracil selection based on bioassay. A fraction of the protein was insoluble and was solubilized by 6 M guanidine hydrochloride.