1991 Volume 17 Issue 3 Pages 680-686
Saccharomyces cerevisiae harbouring a recombinant plasmid pNW052 was cultured in a shake flask and a jar fermentor. In the recombinant plasmid, the mouse amylase gene was fused to S. cerevisiae PGK (phosphoglycerate kinase) promoter. In shake flask cultivations we found that ammonium sulphate inhibited the expression of mouse amylase from PGK promoter. By replacing ammonium sulphate with yeast extract, gene expression was enhanced and 10 kg/m3 yeast extract gave sufficient gene expression and cell growth. In addition to nitrogen source, we investigated the effect of glucose concentration on mouse amylase production from PGK promoter using an on-line glucose analyzer in a jar fermentor culture. When glucose concentration was controlled at 10 kg/m3, gene expression was repressed. On the other hand, when glucose was controlled at 0.15 kg/m3, mouse amylase was produced and secreted into the medium very efficiently. This amount of the enzyme was almost 10 -fold that obtained at 10 kg/m3 glucose. By the combination of an on-line glucose monitoring and control system and yeast PGK promoter, effective production of gene product could be achieved.
