Production of foreign proteins in fed-batch fermentations of recombinant Saccharomyces cerevisiae

Abstract

The research was undertaken to characterize the expression behavior of recombinant S. cerwisiae systems and to optimize the production of cloned proteins in fed-batch fermentations. The product protdns of interest are lurudin and invertase. A fed-batch mode of operation provides more tight control over fermentation variables such as subst* rate concentration and hence improves the overall product yield compared with other types of operation. A fed-batch culture of the hirudin-producing recombinant yielded tiie final hirudin concentration 260mg/l and final diy cell weight llOg/1, which correspons to a 3.5-fold increase in cell den^ty and a 4.1-fbld enhancement in hirudin concentration compared with the batch term幻rotation. The expression of invertase in the recombinant yeast uith plasmid pRB58 was derepressed at glucose levels below 2幻/L The response of specific invertase activity to changes in the medium glucose concentration was found to be almost immediate. The dependence of glucose concmtration on cell growth and invertase expression was mathematically described by using a cybernetic concept A conjugate gradient algoriflim in conjunction with the model equations was used to confute the optimum glucose feed rate for maximization of invertase productivity. The optimal fee소ng procedure results in an initial hi없！ cell growtfi phase followed by a hig杜 cloned-gene expression phase.