MODELING AND OPTIMIZATION OF CLONED INVERTASE EXPRESSION IN SACCHAROMYCES-CEREVISIAE

The aim of this study is to determine the medium feeding strategy to maximize the invertase productivity of recombinant Saccharomyces cerevisiae using a fed-batch mode of operation. The yeast contains the plasmid, pRB58, which contains the yeast SUC2 gene, coding for the enzyme invertase. The expression of this gene is repressed at high glucose levels. A goal-oriented model is developed to describe the kinetics of fed-batch fermentations. This simple model could quantitatively describe previous experimental results. A conjugate gradient algorithm is then used, in conjunction with this mathematical model, to compute the optimum feed rate for maximization of invertase productivity. The optimal feeding procedure results in an initial high cell growth phase followed by a high invertase production phase.