The proposed research is aimed at maximizing the performance of recombinant cell fermentation processes through optimizing environmental conditions. This goal is to be achieved by investigating two model systems: - alpha-amylase production from recombinant E. coli. - invertase production from recombinant Saccharomyces cerevisiae. Environmental conditions strongly affect the transription efficiency of the genes under the control of regulated promoters, and consequently the expression level of the target proteins. Growth temperature and medium osmolarity affect the expression and transport of alpha-amylase. Invertase synthesis is influenced by the glucose content of a fermentation medium, which influences the SUC2 promoter transcription efficiency and hence the invertase expression level. A slowly metabolized inducer like sucrose monopalmitate may be more effective in increasing invertase production. Model equations describing responses of the recombinant cell to various culture conditions will be formulated and incorporated into fed-batch fermentation processes in an effort to search for an optimum operation strategy. The mathematical modeling and optimization theory developed for nonrecombinant cells will be readily extended to recombinant cell cultures after taking into consideration unique features of recombinant cells such as plasmid stability and promoter induction. The PI is considered to be well qualified to carry out the proposed research and I recommend funding of this proposal.