Studies on fermentation with recombinant yeast cells: plasmid stability and kinetics of biomass and protein production

Plasmid stability of the recombinant Saccharomyces cerevisiae YPB-G strain harbouring a YEp plasmid with alpha-amylase and glucoamylase genes as a fus ion has been investigated in shake flasks and in a bioreactor using various compositions of media containing glucose or starch as the main carbon sour ce. The medium composition affected both the growth characteristics and the stability of the plasmid. Superior plasmid stability was obtained in yeast minimal medium and in complex medium with glucose. Plasmid stability was s ubstantially increased at high growth rates. Additional data were collected in the same system to investigate the kinetic characteristics of biomass a nd protein production, and unstructured kinetic models were used to interpr et the results. At high initial glucose concentrations, where the biomass a nd protein production rates were similar, the kinetic models displayed good fits associated with high degrees of correlation. (C) 2000 Society of Chem ical Industry.