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Fermentation studies on recombinant yeast
Abstract
Recombinant Pichia pastoris fermentations consist of a batch growth phase on glycerol and a protein production phase on methanol. The overall fermentation process can be improved by optimizing the two phases separately. Using glycerol concentrations of up to 12%, a dry cell mass of 90 g L$\sp{-1}$ was achieved during growth at a constant pH of 5.00. When the pH was not externally controlled, growth stopped at pH 2.2 and glycerol concentration above 2% remained unutilized. There was no difference between the growth characteristics of a Mut$\sp+$ strain and a Mut$\sp-$ strain on glycerol. Heterologous protein expression under the regulation of the AOXI promoter was partially repressed by higher glycerol feed-rates and by ethanol accumulation in the medium. With the Mut$\sp-$ strain, a constant glycerol feed-rate of 1 g L$\sp{-1}$ h$\sp{-1}$ resulted in the highest specific yield of the recombinant protein, $\beta$-galactosidase. Higher glycerol feed-rates gave increased cell mass and ethanol, resulting in lower specific yields of the recombinant protein. The fermentation process with the Mut$\sp-$ strain used around 30-fold less methanol than with the fermentation process using the Mut$\sp+$ strain. Protein yields between the two processes were comparable.
Subject Area
Genetics|Microbiology|Chemical engineering|Molecular biology
Recommended Citation
Chiruvolu, Vijaykumar R, "Fermentation studies on recombinant yeast" (1996). ETD collection for University of Nebraska-Lincoln. AAI9628225.
https://digitalcommons.unl.edu/dissertations/AAI9628225