Modeling the growth and proteinase A production in continuous cultures of recombinant Saccharomyces cerevisiae

Abstract

Overexpression of the homologous protein proteinase A (PrA) in Saccharomyces cerevisiae has been achieved by inserting the PrA gene (PEP4) with its own promoter on a 2µ multicopy plasmid. With this system the specific PrA production rate was found to be described well by a linear function of the oxidative glucose metabolism, the reductive glucose metabolism, and the oxidative ethanol metabolism, with a significant lower yield resulting from the reductive glucose metabolism compared with the oxidative glucose metabolism. To describe the experimental data, a simple mathematical model has been set up. The model is based on an assumption of a limited respiratory capacity as suggested by Sonnleitner and Kä ppeli but extended to describe production of an extracellular protein. The model predicts correctly the critical dilution rate to be between 0.15 and 0.16 h −1 , the decrease in the biomass yield above the critical dilution rate, and the production of proteinase A at different dilution rates. Both the experimental data and model simulations suggest that the optimum operating conditions for protein production is just at the critical dilution rate.

Reverse engineering of protein secretion by uncoupling of cell cycle phases from growth

“…Secretion of heterologous proteins in yeasts is growth dependent (Carlsen et al, 1997; Giuseppin et al, 1993), reaching a plateau at high specific growth rates (Kobayashi et al, 2000; Maurer et al, 2006; Uchiyama and Shioya, 1999). The biological background of the correlation between protein secretion and growth is complex and by far not understood.…”

Discontinuities in continuous cultures studied with a recombinant Saccharomyces cerevisiae and two computer models

“…Yeast model, MC176 [11]. This model is based on a simple model of Sonnleitner and Ka Èppeli [12] assuming a limited respiratory capacity.…”