Original Paper

Bioprocess and Biosystems Engineering

, Volume 26, Issue 3, pp 159-163

Anaerobic and aerobic continuous cultures of Saccharomyces cerevisiae: comparison of plasmid stability and EXG1 gene expression

  • T. A. Lú-ChauAffiliated withDepartment of Chemical Engineering, Institute of Technology, University of Santiago de Compostela Email author 
  • , A. GuillánAffiliated withDepartment of Chemical Engineering, Institute of Technology, University of Santiago de Compostela
  • , M. J. NúñezAffiliated withDepartment of Chemical Engineering, Institute of Technology, University of Santiago de Compostela
  • , E. RocaAffiliated withDepartment of Chemical Engineering, Institute of Technology, University of Santiago de Compostela
  • , J. M. LemaAffiliated withDepartment of Chemical Engineering, Institute of Technology, University of Santiago de Compostela

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Abstract

Two bioreactor continuous cultures, at anaerobic and aerobic conditions, were carried out using a recombinant Saccharomyces cerevisiae strain that over-expresses the homologous gene EXG1. This recombinant system was used to study the effect of dissolved oxygen concentration on plasmid stability and gene over-expression. Bioreactor cultures were operated at two dilution rates (0.14 and 0.03 h−1) to investigate the effect of other process parameters on EXG1 expression. Both cultures suffered severe plasmid instability during the first 16 generations. Segregational plasmid loss rate for the aerobic culture was two-fold that of the anaerobic operation. In spite of this fact, exo-β-glucanase activity at aerobic conditions was 12-fold that of the anaerobic culture. This maximal activity (30 U ml−1) was attained at the lowest dilution rate when biomass reached its greatest value and glucose concentration was zero.

Keywords

Bioreactor continuous operation Dissolved oxygen EXG1 Plasmid stability Recombinant Saccharomyces cerevisiae