Skip to main content


You are viewing the new article page. Let us know what you think. Return to old version

Oral Presentation | Open | Published:

Enhanced protein expression through strain selection, gene disruption, improved vector design and co-expression of endogenous chaperones


The use of Saccharomyces cerevisiae as a host system has been limited by the perception of limited secretion capacity, unstable episomal vectors and aberrant glycosylation. Solutions to all of these limitations are now available.


An analysis of a series of haploid laboratory yeast strains revealed significant intra-strain variability and unstable plasmid segregation. By combining classic chemical mutagenesis and selection a family of highly efficient Saccharomyces cerevisiae strains has been developed for the commercial production of biopharmaceutical products. When combined with a stable [1], high copy number [2], episomal expression vector system and a strong constitutive promoter, secreted recombinant protein expression titres in excess of 4 g/L were achieved (see Figure 1). Specific genetic modifications to the host were also introduced to increase product yield and control post-translational modifications, such as proteolysis and glycosylation.

Figure 1

Enhancement of protein production through chemical mutagenesis and specific gene disruptions.

The expression vectors have been further enhanced to facilitate the stable co-expression of multiple proteins. When one of these proteins is a chaperone, the titre of co-expressed recombinant transferrin was increased 15-fold. The applicability of this system has been demonstrated with a wide range of heterologous proteins and is scalable from 10 mL shake flask to cGMP manufacture at high cell density fermentation (8,000 L) in a defined synthetic medium; designed to be integrated with cost-efficient downstream processing.


Significant intra-strain variability and unstable episomal plasmid systems have limited the usefulness of Saccharomyces cerevisiae as an industrial host for the production of biopharmaceuticals. However co-enhancement of the episomal vector system and the host strains is not only possible but has led to significant improvements in recombinant protein production.


  1. 1.

    Chinery SA, Hincliffe E: A novel class of vector for yeast transformation. Curr Genet. 1989, 16: 21-25. 10.1007/BF00411079.

  2. 2.

    Sleep D, Finnis C, Turner AJ, Evans LR: Yeast 2 mm plasmid copy number is elevated by a mutation in the nuclear gene UBC4 . Yeast. 2001, 18: 403-421. 10.1002/yea.679.

Download references

Author information

Correspondence to Darrell Sleep.

Rights and permissions

Reprints and Permissions

About this article


  • Strong Constitutive Promoter
  • Episomal Vector
  • Biopharmaceutical Product
  • High Cell Density Fermentation
  • Increase Product Yield