Yeast expression platform

In general a microorganism used as an expression platform has to meet several criteria: it should be able grow rapidly in large containers, produce proteins in an efficient way (i.e. with minimal resource input), be safe and, in case of pharmaceuticals, it should produce and modify the products to be as ready for human consumption as possible.

They offer relatively easy genetic manipulation and rapid growth to high cell densities on inexpensive media.

Due to this, yeast can produce complex proteins that are identical or very similar to native products from plants or mammals.

However since then a variety of yeast expression platforms have been studied and are widely used for various applications based on their different characteristics and capabilities.

For instance some of them grow on a wide range of carbon sources and are not restricted to glucose, as it is the case with baker’s yeast.

A computational method, IPRO, recently predicted mutations that experimentally switched the cofactor specificity of Candida boidinii xylose reductase from NADPH to NADH.

As an expression platform it has successfully been applied to the production of technical enzymes and of pharmaceuticals like insulin and hepatitis B vaccines.

The various yeast expression platforms differ in several characteristics, including their productivity and with respect to their capabilities to secrete, to process and to modify proteins in particular examples.

Most importantly, vectors contain a segment responsible for the production of the desired compound, called an expression cassette.

Fig. 1. Design and functionality of CoMed vector system. The CoMed basic vector contains all E. coli elements for propagation in the E. coli system and a MCS (multiple cloning ste) for integration of ARS, rDNA, selection marker and expression cassette modules. For this purpose, ARS fragments are flanked by Sac II and Bcu I restriction sites, rDNA regions by Bcu I and Eco 47III restriction sites, selection markers by Eco 47III and SalI restriction sites and promoter elements by Sal I and Apa I restriction sites.