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The Pichia Expression system is licensed to more than 120 companies in the biotechnology, pharmaceutical, animal health and food industries. A recent improvement, the PichiaGlycoSwitch" system, adds new genes to Pichia to create strains that glycosylate proteins the same as mammalian cells. These new strains produce proteins that may have increased applications for human therapies.
High yield + high productivity + chemically defined media + product processing similar to mammalian cells + stable production strains + durability = lower protein production costs
Pichia pastoris is an established industrial yeast that can use methanol as its sole carbon source to produce energy and cellular materials at ultra-high levels (1-5). The first enzyme in the methanol pathway, alcohol oxidase, can make up as much as 35 percent of the soluble protein of the cell (6).
Several genes in Pichia's methanol utilization pathway have been cloned (7-10). Heterologous expression using elements of these genes produces recombinant proteins at levels equivalent to alcohol oxidase when transformed yeast is grown on a methanol feedstock.
High Cell Densities
When Pichia is grown with the proprietary, high-cell-density fermentation technology, unprecedented levels of cell mass per liter of fermentation fluid are produced (4). The system has attained dry-cell-weight densities exceeding 120 gram/liter and continuous fermentation productivities of 10 to 12 grams of recombinant protein/liter/hour.
The growth medium that feeds Pichia is completely defined (4). It consists of a simple, inexpensive formulation. The carbon source is fed to the fermentor at a rate designed to achieve maximum cell density while maintaining optimal production of foreign protein. This process minimizes any toxic effects the foreign protein might have on the yeast.
As a eukaryotic system, the Pichia Expression system produces mammalian-like proteins. For example, the expression of Hepatitis B surface antigen (I-IBsAg) in Pichia leads to production of particles that are immunoreactive with anti-HBsAg antibodies (11). These particles are similar to Dane particles isolated from the sera of human carriers.
Generations of Stability
Expression of foreign genes is achieved by integration of foreign DNA into the chromosomal DNA of Pichia. The integrated DNA is stable for many generations; all cells can produce the protein (4). In contrast, plasmid-based systems require selective pressure on plasmids to maintain the foreign DNA. Cells that lose the plasmid cannot produce the desired foreign protein.
The Pichia Expression system requires no special handling. It was developed to withstand the adverse conditions of large scale, continuous fermentors. This feature makesPichia able to survive unexpected disruptions in the fermentation process.
High per-cell expression levels combined with high cell-density growth of Pichia translates into greater quantities of recombinant protein per fermentor volume. This reduces production costs by increasing the amount of product per fermentation run.
Protein purification is another cost-saving area. ThePichia Expression system can secrete protein into the medium, so the broth that enters purification contains a higher concentration of the desired protein. Pure protein is recovered with higher yield and lower cost (12).
Patents issued in the United States, Europe, Canada, Japan, Australia and other countries are available on request.
Mammalian-Like Glycosylation - PichiaGlycoSwitch®
In collaboration with Roland Contreras, Ph.D., and colleagues at Ghent University and the Flanders Institute for Biotechnology (VIB) in Belgium, RCT has developed a way to manipulate thePichia glycosylation system to produce uniform, small ASN-linked glycans on any glycoprotein of interest. These glycans have the same structure as processing intermediates of the mammalian N-glycosylation pathway. This improvement to RCT'sPichia platform is called Pichia GlycoSwitch®. If you are interested in evaluating the potential of thePichia GlycoSwitch® strains and vectors, please click here.
For Pichia kit purchases, technical and custom services:
Life Technologies (formerly Invitrogen Corp.)
Telephone: (800) 955-6288
Kurt R. Gehlsen, Ph.D., Vice President and Chief Scientific Officer
or Andrea Isner, assistant to Kurt Gehlsen