Recombinant yeast technology at the cutting edge: robust tools for both designed catalysts and new biologicals

Health and safety concerns, enhanced quality criteria, and environmental sustainability, have prompted investigations into production using recombinant yeasts as a feasible alternative for isolation of proteins from natural animal or plant sources, as well as for processes utilising either mammalian cell cultures or bacterial systems. An overview of recent research papers and review articles provides readers with a comprehensive insight into the field of next-generation yeast expression systems. Major breakthroughs in recombinant yeast technology linked to Pichia pastoris are (i) the public availability of tools to generate proteins with tailored and highly homogenous N-glycan structures, similar to the forms assembled in humans, (ii) the recent accomplishment of the annotation of its genome sequence, and finally, (iii) the presence of the first few (non-glycosylated) therapeutic proteins in Pichia on the market. The P. pastoris expression platform is now well developed, as proven by multiple products used in human and veterinary medicine and in industry (e.g., enzymes for chemical synthesis and for the modification/synthesis of pharmaceuticals, drug target proteins used for structural analysis or for high throughput screening, proteins for diagnostics, proteinous biomaterials, vaccines, and therapeutic proteins). Nevertheless, the complexity of protein analysis (monitoring) continues to restrict process development for recombinant products. Drawing on combined expertise in molecular biology and process technology, the Institute of Biotechnology (IBT) at the Zurich University of Applied Science (ZHAW) and its international partners have developed solutions which (i) fully eliminate (or partially reduce) the use of methanol, which is undesirable in high-cell-density and high-productivity processes, (ii) match both strain construction and process design with the target protein characteristics to the benefit of the cells' physiological shape, and (iii) allow multi-gene expressions to be balanced to achieve custom tailored and reproducible protein quality at the level of (engineered) posttranslational modifications. In addition to enabling superior product quality specifications to be achieved with reduced development time, these innovations have helped the industries involved to minimise financial risks and the risk of failure, as well as create an opportunity for (new) drugs with improved functionality at low cost.