Recombinant protein production in Pichia pastoris under glyceraldehyde-3-phosphate dehydrogenase promoter: From carbon source metabolism to bioreactor operation parameters

• We review the current state of art on r-protein production by Pichia pastoris under PGAP.
• Bioprocess parameters and strategies are analysed for r-protein production.
• Carbon source and oxygen modulate r-protein production under PGAP.
• Requirement for the studies on molecular basis of PGAP regulation is discussed.
• New strategies for the enhanced production of r-proteins under PGAP are discussed.

The yeast Pichia (Komagataella) pastoris has become a potential host system for recombinant protein (r-protein) production. Several strong inducible and constitutive promoters have been identified in P. pastoris which make the host ideal in r-protein expressions. The constitutive promoter of the glyceraldehyde-3-phosphate dehydrogenase gene, PGAP, is promising as its use offers the advantage of associating product quantity to growth which can be optimized by a well-designed feeding strategy so long as the product itself is not toxic to the host. In this article, carbon source metabolism and the central carbon pathways of P. pastoris are reviewed. After comparing PGAP with the available promoters of P. pastoris, the bioreactor operation parameters and bioreactor operation strategies are analyzed for r-protein production under PGAP by focusing on response of the cells, final product concentration, yield, and productivity. The overview of the subject reveals the requirement for in-depth information on the overall regulation of P. pastoris metabolism that can enable fine-tuning bioreactor operation parameters in relation with the physiology of the microorganism in order to develop new strategies for the enhanced r-protein production.