Background

Fermentation of methylotrophic yeast Pichia pastoris is finding increasing use as a host for the expression of a wide verity of recombinant proteins at the bench and pilot scales. There are a number of excellent reviews describing the general features of this yeast expression and fermentation system

Alternative yeast originally developed for the single cell protein (SCP) production, Pichia pastoris become increasingly attractive organism for this purpose. It has been commercially developed with an ease in genetic manipulation as an efficient host for expression of many foreign protein (Sahasrabudhe, 1998, Waterham, 1997). Pichia pastoris is an ideal host, because: (i) it is a simple microbe that is capable of growth to high cell densities on inexpensive, defined media using well-developed fermentation protocols; (ii) expression of foreign proteins in Pichia pastoris is driven by the very strong and tightly regulated AOX1 promoter that has been exploited by a number of vectors with reasonable transformation efficiencies; (iii) as simple eukaryotes, yeasts are capable of many of the same posttranslational modification to protein as higher animals; and (iv) yeasts are capable of secreting high level of many proteins, simplifying drown stream purification