Sorbitol as a non-repressing carbon source for fed-batch fermentation of recombinant Pichia pastoris

Glycerol/methanol and sorbitol/methanol mixed-feed fermentation strategies for the production of recombinant proteins by Pichia pastoris were compared in order to examine sorbitol's potential as a carbon source. Although P. p astoris does have a lower cell yield on sorbitol than on glycerol, the spec ific rate of product formation is higher (60 mu g protein g(-1) dry wt . h for sorbitol/methanol, vs 45 mu g protein g(-1) dry wt . h for glycerol/met hanol), resulting in comparable final recombinant expression levels. Import antly, the presence of residual sorbitol in the growth medium appears to be less repressive to the alcohol oxidase promoter in this organism, providin g a more forgiving means of operating mixed-feed fed-batch recombinant P. p astoris fermentations.