Decrease of proteolytic degradation of recombinant hirudin produced by Pichia pastoris by controlling the specific growth rate

The effects of the specific growth rate and methanol concentration on the degradation of hirudin produced by recombinant Pichia pastoris were investigated. When a methanol-limited state and the specific growth rate of 0.02 h^–1 were maintained during the fermentation, a minimum degradation of hirudin and a maximum specific hirudin production rate were achieved. By this strategy, the production of intact recombinant hirudin Hir65 reached 0.7 g l^–1 in fed-batch fermentation. Its proportion was 35% to all forms of hirudin.