Expression and Purification of Recombinant Human Growth Hormone in Pichia pastoris

In order to express the hGH in Pichia pastoris,total gene of human growth hormone was synthesized according to partial gene code of yeast (Pichia pastoris). The gene fragment was inserted into shuttle plasmid pPIC9K,then the recombinant plasmid ppIC9K-hGH was transformed into Pichia pastoris strains GS115 with PEG1000 and screening the multicopy clones by G418 in YPD plates. In the inducement of methanol,recombinant hGH was successfully expressed in Pichia pastoris. After optimizing the fermentation conditions,the yield of recombinant protein reached 1 537 mg/L in the supernatants,the purity of recombinant hGH can reach 97% after one step ultrafiltration and two step purification,and the 35% of the total protein can be obtained after optimizing the purication method. Mass spectrometry analyses showed the mass of the rhGH was close to the theoretic value. Amino acid sequencing of N-terminal indicated the rhGH was expressed successfully.