High-level secretion of human bikunin from recombinant Pichia pastoris.

Human bikunin is a glycoprotein that exhibits trypsin inhibitory activity against serine proteases, and is effective in clinic. However, limited productivity and high price of human bikunin retard its further application. In this study, a high-yield, low-cost process of recombinant human bikunin (rh-bikunin) production from Pichia pastoris was established. The trypsin inhibitory activity reached 6·2 × 10(3)  IU ml(-1) after 120 h induction of P. pastoris fermentation process, which was 20-fold higher than that of the previous yield. Furthermore, a simple and low-cost purification process, including ammonium sulphate precipitation, anion exchange adsorption of impurity and cation exchange chromatography, was developed with the results of 38·7% recovery and 96·6% purity of rh-bikunin. This work made a big step to improve bikunin further application in clinic. This study demonstrated the highest rh-bikunin production process towards its application as trypsin inhibitor in clinic. In this work, Pichia pastoris GS115 was used as a host for higher rh-bikunin production which was 20-fold higher than that of P. pastoris X-33. Then, a simple, low-cost purification procedure of rh-bikunin was developed. This potential high productivity and low cost of rh-bikunin process will benefit patients eventually.