Efficient expression of the Aspergillus niger acidic protease PrA in Pichia pastoris

Abstract:

[Objective] To obtain a yeast strain efficiently producing the acidic protease PrA for applications in food processing, feed additives, and other related industries. [Methods] We constructed a recombinant strain of Pichia pastoris expressing PrA by fermentation in shake flasks and measured the enzymatic properties of the expressed PrA. Several strategies, such as signal peptide modification, gene dosage optimization, and co-expression with molecular chaperones, were employed to enhance the production of PrA. Additionally, high-density fermentation was employed to further improve the expression level. [Results] The expressed enzyme PrA showcased the specific activity of 3 974.00 U/mg, with the optimum performance at pH 3.0 and 45 ℃. The production of PrA by the parental strain was 738.03 U/mL. The modification of the MF4I signal peptide increased the production of PrA to 1 206.52 U/mL. Moreover, an increase in the copy number of prA further increased the PrA production to 2 406.47 U/mL. Additionally, co-expression with single or combined molecular chaperones increased the PrA production to 4 091.27 U/mL. After undergoing high-density fermentation, the enzyme activity reached 43 088.00 U/mL within 168 h, representing a 58.4-fold increase compared with the initial production. [Conclusion] High-level expression of PrA was achieved in P. pastoris, which laid a foundation for the future industrial applications. The results provide valuable insights into the research and development of PrA for applications in food processing and feed additives.