Abstract:
Ranpirnase, a multi-functional protein drug, was first isolated from the oocytes and early embryos of the Northern Leopard Frog, and belonged to the ribonuclease A (RNase A) superfamily. Ranpirnase not only inhibits protein biosynthetic pathway, but also independently induces tumor cell apoptosis. It also has antiviral activity. In this study, in order to improve the expression level of ranpirnase in
E. coli, a Plackett-Burman (PB) experimental design was applied to examine the effect of various factors on ranpirnase expression in recombinant
E. coli. The recombinant
E. coli fermentation medium and inducing conditions were also optimized. On the basis of these results, the ranpirnase expression in recombinant
E. coli was carried out in a 7 L fermentor with the combined exponential and pH-Stat feeding strategy. With the optimized fermentation medium, the protein expression at the flask level increased from 9% to 36%, and the OD
600 value increased from 4.80 to 5.47. The expression level of ranpirnase at the 7 L fermentor level reached 55%, and the OD
600 value was increased to 35 after the optimization. The use of the optimized medium for high-density fermentation of ranpirnase leads to a lowered production cost, facilitating its commercialization.