A novel purification procedure for recombinant human serum albumin expressed in Pichia pastoris

Plasma-derived human serum albumin (pHSA) has important applications in many clinical indications, including blood loss, serious burn, or hemorrhagic shock. The limited supply and potential infectious pathogen contamination of pHSA have stimulated the development of recombinant human serum albumin (rHSA). However, rHSA often entraps endogenous or exogenous impurities, including color pigments and polysaccharides. Therefore, the purification of rHSA to high purity remains the bottleneck in large-scale production of rHSA. Herein we report a novel two-step purification protocol for rHSA generated from Pichia pastoris. In the first step, rHSA was partially unfolded to expose impurities entrapped into rHSA and was then removed. In the second step, rHSA was crystallized to further remove impurities. Through this procedure, the pigment content (A₃₅₀/A₂₈₀) and polysaccharides content of rHSA were reduced to 0.0141 and 0.253 μg/mg, respectively, which were comparable to pHSA. In addition, the secondary structure and bioactivity of purified rHSA are preserved. The purification procedure developed in this study is a simple, short and low cost method to produce active rHSA, or rHSA-fusion proteins, to high purity, and also suitable for the purification of other disulfide-rich proteins.