Single-step purification of recombinant Bm86 protein produced in Pichia pastoris by salting-out and by acid precipitation of contaminants

Two single-step purification methods were used to isolate the recombinant protein, rBm86, produced in Pichia pastoris. Salting-out results in a compromise between final purity and recovery of rBm86. At 15, 25 and 35% of ammonium sulphate saturation (pH 7), rBm86 concentration in the supernatant phase was proportional to the initial amount of protein. Acid precipitation of contaminants resulted in 98% purity and 98% recovery of rBm86. High aggregation of rBm86, forming particles of 28 nm, changed the isoelectric point of monomers (5.5), considering only the aminoacid sequence, to 4.5 for particles.