High performance affinity chromatography of Bacillus neutral proteases.

Bacillus neutral proteases were purified using bacitracin-silica as an affinity medium. Several chromatographic procedures were investigated, including high speed runs on columns with 40- to 60-microns silica particles. The high speed procedure enabled the purification of 4.9 mg of B. subtilis neutral protease directly from 165-ml culture supernatant within 1.5 h. The neutral proteases of B. polymyxa and B. stearothermophilus were also purified. The latter enzyme was further concentrated by a second affinity chromatography step, using Sepharose with glycyl-D-phenylalanine as a ligand. During the purification procedures isopropanol was used to prevent autodigestion of the enzymes.