Fig. 4 – SDS-PAGE (gradient gel 4–20%, silver stain).SDS-PAGE (gradient precast gel 4–20%, Bio-Rad, USA). Thegel was stained using the silver stain kit (Bio-Rad, USA).Kaleidoscope polypeptide standard (Bio-Rad, USA) wasused as molecular weight standard. At 150 V, 200 mA for90 min. (A) Molecular weight standard; (B) purified form ofcommercial nisin; (C) purified fraction of nisin producedin-house; (D) commercial nisin in crude.