Acid protease recovery from a solid-state fermentation system

Investigations have been carried out on an acid protease produced by Mucor bacilliformis under solid-state fermentation conditions as a model of recovery and purification of a protein from a solid culture medium. The leaching efficiency of sodium chloride solutions to recover the enzyme from the fermented mass was higher than that of non-ionic detergents (Triton X-100 or Tween 80) or distilled water. Concentration and coarse fractionation of the crude extract could be achieved with a high yield of protease by precipitation with ethanol or acetone and by ultrafiltration and diafiltration in the presence of NaCl. Diafiltration was selected for the prechromatographic treatment of the crude extract as it enhances the maximum fraction of enzyme bound to an anion-exchanger up to 0.9. An overall purification factor of 15.5 was reached, with a total enzyme recovery of 46%, with the purification procedure developed by using this methodology. The final product obtained was a highly purified food-grade protease preparation. (C) 1998 Elsevier Science B.V. All rights reserved.