Optimization Studies on Extracellular Protease Production by Aspergillus niger and Aspergillus terreus Using Skim Milk Casein as Substrate

Aim: Proteases are proteolytic enzymes that have a wide range of applications in the industrial sectors. This study investigated the production and optimization of protease by protease-producing fungi, (Aspergillus niger and A. terreus) using skim milk casein as substrate.

Materials and Methods: Aspergillus terreus and A. niger obtained from the Department of Plant Science and Biotechnology, University of Jos, Nigeria were screened for extracellular protease on skim milk agar medium. Optimization studies across different parameters: temperatures (30-80oC), pH (3-10), substrate Concentration (0.25-2 %), and incubation period (6 days) using submerged fermentation were done for maximum protease activity.

Results: The maximum temperature of protease activity was 50oC (116.5 IU/ml) for Aspergillus niger and 40oC (121.86 IU/ml) for Aspergillus terreus. The Optimum pH for protease activity was pH 9 (106.85 IU/ml) for Aspergillus niger and pH 8 (107.90 IU/ml) for Aspergillus terreus. Optimum protease activity (29.36 IU/ml) at an incubation period of 48 hours was recorded for Aspergillus niger and 72 hours (182.2 IU/ml) for Aspergillus terreus. At 2% substrate concentration a maximum activity of 87.21 IU/ml and 76.5 IU/ml was recorded for Aspergillus niger and A. terreus, respectively.

Conclusion: The test fungi Aspergillus niger and Aspergillus terreus exhibited maximum hydrolytic potential for protease production which has a vast application in different industries.