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The Scientific World Journal
Volume 2012, Article ID 564932, 11 pages
Research Article

Optimization of Acid Protease Production by Aspergillus niger I1 on Shrimp Peptone Using Statistical Experimental Design

1Laboratoire de Génie Enzymatique et de Microbiologie, Ecole Nationale d’Ingénieurs de Sfax, Université de Sfax, BP 1173-3038, Sfax, Tunisia
2Faculté des Sciences de Sfax, Université de Sfax, BP 1171-3000, Sfax, Tunisia
3Laboratoire de Génie Enzymatique des Lipases, Ecole Nationale d’Ingénieurs de Sfax, Université de Sfax, BP 1173-3038, Sfax, Tunisia

Received 24 October 2011; Accepted 5 January 2012

Academic Editors: W. Hunziker and Y. Ueta

Copyright © 2012 Rayda Siala et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Medium composition and culture conditions for the acid protease production by Aspergillus niger I1 were optimized by response surface methodology (RSM). A significant influence of temperature, KH2PO4, and initial pH on the protease production was evaluated by Plackett-Burman design (PBD). These factors were further optimized using Box-Behnken design and RSM. Under the proposed optimized conditions, the experimental protease production (183.13 U mL1) closely matched the yield predicted by the statistical model (172.57 U mL1) with 𝑅2=0.914. Compared with the initial M1 medium on which protease production was 43.13 U mL1, a successful and significant improvement by 4.25 folds was achieved in the optimized medium containing (g/L): hulled grain of wheat (HGW) 5.0; KH2PO4 1.0; NaCl 0.3; MgSO4(7H2O) 0.5; CaCl2 (7H2O) 0.4; ZnSO4 0.1; Na2HPO4 1.6; shrimp peptone (SP) 1.0. The pH was adjusted at 5 and the temperature at 30C. More interestingly, the optimization was accomplished using two cheap and local fermentation substrates, HGW and SP, which may result in a significant reduction in the cost of medium constituents.