African Journal of Biotechnology Vol. 6 (22), pp. 2559-2564, 19 November 2007   

ISSN 1684–5315 © 2007 Academic Journals        

Full Length Research Paper

Enhancement of alkaline protease production by Bacillus clausii using Taguchi experimental design

Seyedeh Faranak Ghaemi Oskouie¹, Fatemeh Tabandeh²*, Bagher Yakhchali² and Fereshteh Eftekhar¹

¹Biology Department, Faculty of Science, Shahid Beheshti University, Chamran Highway, Evin, 19839, Tehran, Iran.

²Industrial and Environmental Biotechnology Department, National Institute of Genetic Engineering and Biotechnology (NIGEB), Pajhoohesh Blvd., Tehran-Karaj Highway, 1417863171, Tehran, Iran.

*Corresponding author. E-mail: taban_f@nicgeb.ac.ir, Tel.: +98 21 44580359; Fax: +98 21 44580399.

Accepted 27 September, 2007

The effect of culture conditions on protease production and bacterial growth of Bacillus clausii was investigated using Taguchi design of experiment. Five factors viz., carbon source, organic and inorganic nitrogen sources, agitation and metal ion, each at four levels were selected and an orthogonal array layout of L16 (4⁵) were performed. The proposed medium for alkaline protease production consisted of (g/l): sucrose, 10; yeast extract, 10; KNO₃, 5; trace element without Mn²⁺. Under these optimal conditions, 4 fold enhancement in protease production (from 250 to 1000 U/ml) was obtained. At the optimum culture for bacterial growth, which contained (g/l): starch, 10; yeast extract, 10; ammonium ions, 5; trace element without Zn²⁺, 1.88 fold increase in growth production (from OD_{600 nm} of about 8.5 in basal medium to OD_{600 nm} of 16 in optimized medium) were observed. The inorganic nitrogen source was the most significant factor on protease production with 57.75% contribution. The organic nitrogen and carbon sources by 35.28 and 34.93% contributions were prominent factors in bacterial growth.

Key words: Alkaline protease, Bacillus clausii, medium optimization, taguchi method.