Full Length Research Paper

Optimization of medium composition for thermostable protease production by Bacillus sp. HS08 with a statistical method

Huang Guangrong¹, Dai Dehui², Hu Weilian² and Jiang Jiaxin¹*

¹College of Life Science, China Jiliang University, Hangzhou, Zhejiang 310018, China.

²School of Biological and Chemical Engineering, Zhejiang University of Science and Technology, Hangzhou, Zhejiang 310012, China.

*Corresponding author. E-mail: cnjxjiang@126.com. Tel (fax): 0086 571 86875628.

Accepted 21 February, 2008

Optimization of the fermentation medium for maximization of thermostable neutral protease production by Bacillus sp. HS08 was carried out. After screening various elements, carbon and nitrogen sources, response surface methodology (RSM) was applied to optimize the medium constituents. A 2⁴ full-factorial central composite design (CCD) was chosen to explain the combined effects of the four medium constituents; corn starch, soybean meal, glucose and yeast extract. The optimized values obtained by the statistical analysis showed that corn starch at 19.8 g/l, soybean meal at 9.7 g/l, glucose at 3.6 g/l and yeast extract at 3.9 g/l gived maximum protease activity of 6804 U/ml.

Key words: Medium optimization, response surface method, thermostable protease, Bacillus sp.