Research articles
ScienceAsia (): 118-124 |doi:
10.2306/scienceasia1513-1874...118
Optimization of silk degumming protease production from Bacillus subtilis C4 using Plackett-Burman design and response surface methodology
Nisa Romsomsaa, Patoomporn Chim-anagaea,*, Anuvat Jangchudb
ABSTRACT: Bacillus subtilis C4 was isolated from waste water of a Thai-silk dyeing factory, and identified as a potent strain for producing silk-degumming protease. To optimize the protease production of this bacterial strain, seven fermentation variables were screened using a Plackett-Burman design, and were then further optimized via response surface methodology based on a central composite design. Three significant variables, i.e., soy flour, skimmed milk, and shaker speed, were selected. The optimal values were 2.0% soy flour, 0.1% skimmed milk, and a shaker speed of 280 rpm. The experimental result (1537 units/ml) in a medium optimized for protease production was in good agreement with the predicted value of a quadratic model (1576 units/ml), thus confirming its validity. In addition, the adequacy of the model was supported by a coefficient of determination (R2) of 0.912. Protease production in the optimized medium (1537 units/ml) increased 2.2-fold over that of the non-optimized medium (729 units/ml) in the shaken flask culture. When the experiment was scaled up in a stirred tank reactor, 1891 units/ml protease activity was achieved at 27 h of cultivation, which was an overall 2.6-fold increase over the basal medium.
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| a |
Department of Microbiology, Faculty of Science, Kasetsart University, 50 Phahonyothin Rd, Chatuchak Bangkok 10900, Thailand |
| b |
Department of Product Development, Faculty of Agro-Industry, Kasetsart University, 50 Phahonyothin Rd, Chatuchak Bangkok 10900, Thailand |
* Corresponding author, E-mail: fscippc@ku.ac.th
Received 28 Jul 2009, Accepted 26 Mar 2010
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