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KMID : 0364820120480040298
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Korean Journal of Microbiology
2012 Volume.48 No. 4 p.298 ~ p.304
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Production and Characterization of Thermostable Protease from Bacillus licheniformis Isolated from Korean Traditional Soybean Paste
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Bae Young-Eun
Yoon Ki-Hong
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Abstract
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Among 63 Bacillus strains grown at 60℃ from sixteen samples of homemade Korean soybean paste, one strain was
selected for producing the thermostable protease. The isolate has been identified as Bacillus licheniformis on the
basis of its 16S rDNA sequence, morphology and biochemical properties. Culture filtrate of the isolate showed
maximal protease activity at the reaction condition of 60?65℃ and pH 11. The culture filtrate retained more than
87% of initial protease activity after incubation for 30 min at 60℃ without substrate. In order to develop the medium
composition, effects of ingredients including nitrogen sources, carbon sources, metal ions and phosphate were
examined for protease production of the isolate. Lactose and soytone peptone were the most effective carbon and
nitrogen source for the enzyme production. After the late logarithmic growth phase the isolate began to produce the
protease, and the maximum protease productivity was reached to 550 unit/ml in the optimized medium consisting of
lactose (3%), soytone peptone (1.5%), MgSO4 (0.1%), K2HPO4 (0.03%), and KH2PO4 (0.03%) at 28 h of incubation.
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KEYWORD
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Bacillus licheniformis, properties, protease productivity, soybean paste
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