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KMID : 0880220140520040324
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Journal of Microbiology
2014 Volume.52 No. 4 p.324 ~ p.332
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Optimization of Antifungal Lipopeptide Production from Bacillus sp. BH072 by Response Surface Methodology
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Xin Zhao
Ye Han
Xi-qian Tan
Jin Wang
Zhi-jiang Zhou
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Abstract
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Antifungal lipopeptide produced by Bacillus sp. BH072 was extracted from fermentation liquor and determined as iturin A by liquid chromatography-mass spectrometry (LC-MS). For industrial-scale production, the yield of iturin A was improved by optimizing medium components and fermentation conditions. A one-factor test was conducted; fermentation conditions were then optimized by response surface methodology (RSM) to obtain the following: temperature, 29.5°C; pH 6.45; inoculation quantity, 6.7%; loading volume, 100 ml (in 500 ml flasks); and rotary speed, 150 rpm. Under these conditions, the mass concentration of iturin A was increased from 45.30 mg/ml to 47.87 mg/ml. The following components of the medium were determined: carbon sources (glucose, fructose, sucrose, xylose, rhamnose, and soluble starch); nitrogen sources (peptone, soybean meal, NH4Cl, urea, and ammonium citrate); and metal ions (Zn2+, Fe3+, Mg2+, Mn2+, Ca2+, and K+). The effects of these components on iturin A production were observed in LB medium. We selected sucrose, soybean meal, and Mg2+ for RSM to optimize the conditions because of several advantages, including maximum iturin A production, high antifungal activity, and low cost. The optimum concentrations of these components were 0.98% sucrose, 0.94% soybean meal, and 0.93% Mg2+. After iturin A production was optimized by RSM, the mass concentration reached 52.21 mg/ml. The antifungal specific activity was enhanced from 350.11 AU/mg to 513.92 AU/mg, which was 46.8% higher than the previous result. The present study provides an important experimental basis for the industrial-scale production of iturin A and the agricultural applications of Bacillus sp. BH072.
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KEYWORD
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Bacillus, antifungal peptide, optimization
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