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| Optimization of solid state fermentation conditions for xylanase production using response surface methodology and the enzymatic properties |
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Abstract The production of xylanase (XylA) by a newly isolated Aspergillus niger JL15 strain in solid-state fermentation (SSF) on orange peel was optimized by response surface methodology (RSM). Results revealed that four factors of concentrations of added glycerin and ammonium sulfate, moisture content, fermentation time had significant effect on the XylA production (P<0.05). The maximum xylanase activity (917.7 U/g dry fermentation product) obtained at 4.2% glycerin, 3.1% (NH4)2SO4 by employing orange peel as the solid substrate, 61% moisture content and 73.4-h fermentation, which was close to the predicted one (922.9 U/g), and was 3.2 times higher than that of the basic medium (218.5 U/g). The optimum temperature and pH for XylA activity were 55°C and pH5.0, respectively. XylA exhibited Km and Vmax values of 9.24 mg/ml and 54.05 μmol/min/ml, respectively. HPLC analysis showed that XylA liberated mainly xylotriose from birchwood xylan and wheat bran, which suggested the XylA might be an endo-acting xylanase.
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Received: 19 January 2009
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