Isolation of microbial strains producing acidic xylanase and characterization of the enzyme.

【Objective】 This study was aiming at screening acidic xylanase-producing microbes from natural environment for potential use in feed industry. 【Method】 Eighteen xylanase-producing strains were isolated from soil by enrichment culture techniques. Five strains were chosen to ferment in shaking flasks. Strain S8-3, which showed the highest xylanase production, was preliminarily identified by standard methods, and the property of the xylanase produced by the strain was studied. 【Result】 Strain S8-3 was identified as Aspergillus niger. The maximal enzymatic activity of xylanase in culture solution was 628.43 U·mL-1. The xylanase activity preformed optimally at 45℃ and pH 4.5. The xylanase was stable at pH ranging from 3.0 to 7.0 and retained more than 60 % of its original activity after incubation for 30 min at 70℃. 【Conclusion】 The xylanase produced by strain S8-3 in this study may have the potential in feed industry.