Abstract

The screening of thermophilic xylanase production strains was vital worth to enlarge their application range. A thermophilic xylanase production strain was screened from 11Aspergillus niger strains which were kept in lab. Its optimal pH value and temperature for its activity were 5.0 and 55°C, respectively. The range of pH stability was wide, and it was stable at pH range of 3.0 to 9.0. Its thermal stability was good, the enzyme activity of xylanase almost did not lose when it was kept at 50°C for 30 min, and the remaining activity was still 55% left even when it was kept at 85°C for 30 min. Then, through single factor and orthogonal array tests, the culture medium and the fermentation conditions were optimized as follows: 30% wheat bran, 70% corncob, 1% NH₄NO₃, the ratio of solid medium and water was 1:1.2, the optimum inoculum concentration was 1.5×10⁵ CFU/g dry matter. The highest xylanase activity was 2762 U/g dry matter under above conditions.

Key words: Thermophilic xylanase, Aspergillus niger, solid state fermentation, enzymatic characterization.