The Optimization Of Production, Purfication And Application Of Xylanase From Aspergillus Niger S33

A Xylanase strain isolated from a soil sample was explored the optimization of liquid-state fermentation condition and proteins purification; analyzed the characterization and application on steamed bread of its pure Xylanase enzymes. The main research conclusions are as follows:The Xylanase strain S33 was identified as Aspergillus niger, which isolated from a soil sample and produced a highest Xylanase activity with 132 U/ml than others candidate strains. The results of single-factor-experiment on Liquid-state fermention revealed that 3% corn cob,0.5% urea, initial pH5.0 and cultivation temperature of 45℃were the optimal conditions for the Xylanase production. After 4 days cultivation under the optimal conditions, the Xylanase activity and specific activity can be achieved to 398 U/ml and 1206 U/mg respectively, which belongs to a higher xylanase production based on the internal reports so far. It could be improved the possibility of future industry production as the utilizing low-cost corn cob and urea as carbon and nitrogen source respectively under submerge fermentation.The Aspergillus niger S33 was deemed to a kind of acidic strain, which can produce a higher Xylanase activity under pH 4.0-7.0 condition, and be stable even in 50℃cultivation condition with 82% residual activity as compared to the optimal temp 45℃. As a non-thermophilic fungi, the Aspergillus niger S33 will be worth to further study.By using the ammonium sulfate precipitation method to collect the most proteins from culture broth, the aimed Xylanase band with～54 kDa was purified successfully by DEAE and Source S ion-exchange chromatography. The final purification resulted in a yield of 12% of the activity and a 3.38-fold increase in specific activity. The specific activity of the purified xylanase was 4051.3 U/mg.Xylanase is optimally active at 65℃and pH 4.0, and can be stable in the range of pH4.0-8.0 within 50℃. The Hot deactivation dynamics analysis indicates the inactivation rate of xylanase under different temperature is:0.022 (50℃),0.087 (60℃),0.126 (70℃); the activation energy in reaction is about:114.32 kJ. In the research of steamed bread quality effects that the xylanase addition could effectively improve the volume and decrease the hardness of steamed bread, but no effects on the inter water content. The suitable dosage of xylanase can increase the final score as well, but prevent the hardness depravation of steamed bared while storage.