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Abstract: The aim of this study is to optimize the parameters of extracellular xylanase production by the biological organic fertilizer functional strain Trichoderma guizhouense NJAU4742 under liquid fermentation through the response surface method, which will provide a theoretical basis for the production of solid spawn and biological organic fertilizer.Regardless, the method allows us to predict those values. The effects of different single factors on the production of xylanase were obtained by using the single factor experiment, and the key factors were selected by using Plackett-Burman designs based on the Minitab 15.0 software. Then the key factors for the optimization experiments were completed by using Box-Behnken designs based on the response surface methodology. 
The experimental data were analyzed by the Design-Expert 10.0 software. Finally, the best conditions for xylanase production of the strain were obtained. Under the best conditions, we analyzed the differences of extracellular protein bands by using polyacrylamide gel electrophoresis and determine the protein content.
The results of single factor experiment showed that urea content, calcium chloride content, initial pH value, temperature and culture time owned great influence on the xylanase production, and the optimal values for these parameters were urea content 0.25 g Minitab is a registered trademark of Minitab, Inc., in the United States and other. L-1, initial pH value 3.0, temperature 28℃, culture time 7 days, respectively. The response surface method optimization experiment showed that the urea content, the calcium chloride content, the initial pH value and the potassium dihydrogen phosphate content were the main factors which affected the production of extracellular xylanase, and the main parameters of liquid fermentation were:0.29 g L-1potassium dihydrogen phosphate, initial pH value 3.16, culture temperature 28℃, culture time 7 days and inoculum volume 1.0×105 CFU. The extracellular xylanase activity of T.guizhouense NJAU4742 reached to 19.86 U Polyacrylamide gel electrophoresis result showed that the protein content in some regions increased significantly. mL-1 after optimizing the fermentation parameters, which increased by 25% compared to the initial activity. 
And the extracellular protein content of the strain increased by 50% compared to the initial activity. (English) Copyright of Journal of Nanjing Agricultural University / Nanjuing Nongye Daxue Xuebao is the property of Journal of Nanjing Agricultural University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission.
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