Study On Production And Property Of Xylanase

As one of the most important enzymes, xylanase has wide applications in feed, food, textile, and paper industries.Xylanase production by Thermoascus aurantiacus and Aspergillus niger ZU-06 was studied using inexpensive agricultural wastes. The fermentation processes and enzyme properties were investigated and the main results were as follows:1. Xylanase production by Thermoascus aurantiacus was carried out under solid-state fermentation process. The results indicated that corncob and comhusk were good inducers for xylanase production. The culture medium and the cultivation conditions were optimized as follows: wheat bran 30%, corncob 33.4%, corn husk 33.4%, (NH4)2SO4 2%, carbamide 0.5%, KH2PO40.5%, MgSO4·7H2O0.2%, initial moisture content 65-70%, inoculum level of 10%((V/W). The high xylanase activity (10321IU/g koji) was attained after 5days at 45℃.2. Liquid fermentation process was performed to produce xylanase by Aspergillus niger ZU—06 . It was found that xylanase was inducible and the highest xylanase activity was achieved with 1% hemicellulose as carbon source and 1% bean cake as nitrogen source. The optimal C/N ratio and shaking flask speed were 4 and 200rpm, respectively. Addition of 0.3% glucose to the medium was helpful to produce xylanase. Under optimized conditions, xylanase activity reached 516IU/ml after 3 days at 30℃.3. High xylanase activity(8410IU/g koji) was obtained under solid state fermentation by Aspergillus niger ZU—06. The optimized fermentation parameters were as follows: wheat bran 40%, corncob 56.3%, NH4NO3 2%, NaNO3 0.5%, carbamide 0.5%, KH2PO4 0.5%, MgSO4·7H2O 0.2%, inoculum level 6%((V/W), initial moisture content in substrate 70% and culture temperature 30℃. The research results were available to reduce the cost of xylanase production.4. Xylanase produced by Thermoascus aurantiacus was stable up to 65 ℃ and its optimal temperature for enzymatic reaction was 70 ℃. The xylanase from Aspergillus niger was stable under40℃ and its optimal reaction temperature was 50℃. The optimal pH value was 4.8 for the reaction of xylanase from Thermoascus aurantiacus or from Aspergillus niger. Na+, Ca2+, Mg2+, Zn2+ were the activators and Fe3+, Mn2+ were the inhibitors for the two kinds of xylanase.5. Xylanase produced by Thermoascus aurantiacus could hydrolyze xylan into xylo-oligosaccharide with the average degree of polymerization of 3—10 within four hours. By the xylanase from Aspergillus niger ZU—06, the average polymerization degree of xylo-oligosaccharide was 3.6 after half an hour. The hydrolysis results by xylanase provided a good experimental foundation for industrial production of xylo-oligosaccharide.