| As a crucial components of hemicellulose, xylan is the most abundent living resources that can be recycled in nature except of cellulose. Xylanase is the enzyme family that dehydrates xylan into xylose or oligoxylose, which has extensive application in industries such as animal feed, food, fabric and papermaking. So researches of xylanase by microorgansim has become one of the hot spots of modern fermentation industry and enzyme preparation industry. In this paper, a xylanase production fungi Aspergillus niger C-2 was studied, which included optimization of solid-state fermentation condition such as cultivating environmental factors and culture compositions. The application and characterizations of xylanase were studied, too. The main results were as follows:1. The culture medium and cultivation conditions for xylanase production of Aspergillus niger C-2 under solid state fermentation were optimized. The results confirmed that the optimum culture medium was composed by wheat bran and cormcob at the ratio of 1:1, (NH4)2SO4 2%, urea 3%, KH2PO4 0.1%,TW-80 0.3%,initial pH 7.0, and ratio of optimal carbon source and water 1:1.4. The optimum cultivation conditions included culture load 20g in 500mL flask, inoculant volume 2mL with spores of 109cfu/mL, after the inoculanted culture was fermentated for 42h at 30℃, the fermentated culture yielded xylanase with hightest activity of 10068U/g.2. Some characterizations of xylanase were studied. The opimum pH value of xylanase was pH4.4～4.8, which was stable over pH4.5～6.5. The remained emzyme activity was over 95% after treatment 6h under pH4.5～5.5. The optimal temperature of xylanase was 50℃. The activity of xylanase was increased by Cu2+, Mg2+ and Na+, decreased by Ca2+, Fe3+, Mn2+, Ag+, K+ and Fe2+, and not effected significantly by Zn2+ and EDTA. Five oligoxyloses were founded in the extracts of the fermented culture.3. The optimal solid-state fermentation condition of Asp. niger C-2 on trays was: solid inoculant 0.5%~0.75%. culture load 300g to 400g with culture thick 3cm~4cm, and the ratio of materiel and water was 1:1.8. Xylanase activity was increased significantly by water suplement during the fermenting process. The fermented culture was dried at 60℃when the fermentation had been carried for 40h. The lost of xylanase activity was less than 15% even if the xylanase preparation was treated for 1h at 80℃~90℃.4. The polit-scale production of xylanase with solid-state fermentation was performed on charging trays and in machine of solid-state fermentation. When fermenting in charging trays, the mycelia growed slowly and was contaminated easily, the activity of xylanase in the fermentated culture was 4234U/g. When fermenting in machine of solid-state fermentation, the inner temperature of culture was so high that the mycelia couldn't grow, which resulted only 300～3622U/g xylanase activity in the fermentated culture. when the mycelia culturing was in charching trays and the enzyme fermenting was in machine, respectively, the limitations above were avoided, and the final xylanase activity of Asp. niger C-2 culture was reached 7461U/g.5. Feeding experiments in young pigs were performed using enzyme preparation product and xylanase preparation. Results showed that xylanase preparation increased weight 11.8% and decreased 8.8% of ratio of feed to meat. |
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