Solid-state Fermentation Of Aspergillus Niger And Study Of The Enzymatic Characteristics

The paper uses three-point method and the interpolation method to abserve the colony morphology , external hyphae and spores of the laboratory-preserved Aspergillus niger SB-02. It is studied the Aspergillus niger SB-02's degradation of xylan on double-deck plate and determinated the activity of xylanase after 3 days liquid fermentation.The paper focus on optimization of the solid fermentation conditions for xylanase. Optimization factors are as follows: carbon, nitrogen, temperature, incubation time, the initial pH , the initial moisture, inoculation, extraction, etc. The results show that: the bran and corn-cob are mixed at ratio 7:3 as a mixtured carbon source; the best inorganic nitrogen source is ammonium sulfate(0.15%); the ratio of the materials and the water is 1:1 ; the appropriate culture temperature is 28-30℃; the initial pH is 4.8; the appropriate inoculation is 4% (107 / ml); the content of Tween-20 is 0.05%; the liquid fermentation time is 72 hours; 10 times the medium of water, extracted for 1 hour at 40℃; the activity of xylanase is up to 650.45 U/ml.The crude enzyme powder is made from extraction,filtration,centrifugation,ultrafiltration, freeze-dried of the solid-state fermentation. The results show that: the crude enzyme powder contains various degrading enzymes,such as xylanase, cellulase, filter enzyme, amylase; respectively,their activity is 66.3%, 17.1% and 3.8% , 12.7%; the optimum reaction temperature of the crude xylanase is 50℃and the optimum reaction PH value is 4.8; Fe3+ strongly actived the activity of the xylanase; Mg2+ has a certain inhinition ; the Other metal ions have no significant role.After dextran gel chromatography of DEAE A-25 ,we found that Aspergillus niger xylanase contains three isozyme: X-Ⅰ, X-Ⅱ, X-Ⅲ. X-Ⅲis not a adsorption component; the content of X-Ⅰ, X-Ⅱare fewer than X-Ⅲ. After PAGE ,three isozymes all showed a single band. After purification, Xylanase activity increases 2 times and enzyme recovery is 26.3%.