| Cellulose and hemicelluloses, the main composition of the plant cell wall, exists widely in the nature and is the most abundant reproducible bio-polymer in the earth. In view of the high efficiency and the environment protection, the degradation catalysed with enzymes is the most effective way to hydrolyze cellulose and hemicellulose thoroughly and causes no pollution.β-mannanase, xylanase and cellulase provide obvious advantages for the applications in the processes, such as in laundry detergents, paper pulp bleaching and hydraulic fracturing of oil well. In recent years, the research forβ-mannanase, xylanase and cellulase has been extensively studied. In this thesis, the composition medium of solid-state fermentation, which used apple pomace and cottonseed meal as carbon source for Aspergillus niger SL-05 producing extracellularβ-mannanase, xylanase and cellulase, was optimized and characteristics of these three enzymes were extensively studied. The main results are as follows:1. Medium compositions for Aspergillus niger SL-05 producing extracellularβ-mannanase, xylanase and cellulase were optimized in solid-state fermentation using single factor experiments and statistical experimental designs. The optimal medium forβ-mannanase production contained apple pomace and cottonseed meal (1:1) as carbon and nitrogen sources, 2% urea, 2% glucose, 0.12% KH2PO4 and 60% initial moisture content; the optimal medium for xylanase production contained apple pomace and cottonseed meal (1:1) as carbon and nitrogen sources, 2% urea, 2% glucose, 0.06% KH2PO4 and 65% initial moisture content; the optimal medium for cellulase production contained apple pomace and cottonseed meal (1:1) as carbon and nitrogen sources, 2% urea, 2% glucose, 0.09% KH2PO4 and 62% initial moisture content. Under optimized conditions,β-mannanase production of 296 Units/g (U/g) dw, xylanase production of 6347 U/g dw and cellulase production of 66032 U/g dw can be achieved, which were improved 61%, 49%, 53% compared with that of the initial medium, respectively.2. The growth kinetics of Aspergillus niger SL-05 were investigated. The results showed that the optimal fermentation time for xylanase production under the optimized conditions would be 48 h. As spores were produced after 48 h, the enzymes production tended to be slower. The major enzymes secretion was observed during 24-48 h of inoculation with high cellular metabolism activities. In this period, the amount of total sugar and reducing sugar decreased dramatically, the pure protein increased rapidly, the pH value of the medium decreased, and the dry weight loss rate increased distinctly. Then, small increase in enzyme secretion was found. Compared with the amino acid content before fermentation, the content of most amino acid increased after fermentation, especially limiting amino acids: Lys, Met and His, which were improved 38%, 85%, 69% compared with that of the initial medium, respectively.3. The effects of the optimal temperature, pH, thermal stability, stability of acid and alkali, common metal ions to enzymes were researched. The results showed that theβ-mannanase, xylanase and cellulase were acidic enzymes and the optimal pH were 5.0, 5.0, and 4.5, respectively. Three enzymes all remained above 85% of the initial activity after incubated at pH3.5-6.0. The optimal reaction temperature were 80℃, 55℃, 75℃, respectively. Thermal stabilities ofβ-mannanase and cellulase were high. They remained above 80% of initial activity afterβ-mannanase incubated for 5 h at 50℃and cellulase incubated for 30 min at 60℃. But xylanase remained only 17.35% after incubated for 30min at 60℃. The Km and Vmax of theβ-mannanase were obtained, which were 0.083μmol/mL and 166.67μmol/min, respectively. The activity of the mannanase was inhibited greatly by Cu2+(91%) and was activated by Fe2+, Fe3+ and Mg2+, especially Fe2+(127%). The activity of mannanase was inhibited by 0.5 mM Ca2+; however it was activated at 1.0 mM Ca2+.
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