Breeding And Solid-state Fermentation Of High Acidic β-mannanase Producing Aspergillus Niger Strain

The research started from naturally isolating a parent strain Aspergillus niger LW-1 which could produce acidicβ-mannanase. Then put it through vacuum microwave irradiation and Ethyl Methane-sulfonate for processing. By basic madium solid-state fermentation and multi-gerneration cultivate and screening obtain a high-yield and stableβ-mannanase on producing strain Aspergillus niger E-30 The enzyme activity of this strain reached 36675 U/g which was 2.15 time the original strain yield(17048 U/g). The enzyme activity of E-30 remained stable after two-month storage.And theβ-mannanase produced by Aspergillus niger E-30 is acid enzyme, which has been proved by the optimum and stable pH experiment.Using Aspergillus niger E-30 as a parent strain to improve the condition in solid-state fermentation. In order to test the impact of different organic carbon resource mixing ratio,different konjak powder and corn steep quantity, different inorganic nitrogen resource and it's quantity, KH2PO4 quantity and different C/N ratio,designed singgle factor method and orthogonal experiment. The best culture medium contains the following: soybean cake powder 1.0 g, corn powder 0.9 g, wheat bran 8.1 g, konjak powder 0.7 g, NH4NO3 0.185 g, CaCl2 0.0125 g, MgSO4 0.0125 g, KH2PO4 0.036 g, and 1:1.7 material-water ratio.The best culture circumstance is: 33℃for 96 hours. The enzyme activity of the highest yield strain reached 55876 U/g, which was 1.52 time the original 36675 U/g.Based on the optimal flask culture medium and ferment conditions, koji plate fermentation for Aspergillus niger E-30 was studied comprehensively. The process curve of koji plate fermentation which include enzyme activity of acidicβ-mannanase, water contents, oligosacchardies contents, pH of material and temperature of central medium had been designed after 108 h fermentation. The most suitable conditions in koji plate fermentation were found after several experiments. The strain Aspergillus niger E-30 showed high and stable acidicβ-mannanase activity (48923 U/g) with the conditions of 20% water increase in medium, oxygen input quantity increase in pre-72h, Temperature adjustment from 33℃to 30℃after 48h and natural pH.