Screening Of Strain Producing β-Glucosidase And Studies On The Induction Effects Of Corncob

β-glucosidase is one of the components of cellulase. It is important in cellulose-degrading for it can remove the inhibition of cellobiose in the EG and CBH. It also has wide applications in food industry for releasing the aromatic compounds and removing the toxic substances in the raw materials. In this study, A. niger 60B-3D was selected through protoplast mutation, using the A. niger 3-3M as parent strain, which was got from ultraviolet irradiation mutation. Several carbon sources were compared to produce this enzyme and the corncob was found to be the best inducer for P-glucosidase production. Then the induction effect of corncob was studied for relevant reports were rare. The main results were as followed:1. Aspergillus niger CGMCC 3.316 was selected as the parent strain, a mutant 3-3M was screened after ultraviolet (UV) irradiation. Theβ-glucosidase activity of A. niger 3-3M was 19.5±1.0 IU/mL, improved by 15%.2. The conditions of protoplast formation and regeneration of A. niger 3-3M were also studied. The mycelium was collected after culturing on the cellophanes for 24 h in the PDA plate, then was treated with 10% snailase (5 mg/mL) and cellulase (5 mg/mL) for 4 h at 32℃, using 0.6 M NH4C1 as the stabilizer and the citrate acid buffer as buffer system. The regeneration medium was Cazpek's medium with 0.6 M NaCl as stabilizer.3. The protoplasts of 3-3M were mutated with UV and a mutant 60B-3D was screened. Theβ-glucosidase of 60B-3D was 23.4 IU/mL, with an improvement of 23% comparing to the A. niger 3-3M. The fermentatio process of mutant was also studied. It was found that the mutant could secrete more protein than the parent strain.4. The maximumβ-glucosidase acitivity of 60B-3D reached 63.86 IU/mL after carbon and nitrogen optimization. Corncob was found to be the most efficient carbon source, and the proper nitrogen source were the combination of yeast extract and ammonium sulfate.5. Several carbon sources were compared to produceβ-glucosidase in A. niger 3.316 and corncob was also found to be the most efficient carbon source. This result was consistent with that we had got in the case of A. niger 60B-3D. So the induction effect of corncob was further investigated. The results showed that the soluble parts of corncob (WS) could induce theβ-glucosidase production and the concentration of WS had little impact on the induction effect. The water insoluble residual part of corncob (WIR) was also found to be beneficial forβ-glucosidase synthesis in A. niger 3.316.