Study On Strain Selection And Optimized Conditions Of A Fungus Producing High Level β-Glucanase

In this paper,the highβ-glucanase strain was screened from the nature.Firstly it was studied the fermentation medium and cultivation conditions of this enzyme-producting strain and then the identification was done.In order to improve the ability producingβ-Glucanase,the strain was mutated by UV.Finally,the effect of fermentation process onβ-Glucanase production was studied by two-step fermentation.1.Based on the strains characteristic which is producingβ-Glucanase,the enrichment culture medium,the selective medium and the route of selection were designed.In different local collected soil samples,63 strains producingβ-Glucanase were obtained,and there were 11 stratins which the ratio of the clear zones to colony diameter was relatively great.By the second screening and fermentation shaker test,one strain which productβ-Glucanase activity was 16.34IU/mL,were chosen as the research object,named H₃₂₅.2.Based on the single factor experiment,the effect of different sorts of carbon,nitrogen resources and metal ions of inorganic salt,the optimization of fermentation medium of the strain H325 were studied.By the orthogonal experiment method,the composition of optimal medium was followed:oat powder 1.5g/100mL,corn syrup 2.5g/100mL,NH₄NO₃ 0.2g/100ml, MgSO₄0.02g/100mL,FeSO₄·7H₂O 0.01g/100mL,CaCO₃ 0.5g/100mL,Na₂HPO₄0.05g/100mL.On the optimal medium,β-Glucanase activity of the strain H₃₂₅ was 53.85IU/mL,increased by 229.56% than the initial medium.3.Of all sorts of capacity of 250ml shaking flask,the optimal cultivation conditions were liquid volume 50mL,initial pH 6.0,fermentation temperature 30℃,0.5ml inoculation amount containing 1.0×10⁶cells/mL,culture time 60 hours,Tween-80 0.1mL/100mL,β-glucan 0.05g/100mL.With the optimal conditions and the optimal medium,producingβ-Glucanase activity of the strain H₃₂₅ was 89.92IU/mL,increased by 450.31%than the initial medium and the conditions.4.The strain H₃₂₅ was primarily identified to be Aspergillus niger by the study of H₃₂₅ colony, mycelial and spore morphology.5.Treated by UV irradiation and selected in congo red nutritional identification plate,a forward mutation strain H_325-13 was obtained By fermentation shaker test.The productivity ofβ-Glucanase of H_325-13 was 85.38 IU/mL,increased by 2.97%than that of the initiak stain H₃₂₅.Subculture test indicated that the hereditary character of mutant H_325-13 was stable.6.Effect of fermentation process onβ-Glucanase production showed thatβ-Glucanase activity of the strain H_325-13 was 94.28IU/mL by two-step fermentation,while it was 11.36 enzyme-activity units by one-step fermentation.At the same time,the fermentation period was greatly shortened more than 22 hours to compare to one-step fermentation.