Study On Fermention Of Corn Stover To Produce Dietary Fibre By Fungi And Its Bioactivity

Dietary fiber, as an erxtremely important functional food, has gained extensive attention of the nutritionist at home and abroad very much. In the development of functional food, dietary fiber has been payed high priority. Dietary fiber is a mixture including cellulose, hemicellulose, lignin and souble polysaccharide. Corn Stover are rich in dietary fiber components and resources in china, but, has not been fully utilized.Microorganisms were isolated ,which producted dietary fiber from collected soil samples.18 highly active cellulolytic strains were isolated with selection medium. By flask culture , determination content of DF in broth. Finally, selected strain JZ-11 of high levels DF in fermentation broth. It was found to have visible fungal characteristics by morphology.Strain ZJ-11 carried out on the optimization of culture conditions. The Plackett-Burman design was used to evaluate the effects of eight variables which were Corn Stover powder, peptone, KH2PO4, tween-80, urea, MgSO4, CaCl2 and NaCl. By analyzing the statistical regression, cellulose, soybeanmeal and (NH4)2SO4 were found to be the most important factors.Subsequently, Response surface methodology was employed to determine the maximum cellulase activity at optimum concentration of key factors. the maximum cellulase activity was found to correlate to the three parameters that could be represented by second-order polynomial models. The optimal values of the three parameters were determined as 23.28g/L Corn Stover powder,12.77g/L peptone and 1.27g/L tween-80. the contents of TDF was 400.20mg/L and the actual experimental result was 394.20mg/L. The predictive value is in good agreement with the actual value. TDF content increased 17.64% than the initial value. Study the fermentation conditions of strains ZJ-11 with single factor experiments. The results show that the optimal incubation temperature was 30℃,the optimal initial PH was 6, the optimal rotation speed was 150r/min, the optimal inoculum was 8%, the optimal culture time was 144h. At this time, the TDF content of 401.91mg/L.The DF of corn stover has a high scavenging activity on·OH and O2-·free radical. The IC50 was 7.66mg/mL, 8.25mg/mL respectively. It has scavenging action to DPPH, the highest percentage was 10.55%. The result of dietary fiber adsorbed bile acid in vitro indicated that the DF of corn stover had adsorptive capacity to the bile acid and the adsorptive capacity was 22.74mg/g, the returns-tatio of bile acid was 97.97%.The acute toxicity tests on Corn Stover DF. The results show that the mouse lethal dose of Corn Stover DF is greater than 15g/kg, are non-toxic level.