| Wheat bran is the by-product of wheat milling, which is composed of episperm, peel and aleurone. And it contains some starch, protein, cellulose and hemicellulose. In addition, there are 0.4～0.7 g ferulic acids in 100 g wheat bran, importantly, these acids mostly bound in bran in the form of covalent linkage with cell wall polysaccharides. Therefore, wheat bran is good material for preparation of dietary fiber (DF) and feruloyl oligosaccharides (FOs).In this study, wheat bran was used as the material, DF and FOs was obtained by submerged fermentation of edible mushrooms. The comparison of different mushrooms' growth rates, biosythensis of enzymes and the production of DF and FOs from wheat bran were carried out, and then the optimal strain for fermentation was screened out. Effects of culture medium and fermentation conditions on yields of DF and FOs, and on biosythensis of xylanase were investigated. The mechanism of DF and FOs preparation by fermentation was revealed by detecting the enzymes secreted by mushroom in different culture conditions. FOs were puried by precipitating of ethanol, absorption of resin and chromatography of column. The compositions and structures of FOs were analyzed through HPLC, GC, IR and MS. Lastly, the biological activities of DF and FOs were studied, their antioxidant and antitumor and effects on the growth of intestinal microorganisms were compared. The main results and findings were shown as follows:1. Agrocybe chaxingu, the common edible mushroom, was suitable for the preparation of DF and FOs. The yield of DF reached 68.49% after fermentation,of which, SDF was 19.24%. The production of FOs by fermentation was the highest yield among these edible mushrooms, and it was 35.4μM.The growth rates of mushrooms in medium of wheat bran and PDA were determined, and results showed that all of the mushrooms grew well in these medium, and the growth rate in wheat bran was higher than that in PDA medium. Hericium erinaceus and Pleurotus ostreatus were the best strains, which grew well in wheat bran medium. Enzymes detection indicated that mushrooms used in our study could secrete amylase, protease, cellulase and xylanase. Hericium erinaceus also could secrete ferulic acid esterase, which was the first reported to our knowledge. The activities of these enzymes were different from the species of the mushrooms. Agrocybe chaxingu was the only strain, which could secrete higher amylase, protease, cellulase and xylanase during fermentation. In the end, the correlation of DF and FOs production with activities of enzymes was analyzed, and results proved that correlation between DF yield and cellulase activity was negative effect (r=-0.711), and xylanase activity positively influenced FOs production (r=0.912).2. Effects of nitrogen source and inorganic salt on the quality of DF were investigated. Results showed that yeast poast, MgSO4·7H2O and VB1 influenced DF quality positively. And then the optimal additions of the three substances were optimized by D-Optimal design, and results were analyzed by Design Expert. The optimal fermentation medium was determined:under the condition of 2.50 g/L yeast posat,1.10 g/L MgSO4·7H2O and 0.14 g/L VB1 in wheat bran of 50 g/L, the best quality of DF, which contains 22.3% SDF in total DF, was obtained.The culture conditions of fermentation temperature, volume capacity, pH and inoculum quantity and fermentation time influenced DF quality effectively. The effect of volume capacity on DF quality was linearity. DF quality decreased with the increase of volume capacity, and the optimal value was 60 mL/250 mL. The influence of inoculum quantity on DF quality was similar with the effect of pH on DF, both curves fitted well with Guass equation. By analyzing the experiments' results, the optimal culture condition was obtained. Under the condition of fermentation temperature 25℃, volume capacity 60 mL/250 mL, pH value 5.5, inoculum quantity 12% and fermentation time 6 d, the best quality DF was obtained, and it contained 24.83% SDF.Effects of culture conditions on the secretion of enzymes from Agrocybe chaxingu during fermentation were investigated, results indicated that activities of amylase, protease and cellulase were increased under the optimal medium and condition. Among them, amylase and protease improved by 30% and 20% than the based medium, respectively, and cellulase of C1 got up to 145% of the initial activity.3. Effects of medium components on the bio-synthesis of xylanase and FOs yield were studied, and results showed that carbon and nitrogen source could regulated the yields of xylanase and FOs secreted by Agrocybe chaxingu. Glucose, lactose and peptone improved the bio-synthesis of xylanase, and their additions influenced the enzyme activity effectively. The best additions of glucose, lactose and peptone were 15 g/L,15 g/L and 1 g/L, respectively. Under this medium, the yield of 0.335 mM FOs and 1.27 U/mL xylanase was produced.Volume capacity and fermentation time influenced the bio-synthesis of xylanase significantly; and the activity of xylanase first improved and then decreased with the increase of volume capacity. With the prolonging of fermentation time, the biosynthesis of xylanase first increased and then unchanged. The influence of culture condition on FOs production was not as same as the effect on bio-synthesis of xylanase, especially, the effect of volume capacity. For FOs, the yield was decreased with the increase of volume capacity. FOs yield first improved and then decreased with the raise of pH, increase of inoculum volume and prolonging of fermentation time. Under the conditions of volume capacity 90 mL, inoculum quantity 12% and pH 5.5, and feremtnation time 6 d, the highest yields of FOs (0.428 mM) and xylanase (1.36 U/mL) were obtained.The structure of wheat bran fiber before and after fermentation by Agrocybe chaxingu was detected by scanning electron microscopy. Results indicated that the fiber structure changed significantly by fermentation. Originally, the fiber combined tightly with smooth surface, while, they were not smooth and broke dnown after fermentation.4. The FOs were isolated and purified by precipitation of ethnol, absorption of resin Amberlite XAD-2 and Sephadex LH-20. Results showed that concentration of ethnol influenced FOs precipitation significantly. FOs started to precipitate when ethnol concentration was higher than 50%. The precipitation of 60～90% ethnol increased the growth of lactic acid higher than the precipitations under other concentrations. And then, the precipitation of 60～90% was purified by Amberlite XAD-2 and Sephadex LH-20, and three components of FOs were obtained. The analysis of FOs'structure showed that they were composed of xyln, arabinose and ferulic acid, and the degree of FOs-1 was 3 to 6, FOs-2 degree was 1 to 3 and FOs-3 was 0 and 3.5. The physical characteristics of IDF were improved by fermentation. The water hoding power, swelling ability and oil hoding power of IDF increased by 8.85%,23.13% and 15.21%, respectively. The adoption of bile salt was also improved by fermentation.DPPH radical-scavenging activities of FOs and SDFs were higher than 60%. The hydroxyl radical scavenging activity of SDF from wheat bran was the highest among FOs and other SDF samples, the inhibition rate was 89%, followed by FOs and SDF-Out. The FOs have the highest antioxidant capacity among SDFs and FOs, followed by SDF-In and SDF-Ou, while the lowest was SDF-0. In a word, both SDFs and FOs showed high antioxidant ability.FOs and SDFs could increase the growth of lactic bacteria and influence the growth of E. coli and Staph. aureu. FOs-2 was the best among them, which only increased the growth of lactic bacteri, but also inhibited the growth of E. coli and Staph aureu. SDF-Out could increase the growth of lactic bacteri and inhibit the growth of E.coli, there was no function on Staph. aureu.MTT assay was used to analyses the effects of FOs and SDFs on human colon cancer cell of HCT-116. Results indicated that both FOs and SDFs could inhibit the growth of HCT-116, and the inhibition of FOs was higher than SDFs, especially FOs-1. The inhibition of HCT-116 reached 54.7% when the concentration of FOs-1 was 1 mg/mL. SDFs obtained by fermentation inhibited HCT-116 higher than that from wheat bran, and the inhibition was 45% when their concentrations were 1 mg/mL. Morphological observation of HCT-116 cell after treated by FOs-1 showed that cellular shrinkage to round, and cell floated, therefore, the cell closing to wall decreased.
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