Study On Saccharification Of Wheat Bran Fiber And Hierarchical Utilization

Wheat bran is the main by-product of wheat flour, which is about14-17%of wheat grain.The comprehensive utilization rate of wheat bran is low for which is mainly used for feed and fermentation industry and fiber is hard degradation now. Therefore stduies for promoting the utilization of wheat bran have important practical meaning.In this study, wheat bran is a raw material for the purpose of enhancing utilization value. Wheat bran protein was extracted by alkali solution, and nutritive compositions were measured; wheat bran fiber was enzymatic saccharification by a combined treatment of xylase and cellulase prepared with fermentation; saccharification of wheat bran fiber using steam explosion combined enzymatic hydrolysis, and microwave acid hydrolysis; malic acid was prepared by fermentation of wheat bran sugar, and the fermentation conditions was optimized; arabinose was enriched preparation by fermentation using wheat bran fiber sugar; and finally the benefits of wheat bran was analyzed using a comprehensive utilization factory.The main results and conclusions obtained are as follows.1. Wheat bran component was analysised and showed that there were12.80%starch,18.51%protein and45.40%wheat bran fiber. enzymatic hydrolysis condition of starch and protein extraction condition were optimized, which showed the protein extraction reached the maximum of15.85%at pH12, solid-liquid ratio1:15,50℃and time of3h and precipitation pH3.8. There were4.42%of albumin,2.92%of bran globulin and3.29%of gliadin,4.79%of glutenin and2.97%of insoluble protein, and a high nutritional value with20.75%of essential amino acid content compared the protein quality,37.04%of E/T value. Wheat bran fiber reached70.27%after removing starch and protein.2. An efficient cellulolytic strain M9was selected from mutation Trichoderma viride with Co-60irradiated, and the culture condition was optimized which were composed of wheat bran fiber of3g, solid-liquid ratio of1:7.5, initial pH6.0, fermentation time96h, inoculation of4%. Cellulase activity of the strain M9produced reached1.90u/mL. β-glucosidase was separated and perificated with salting out, DEAE-52and Sephadex G-75chromatography, its molecular weight of59.8kDa and128.93times of activity than the initial. The β-glucosidase maintained a high activity and stability at pH5.0and50℃, and the activity was enhanced the activity with Mg2+, Tween80surfactant and inhibited with Fe3+, Cu2+and SDS. Enzymatic saccharification conditions of wheat bran fiber were optimized by a combined treatment of xylase and cellulase:the substrate concentration2g/40mL, temperature50c, pH5.0, time of8h, and concentration of the sugar solution reached9.70mg/mL at this condition.3. Wheat bran fiber structure was destroyed obviously with steam explosion pretreatment, especially significant degradation of cellulose and hemicellulose; pH of WBFSE reduced and its color deepened with the steam pressure increased; degrees of crystallization was enhanced with fiber structure degradation of WBFSE; reducing sugar and glucose concentrations increased significantly with eneymatic hydrolysised, but decreased with steam pressure increased, xylose concentrations decreased and little relationship with the pressure of the steam explosion.4. Microwave power, hydrolysis time and acid concentration played remarkable impacts on the saccharification of wheat bran fiber. Saccharification conditions were optimize by response surface methodology:sulfuric acid concentration of1.86%, hydrolysis time36min and microwave power350W. In this condition, the xylose got maximum of4.86mg/mL and total sugar12.91mg/mL. Hemicellulose of WBF was dissolved, and degrees of crystallization was enhanced with the cellulose exposed, even partially dissolved when the microwave power increased to600W; lignin did not change obviously.5. The fermentation culture mediums of malic acid were optimized with response surface methodology, which was composed of magnesium sulfate0.17g/L, ammonium sulfate2.34g/L, calcium carbonate70g/L and temperature of31℃with the wheat bran sugar. In this condition, the malic acid production reached a maximum concentration of15.73g/L. A Pachysolen tannophilus was screened for fementation of wheat bran fibers sugar, and arabinose content reached5.93g/L,62.10%of the sugar after72h cultivated. The purity of arabinose reached90.80%with recrystallized under the temperature of4℃after decolorization, desalting and concentration prtreatment.6. Wheat bran utilization was analyzed with a factory of5000t processing capacity as example, as well as technology route of protein、sugar and malic acid were designed. Economic benefit was analyzed through material calculation, and the statistical result showed that deep processing of wheat bran could bring a certain profit.