Study On Degradation And Fermentation Process Of Wheat Straw

Wheat straw resources are rich in China. But compared with corn straw and ricestraw, wheat straw is high content of crude fiber and low content crude protein,especially the lignin content higher; when directly used as feed, wheat straw is poorpalatability, nutrition value low, digestion and utilization rate low. According tonutrient characteristics of wheat straw, degradation and fermentation process of wheatstraw were studied in this research by reducing the lignin content and increasing thecrude protein content as breakthrough points; the purpose was to lay a foundation forwheat straw feed. This study was mainly selected a more appropriate degradationmethod and technological conditions for wheat straw by comparing degradationmethods and fermentation strains on wheat straw fermentation effect. The conclusionsare as follows:1. Wheat straw was degradated respectively by chemical reagent saccharificationand enzyme saccharifying test, which the results showed: In wheat straw chemicalreagent saccharifications, acidolysis saccharification was better than alkalinehydrolysis saccharification and hydrochloric acid saccharification effect was best;hydrochloric acid saccharification optimum technological conditions on wheat strawwere obtained by regression test: hydrochloric acid mass fraction18.66%, liquid-solidratio28:1(mL/g), saccharification time5days, the reducing sugar content25.22%. Insingle enzyme saccharification, the effect of xylanase saccharification on wheat strawwas the best; the xylanase saccharification optimal conditions were received throughorthogonal experiment: initial pH4.5, enzymolysis temperature40℃, w (enzyme): w(straw)=0.06, wheat straw concentration0.02g/mL, enzymolysis time24hours, thereducing sugar content33.55%. In compound enzyme saccharifying, the synergy effectof enzymes which compounded of cellulase, xylanase and pectinase were the best, setthe compound enzyme ratio as1:1:1, at pH4.0, temperature40℃, enzymolysis time16hours, the reducing sugar content35.19%. These could be concluded that the effect of enzyme saccharifying was better than the chemical saccharification, the compoundenzyme saccharification effect better than the single enzyme saccharification.2. In wheat straw fermentation experiments, the effect of the four strainsfermented wheat straw in the order: Aspergillus niger> EM bacterias> Trichodermaviride> Yeast, with Aspergillus niger fermentation effect on wheat straw was the best.Based on regression test, optimized the technological parameters of Aspergillus nigerfermentation on wheat straw, and the best parameter combination for the reducingsugar content and protein quality two indicators better was fermentation temperature29℃, inoculation amount2.55mL, fermentation time3days and12hours. Underthis condition, the reducing sugar content of wheat straw was2.13g/100g, proteinquality3.48g/100g.3. Wheat straw was degradated by using the compound enzyme whichcompounded of cellulase, xylanase and pectinase, and fermented by Aspergillus niger,the protein content in wheat straw after degradation was5.35g/100g, crude fibercontent38.15g/100g. Compared with no-treatment control, the protein contentincreased by2.41%, the crude fiber content was reduced by5.73%.To sum up, enzyme saccharification on wheat straw compared with chemicalsaccharifying had such advantages as enzyme quantity few, saccharification time short,environmental pollution slight, save resources, etc., so the enzyme saccharifying wasrecommended. Compound enzyme saccharification effect was better than singleenzyme, synergistic action of multiple enzymes could further improve the efficiency ofenzymatic hydrolysis and reduce the production cost. The effect of the Aspergillusniger fermentation was the best in wheat straw microbial fermentation. After wheatstraw was saccharified by enzymolysis, and used Aspergillus niger fermentation,which the straw through degradation and fermentation could further increase theprotein content, lower crude fibre content, enhance the flavor, improve the nutritionalvalue and so on.