Study On Corn Straw Degradation And It's Hydrolyzate Fermentation For The Ethanol Production

Concerns about the soaring cost of fossil fuel and energy security have rekindled the interest in producing the substitute fuels from the renewable sources. There lies great interest of fuel ethanol production from lignocellulose owing to its sustainable and zero-omission characters. It holds a great hope and future to solve energy crisis for its resource saving and environment protecting. From this point of view, conversion of lignocellulose to ethanol is focused on in this thesis.Comprehensive research in transforming lignocellulose to ethanol had been accomplished basically: ascertainment of optimum conditions of pretreatment and enzymolysis, screening of cellulose-degrading strains with high performance, study on pure cultivation and co-cultivation.Comparing among the results elaborated the pretreatment condition by autoclaving: 0.75% H₂SO₄, solid-liquid ratio 1:20,130℃and 30min.Subsequently, those pretreated was saccharified through enzymolysis by cellulase and then fermentation proceeded by inoculating of yeast. Dynamic interaction between the quantity of cellulase and ethanol yield was found. Therefore, the following was considered to fit the cellulase best: quantity of 15mg/gDS, 50℃for 5h and at a speed of 150rpm. And two-day fermentation with 10% inoculation size of yeast was followed achieving the final ethanol yield of 0.163g/gDS.Screening the most wanted strains is the chief point of this thesis. Afrer primary screening by filter-paper Hutchison solid media and CMC solid culture medium,and further screening by filter-paper inorganic salt culture medium and Congo red culture medium with the CMC-Na as the only carbon source. 10 strains with high performance of degrading ability were picked out. According to their CMCA, FPA and the related properties, 6 strains with strong acidic cellulase activity were obtained finally and their highest enzyme yield time was on the 6th day. Ethanol yield rate of NSSF was up to 0.126g/gDS which was higher than that of SSF.To improve the sugar yield rate by straw-degrading microorganisms and ethanol yield rate via fermentation, further research on cross-feeding and fermentation by NSSF and SSF was carried out. Results indicated that the activity of cellulase excreted by cross-feeding of Aspergillus niger and Trichoderma koningi was the highest, with ethanol yield up to 0.139g/gDS by NSSF.In this process, a high red-pigment-yielding strain was obtained. Primary work on this strain and its pigment suggests that the strain merits further investigation for it will probably be a new way of straw utilization.