Study On Fuel Ethanol Production From Corn Stover Hydrolyzate By Fermentation

Development of fuel ethanol industry is helpful to solve the energy stress, reduce environmental pollution, and promote agricultural progress and new rural construction. In this thesis, the research progress of fuel ethanol production by hydrolysis and fermentation of biomass was summarized, components of corn stalks and acid hydrolysate were analyzed, fermentation performance of five strains were compared and then the best one for hydrolyzate fermentation was chosen, Thermotolerant Saccharomyces cerevisiae was screened by domestication whose inhibitor tolerance was analyzed and finally a strain was domesticated, which was able to adapt to the hydrolysate fermentation for high-yield ethanol.In the fermentation comparison of Saccharomyces cerevisiae, Neurospora sitophila, Neurospora intermedia, Candida shechatae and Pachysolen tannophilus with glucose as the single carbon source, Saccharomyces cerevisiae was best for the highest ethanol yield and the shortest log phase with 6～13 h, which was considered for hydrolysate fermentation.By domestication, a heat-resistant strain was screened out, which performed normal growth under 42℃. By optimizing, the fermentation conditions were determined for 30℃, 150 rpm, initial pH 5.0, inoculation amount 10 %. Thermotolerant Saccharomyces cerevisiae could not be directly used for the hydrolysate fermentation, which needed domestication.Results showed that, the maximum inhibitor-tolerated concentrations of Thermotolerant Saccharomyces cerevisiae were formic acid of 2.0 g/L, acetic acid of 5.0 g/L, furfural of 8.0 g/L, respectively; Biomass yield and formic acid concentration (0～3.0 g/L) almost represented a linear relationship; Inhibition of formic acid, acetic acid and furfural were decreasing; to improve the ethanol yield of hydrolysate fermentation, inhibitor content should be minimized, especially formic acid.Through hydrolysate gradient domestication, a strain was screened out, which accommodated hydrolysate fermentation with ethanol yield of 79 %, glucose-ethanol conversion rate of 40 %, and high temperature resistance.