Ethanol Production From Corn Stover Using Simultaneous Saccharification And Fermentation(SSF) After Ionic Liquid Pretreatment

The production of fuel ethanol by lignocellulosic resource has become a hot spot in the new energy development. With the advantages of environment friendly and renewable, fuel ethanol will play an important role in the energy needs of future society. The straw is a rich resource, and it's bioconversion to fuel ethanol is very meaningful in the development of economy and society.In this paper, corn stalks are used as raw materials, the pretreatments of which by alkali, enzymatic and ionic liquids respectively were used to compare the ability of lignin removal and effect on enzymatic saccharification. Then the impact of various factor on the simultaneous sacchrification and fermentation were studyed to obtain an appropriate production process of ethanol fermentation.The results of pretreatment showed that: alkali can reduce lignin effectively and improve the conversion rate of enzymatic hydrolysis. Under the conditions of treatment(alkali concentration of 3%, 120℃, 1h), the extrusion rate of lignin in Straw is 91.8%, cellulose content compared with untreated samples has almost doubled. Reducing sugar concentration after enzymatic hydrolysis is four times as much as before. Enzymatic pretreatment by laccase may reduce lignin, but it has inhibitory effect on the enzymatic hydrolysis processes. [BMIM]Cl can effectively dissolve and regenerate cellulose, and the higher the temperature, the shorter the time required for dissolution. The maximum solubility is obtainded at 100℃. Polarized light microscopy observation and infrared spectra analysis found that the ionic liquid processing method only causes swelling of cellulose and the destruction of intermolecular hydrogen bonding but no derivation reaction to cellulose. Hydrolysis rate of regenerated cellulose was significantly increased, the reducing sugar is twice more than that of untreated samples after the hydrolysis of 5h. The results of simultaneous saccharification and fermentation showed that: The optimum conditions are temperature 35℃, liquid ratio 1:15, the initial PH value 4.8, enzyme concentration 40 U/g, inoculation 0.025 g/g, added nitrogen source (yeast extract 0.3 g/L, peptone 0.5 g/L), pre-hydrolysis time15h. Under these conditions, ethanol concentration is up to 16.67 g/L. The alcohol concentration of regenerated straw retreated by [BMIM]Cl under the same conditions with high substrate concentration (solid-liquid ratio of 1:6) simultaneous saccharification and fermentation is up to 47.73 g/L, which reaches 91.3% of the theoretical value and indicates a good application prospect.