Study On The Ethanol Fermentation From Filtered Saccharified Liquor Of Cassava

Bio-ethanol is regarded as one of the most promising bio-fuel from renewablesources. With increasing oil price and global environmental concerns, bio-ethanolproduction has recently become a focus of attention. The heavy use of food crops assource materials for fuel ethanol will lead to the shortage of food and fodder and therise in food crops price, which is also directly affecting the national food security.Now cassava used as a kind of non-food crops by bio-ethanol plants is considered aparticularly attractive raw material for bio-ethanol production, which is inexpensiveand unaffected by food and feed shortage concerns. Cassava must firstly be liquefiedand saccharified, and then can be used as a substrate for ethanol fermentation. Thehigh viscosity of liquefied or saccharified liquor has a dramatic impact on materialsfluidity in the reactor, therefore it is difficult to stir, heat and cool for fermentedliquid. The impurities of cassava flour will lead to block pipes and equipments andcleaning difficulty, which also causes a series of problems, such as, the mixedbacterium affected and the acidity rised. In this paper the liquefied and saccharifiedof cassava and fermentation broth produce ethanol were studied. By using filteredsaccharified liquor, the viscosity of fermented liquid and the solids content offermented liquor can be reduced greatly, and the liquidity of fermentation liquid canbe increased significantly. At the same time, it also reduces the impact of impurityon equipment and the whole production process.The operation conditions of liquefaction and saccharification were studied. Theeffects of liquefaction enzyme dosage and the temperature in the process ofliquefaction were investigated. Finally the optimum conditions were found asfollows: the dosage of liquefaction enzyme was20u/g, and the temperature ofliquefaction was95℃. The effects of saccharification time, saccharificationenzyme dosage and the ratio of water to material in the process of saccharificationwere investigated under the conditions of liquefaction. The effect of the ratio ofwater to material on fermentation was also studied. The optimum conditions ofsaccharification process were obtained via response surface methodology (RSM) on the basis of the experiments of the single factors. The conditions of saccharificationprocess were as follows: the dosage of saccharification enzyme was200u/g cassava,and the ratio of water and cassava was2.5∶1, then the time of saccharification was105min.The saccharified liquor was prepared based on the above optimum conditions.The filtrate was used for ethanol production. Fermentation conditions had beenstudied, including fermentation time, the amount of inoculation of yeast andfermentation temperature. The optimum conditions of fermentation had been studiedvia response surface methodology (RSM). According to the experimental results: theamount of inoculation of yeast was8.1‰(w/w), the optimum temperature was33.1℃, the time of fermentation was66h. Comparing the filtrate fermentation with thefermentation by the saccharified liquor, the result was founded that the content ofethanol by filtrate fermentation was higher than that by the saccharified liquor. Thisresult showed that filtrate fermentation had a certain development potential.Two fermentation experiments of15L bioreactor had demonstrated that themaximum content of ethanol was15.6%(v/v) with residue deoxidize sugar below0.35%and residue total sugar below0.5%under the condition of33.1℃fermented for66h. The experiments were repeated twice. According to theexperimental results, the significant difference was not founded. The result showedthat the experiment had a good repeatability.