Ethanol Fermentation Process In Series With Gel Immobilized Cells And Integrated With Membrane

Novel technologies of continuous ethanol fermentation with mixed substrates consisting of glucose and xylose have great importance in developing economized non-grain agricultural product processing and new petroleum-replaced clean energy production.Lignocellulosic materials, which consist of cellulose, hemicellulose, and lignin as their main constituents, are the most abundant renewable organic resources on the earth at present. The production of fuel alcohol using the inexpensive and renewable sugar of biomass is one of the most effective methods to resolve energy crisis in the world. The method of continuous ethanol fermentation with mixed substrates consisting of glucose and xylose in two series-wound fixed columns packed with gel beads of immobilized cells was applied in this experiment. The polydimethylsiloxane (PDMS) membranes were used for the separation of volatile compounds from the broth. The removal of these inhibitive compounds allows the increase in the productivity and the rate of conversion of sugar to ethanol.The major experimental results are as follows:Effect of air input on the xylose fermentation by P. tannophilus: the optimum volume of air input per minute was 96-145ml/min for the xylose (25g/L) fermentation by P. tannophilus at the dilution rate of 0.382h^-1.Effect of glucose concentration on the xylose fermentation by P. tannophilus: when the glucose/xylose ratio reached 1:1 at 35℃, dilution rate of 0.382h^-1, the inhibition of glucose for the fermentation of xylose became obvious.Effect of dilution rate on the fermentation of the equipment without membrane: at the total reducing sugar concentration of 75g/L (glucose/xylose was 1:1), temperature of 35℃, air input of 120ml/min, pH4.5, the optimum dilution rate was 0.321h^-1.Effect of membrane on the production of ethanol under the optimum operation conditions: under the same conditions, the fermentation process combined with membrane was greatly promoted and the ethanol productivity was enhanced. The elimination of these inhibited compounds from the system allows the increase in the productivity and rate of conversion of sugar to ethanol.The optimum operational parameters of the system were determined with the factorial experiments.