Production Of Ethanol From Biomass Fermentation Process In Series Integrated With Membrane Separation

The technology of ethanol, continuous fermentation combined with a silicone rubber membrane pervaporation has great importance in developing economized 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 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-bed columns 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:The composite PDMS membrane used in this study illustrated stable ethanol flux and selectivity in the pervaporation of aqueous ethanol solution (model solution) and fermentation broth. The ethanol fluxes increased with feed concentration of ethanol but the selectivity decreased slightly. The overall transfer coefficient of ethanol for model solution changed little under various feeding concentrations as long as temperature and the flow rate were constant.Effect of nitrogen source on growth of P. tannophilus: The growth and fermentation with carbamide as a sole nitrogen source were as good as those with peptone as a sole source.Effect of pH value and temperature for sugar fermentation by P. tannophilus: Theoptimum pH value range and temperature of growth were 35℃and 4.5-5.Influence of sugar concentration of glucose/xylose on fermentation: The mixture with a glucose/xylose ratio of 2:1 was used for all experiments. When substrate concentration increased, the residual sugar concentration of effluent in the reactor went up, and the ethanol concentration was slightly increased.Effect of combined PDMS membrane on the fermentation: Under the same conditions, the fermentation combined with membrane not only promoted the fermentation process but also enhanced the ethanol productivity. The elimination of these inhibited compounds from the system allows the increase in the productivity and rate of conversion of sugar to ethanol.