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Abstract
Since fossil fuels are nonrenewable energy sources, researchers are increasingly interested in utilizing fermented ethanol to substitute fossil fuels. Ethanol is not only a basic raw material in chemical industry, it is also used as a gasoline additive to increase its octane number. Recently, ethanol has become an important energy source while people are looking for an alternative energy source and also are serious about environmental protection concept. Although it cast more to produce ethanol using fermentation method than chemical synthesis, however, 80% of the world total beverage alcohol are produced using fermentation method. The main draw back of this method is that its production rate is slow and the concentration of the product is low. Nevertheless, it has it strong point, that is, it is made from a renewal resource so long as sunlight, air and water exist.
This study utilized the photosensitized immobilization method for entrapment of yeast cells in the cross-linked polymeric membrane. The immobilized yeast membrane was then used for ethanol production. This research lays emphasis on using continuous fermentation process to produce ethanol with high yield.
To carry out photosensitized polymerization experiment,1% of benzoin iospropyl ether (photosensitizer) and 0.167% of dry yeast cells were added to a mixture of polyethylene glycol diacrylate (PEG-Da) and 2-hydroxyethyl methacrylate (HEMA) at 10：90. After 15 sec of UV treatment on each side .The solidified membrane can be used for ethanol fermentation with relatively high yield.
Stability test on this membrane revealed that it can last for at least 45 days batch wisely. Using a continuous bio-reactor packed with 40 pieces of immobilized membrane and with a flow rate of 0.6 ml/min, the obtained ethanol has a concentration of 8.36 % which is lower than that obtained by batch fermentation. It may have been due to stagnant flow in the long column or due to microbial contamination.
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