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Contribution to the performance improvement of the industrial process for obtaining ethanol from sugarcane by using microwave and ultrasonic energies


The present study consists of searching techniques to improve the productive capacity of the ethanol industry, by developing new technologies based on the application of microwaves and ultrasound, envisaging a better performance during the fermentative process. In order to achieve that target, one of the main objectives is to pasteurize the sugarcane must before fermentation. The must is composed by the mixture of the sugarcane juice and the syrup coming from milling the cane and from the sugar manufacturing, respectively. Such a must carries a heavy microbiological load made up of bacteria and wild yeasts. The presence of bacteria into the fermentation vats is associated to the decreasing of the fermentation performance, because part of the substrate is wasted to make others products like acetic and lactic acids, thus decaying the quality of the ethanol. Besides, bacteria may induce the occurrence of ferment flocculation, bringing a series of drawbacks to the process, such as yield reduction, expenditures with additives and bactericides, decrease of productivity, among others. On the other hand, wild yeasts are mostly flocculants by its nature, exhibiting low ethanol productivity and high multiplication rate. The industrial ferments utilized in most of the Brazilian sugar mills, selected in conformity to their excellent fermentation potential at the beginning of the harvest season, are rapidly substituted by the wild yeasts, changing the process performance. Pasteurizing by microwaves is an efficient and rapid method, easily adaptable to the present ethanol plants, where the majority of equipment operations are based on batch processes. In order to aggregate efficiency to the fermentation process after microwave pre-pasteurization, it is suggested applying ultrasonic energy: a few research works have already shown that its ministration under controlled conditions can accelerate the metabolism of Saccharomyces cerevisiae, among other capabilities, although this kind of energy for stimulating fermentation has not found any industrial scale application yet. The combination of the two technologies could be offering significant contribution to improve the ethanol production. Besides developing new technologies for the sugar-alcohol industrial sector, employing microwave and sonic energies signifies to take advantage of clean energies that can be obtained by co-generation from the surplus energetic sources of the sugarcane mills. (AU)

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