ANÁLISE DA INFLUÊNCIA DA ADIÇÃO DE NUTRIENTES AO MOSTO DE MELAÇO DE CANA-DE-AÇÚCAR SOBRE O RENDIMENTO DE ETANOL

Abstract

The search for fuels from renewable sources that are sustainable and efficient has increased over the years. When observing the historical process of ethanol production, it is necessary to highlight its importance as a fuel - considered the clean and future fuel. Brazil is the pioneer country in the development of technology for the production of this biofuel and is currently the second largest producer in the world. In the case of Brazil, the main raw materials used to obtain ethanol, sugarcane juice and molasses. Molasses is a by-product of sugar production, in its composition it has an abundance of sugars, sometimes supplementation is necessary, especially with nitrogen and phosphorus salts. The present work aims to evaluate the influence of nutrients based on nitrogen (NH4)2SO4 and phosphorus (KH2PO4) on the ethanol yield obtained from fermentation, using sugarcane molasses as must. Before the fermentation process itself, a step was taken to treat molasses and prepare the inoculum, corresponding to 10% of the total volume of must. The inoculum was subjected to 30 ºC and 200 rpm. Five fermentative tests were carried out, all in duplicate, in Erlenmeyer flasks with a final volume of must of 150 mL, at a temperature of 30 ºC, pH 4.5, shaking at 100 rpm, in a shaker incubator (LUCCA 223), using 10% inoculum (%m/v), the fermenting agent being the yeast Saccharomyces cerevisiae (Safale US-05). The end of the fermentation was determined when the ºBrix remained constant after three consecutive readings. The process ended after 22 hours of fermentation. The alcoholic levels of experiments 1 to 5, were between 6.05 - 6.40 ° GL. The yield of ethanol from sugars ranged from 0.17 to 0.20 gethanol/ gglucose, the highest yield being obtained when the nutrient KH2PO4 was used at a concentration of 0.34 g/L. The addition of (NH4)2SO4 and the combined addition (NH4)2SO4 and KH2PO4, had virtually no effect on ethanol yield, when compared to wort without added nutrients. The fermentation efficiency (ratio between practical and maximum theoretical yield) varied between 33.42 and 39.31%.