Processo fermentativo para produção de etanol utilizando glicerol bruto como substrato

Abstract

The aim of this work was to investigate the use of glycerol from biodiesel industry (raw glycerol) as a substrate in fermentation assays for production of ethanol. The assays were performed in shaker with agitation of 200 rpm, at temperatures of 30 and 37 °C, respectively for the microorganisms Saccharomyces sp. 1238 and 224 Escherichia coli ATCC 25922. In experiments with yeast Saccharomyces sp., it was varied concentrations of glycerol from fermentation medium at 0.5, 1.0 and 5.0 % v/v and the inoculum was set to 1% w/v. It was observed that the microorganism Saccharomyces sp. could not use glycerol as carbon source for ethanol production, but in assays using glucose, this substrate was rapidly consumed by the microorganism achieving an ethanol production of 5.5 g/L. It was varied the concentration of glycerol added to the fermentation medium: 1, 10, 15 and 20 g/L when Escherichia coli was used. By analyzing the influence of substrate concentration in fermentations, it can be concluded that the best condition for ethanol production, with this microorganism, was initial concentration of glycerol of 10 g/L. The consumption of glycerol by Escherichia coli was affected by the change of substrate concentration. It was observed that ethanol was produced after 8 h of fermentation with both raw and PA glycerol at 10, 15 and 20 g/L. It also observed the formation of acetic acid in the first hours of fermentation. The production of acetic acid was low, reaching a concentration of 0.15 g/L in fermentation using 10 g/L of raw glycerol. Analyzing the two microorganisms studied, it was found that only 224 bacteria Escherichia coli ATCC 25922 was adequate to the aim of this research, since the yeast was not produced ethanol in significant amounts.