Delignified Eucalyptus wood by glycerol-organosolv for second generation bioethanol production

Abstract

The bioethanol from lignocellulosic materials (LCMs) or 2nd generation bioethanol is a promising alternative to fossil fuels. The complex structure of LCMs complicates its fractionation, being the main obstacle for its use. Several treatments have been proposed for this purpose. Organosolv-delignification is used for lignin solubilization which is recovered by acidification. Besides this, this treatment also allows to increase the susceptibility of the pretreated solids to enzymatic hydrolysis. The crude glycerol is a by-product that is generated in the biodiesel industry and represents a 10 % of total biodiesel output. Consequently, the use of glycerol in organosolv process can be an interesting alternative in the fractionation of LCMs. In this work, the Eucalyptus wood was pretreated at 200 ºC during 67 min using glycerol-delignification process. The chemical composition of delignified solid was: glucan (77 %), xylan (5 %) and lignin (16 %) corresponding to 67 % of delignification, in respect to raw material. The solubilized lignin was precipitated with HCl (0.3 mol/L) and characterized by FTIR. The delignified solid was used as substrate in simultaneous saccharification and fermentation (SSF) process. The SSF was carried out using a thermotolerant flocculating Saccharomyces cerevisiae CA11 for ethanol production. The conditions of operation were: 10 % of substrate and 30 FPU/g of substrate of enzyme loading. The SSF experiment was performed at 42 ºC and 150 rpm achieving a maximum ethanol concentration of 40 g/L that corresponds an ethanol yield of 91 %.