Portal de Conferências da FURB, III Semana da Pós-graduação em Química e XXIII Semana Acadêmica do curso de Química da FURB

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COMPARISON OF CELLULOSIC ETHANOL PRODUCTION FROM STEAM-EXPLODED Eucalyptus urograndis AND CANE BAGASSE AT HIGH TOTAL SOLIDS AND LOW ENZYME LOADINGS
Luana Marcele Chiarello, Priscila Vinholi Neves, Carlos E. Arnt Ramos, Luiz Pereira Ramos

Última alteração: 2018-08-24

Resumo


Cellulosic ethanol is one of the most important biotechnological products to mitigate the consumption of fossil fuels and to increase the use of renewable sources for fuels and chemicals. Performing the enzymatic hydrolysis step in high consistency using high total solids (TS) and relatively low enzyme loadings can offer significant advantages to the cellulosic ethanol production process. These advantages involve the reduction in capital cost for hydrolysis and distillation, particularly due to the fact that high sugar concentrations are produced in the substrate hydrolysate for fermentation. In this work, different steam-exploded materials were used for enzymatic hydrolysis at high total solids (TS) and low enzyme loadings and the fermentability of their corresponding hydrolysates was tested using an industrial strain of Saccharomyces cerevisiae. Pretreatment was carried out by autohydrolysis using Eucalyptus urograndis wood chips and sugarcane bagasse under conditions that were pre-optimized in earlier studies, 210 °C for 5 min and 195 °C for 7.5 min, respectively. Enzymatic hydrolyses were carried out in a Labfors 5 BioEtOH reactor (Infors-HT) during 72 h at 50 °C and 150 rpm, using 62.5 mg of Cellic CTec3/g  of dry substrate in 50 mol/L acetate buffer at pH 5.2. The reactor was fed with pretreated material by adding 5 wt% TS at every 1.5 h, reaching 20 wt%. Fermentation was carried out with 1 g L-1 of Thermossac Dry (Lallemand) at 35 °C during 20 h. Pretreatment by steam explosion resulted in high yields of enzymatic hydrolysis from both sugarcane bagasse and eucalypt chips, which were higher than 95 % after 72 h at high total solids and a relatively low enzyme loading. With regard to fermentation, both substrate hydrolysates were easily converted to ethanol, giving yields above 25 g L−1 and productivities of 2.3 g L−1 h−1 for eucalypt and 2.2 g L−1 h−1 for bagasse after only 12 h of fermentation. Glucose consumption was complete after 12 h, suggesting that the process can be interrupted at this time without any loss in process efficiency. However, the glucose yield was higher for eucalypt while steam-treated bagasse gave yields 25% lower. Under the conditions, when a projection of the results of pre-treatment, enzymatic hydrolysis and fermentation was carried out, it was concluded that the eucalyptus wood chips had a higher potential for the production of cellulosic ethanol than the sugarcane bagasse. Sugarcane bagasse glucans showed the potential to boost the ethanol production from sugarcane culms by 31 %, from the 80 L t−1of first generation to a total production of 105 L t−1. On the other hand, E. urograndis plantations are able to achieve cellulosic ethanol productivities of 2832.2 L ha−1 year−1, which was 57.8 % higher than the projected value of 1794.5 L ha−1 year−1 that was obtained for sugarcane bagasse.