Monday, April 19, 2010
3-40

Bioethanol production from steam-exploded barley straw

María del Prado García-Aparicio, J.M. Oliva, Paloma Manzanares, Mercedes Ballesteros, Felicia Sáez, and M.J. Negro. Renewable Energies Department, CIEMAT, Avda. Complutense, 22, Madrid, Spain

In this work, the effect of substrate loading [washed water insoluble solids (WIS) from steam-pretreated barley straw] on different enzymatic-based process configurations was assessed in order to obtain the highest ethanol yield. Steam explosion pretreatment conditions, selected in a previous work, were 210 ºC for 5 minutes. Firstly, different substrate loading (2-15%, w/v) were studied during enzymatic hydrolysis tests at 50 ºC for 120 hours. The effects of xylanase addition on glucose production and cellulose conversion at different substrate loading were also investigated. In addition, three different process configurations, including separate hydrolysis and fermentation (SHF), simultaneous saccharification and fermentation (SSF) and presaccharification and simultaneous saccharification (PSSF), were performed for 72 hours for ethanol production using the thermotolerant yeast Kluyveromyces marxianus CECT 10875. Secondly, the configurations above were compared at three WIS concentration (5, 10 and 15%), and previously washed with distilled water to remove degradation products. The influence of xylanase addition on the ethanol yield was studied as well.

Results show that endoxylanases improved cellulose conversion and ethanol yield compared to the control enzymatic mixture, markedly at low substrate concentration. Regarding process configurations for the period of 72 hours, SSF with endoxylanases produced the best ethanol yields, 74.2 and 70% (% of theoretical) for 5 and 10% WIS respectively.



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