Tuesday, April 20, 2010
8-71

Ball milling and wet disk milling pretreatments of sugarcane bagasse and straw for enzymatic hydrolysis and ethanol fermentation

Ayla Santana Silva1, Hiroyuki Inoue2, Shinichi Yano2, and Elba P. S. Bon1. (1) Biochemistry - Chemistry Institute, Federal University of Rio de Janeiro, Instituto de Quimica, sala 539 - Cidade Universitaria, Ilha do Fundao, Rio de Janeiro, Brazil, (2) Biomass Technology Research Center, National Institute of Advanced Industrial Science and Technology, 2-2-2 Hiro-suehiro, Kure, Japan

Currently, ethanol is produced, mainly, from sugarcane juice in Brazil and from corn in the USA. However, it is well established that the widespread use of ethanol will require technology based on lignocellulose biomass. Sugarcane bagasse and straw have been attracting the attention in Brazil as potential sources for lignocellulosic ethanol production. In this work, ball milling (BM) and wet disk milling (WDM) were compared regarding their effectiveness to treat sugarcane bagasse and straw. Pretreated materials were characterized by wide angle x-ray diffraction analysis, particle size distribution and scanning electron microscopy. The effectiveness of pretreatments was evaluated by enzymatic hydrolysis using a blend of Acremonium cellulase and Optimash BG. The resulting sugar syrups were used for ethanol fermentation. Glucose and xylose hydrolysis yields at optimum conditions for BM treated bagasse and straw were 78.7% and 72.1% and 77.6% and 56.8%, respectively. Milling times longer than 60 min for bagasse and 90 min for straw did not significantly improve sugar yields. Maximum glucose and xylose yields for bagasse and straw using WDM were 49.3% and 36.7% and 68.0% and 44.9%, respectively. BM improved the enzymatic hydrolysis by decreasing the crystallinity, while the defibrillation effect observed for WDM samples seems to have favored enzymatic conversion. Bagasse and straw BM hydrolysates were fermented by Saccharomyces cerevisiae strains. Ethanol yields from total fermentable sugars using a C6-fermenting strain reached 89.8% and 91.8% for bagasse and straw hydrolysates, respectively, and 82% and 78% when using a C6/C5 fermenting strain.

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