Monday, April 30, 2012
Napoleon Ballroom C-D, 3rd fl (Sheraton New Orleans)
Lignin depletion in new cultivars or transgenic plants has been identified as a way to diminish the recalcitrance of lignocellulosic materials. Direct enzymatic digestion of these materials give some discrimination concerning their digestibility, but usually the cellulose conversion to glucose is lower than 30% in the case of sugar cane bagasse. This work evaluates an alkaline pretreatment of eleven sugarcane hybrids and two reference samples as a method for enhancing the sample digestibility aiming a better discrimination among cultivars. The sample treatment with 1% NaOH solutions at 100 oC for 1 h resulted in the solubilization of approximately 32% of the material dry mass with small variation among samples. Conversely, the treatment with 0.1% NaOH solutions resulted in an average of 10% of dry mass solubilization, with significant variation among the samples. The mass balances for these treatments showed that the cellulose fraction remained almost unchanged whereas the hemicellulose decreased in the experimental hybrids and commercial cultivars. The lignin fraction remained almost unchanged in hybrid plants but decreased considerably in the commercial cultivars. Direct enzymatic hydrolysis of the studied materials by a mixture of commercial cellulases showed a cellulose conversion varying from 13% to 32% after 72 h of reaction. Alkali-treated samples provided enhanced cellulose conversion levels, varying from 23% to 52% at same reaction time. In general, the hybrids that lost mainly hemicellulose in the pretreatment provided a lower increase in the cellulose conversion levels as compared to the commercial cultivars that lost lignin in addition to hemicellulose.