Tuesday, April 20, 2010
10-34

Evaluation of the digestibility of sugarcane bagasse clones with different lignin contents

Daniela B. Gurpilhares1, Walter Carvalho1, André Ferraz1, Marcio H. P. Barbosa2, and Adriane M. F. Milagres1. (1) Departamento de Biotecnologia, Escola de Engenharia de Lorena - USP, Estrada Municipal do Campinho, s/ n, Lorena, Brazil, (2) Departamento de Fitotecnia, Universidade Federal de Viçosa, Centro, Viçosa, Brazil

Several technologies for the pretreatment and disruption of lignocellulose structure have been developed, although these methods are often quite harsh and result in the degradation and loss of substantial parts of the lignocellulose substrate.  Unfortunately, the presence of lignin in plant cell walls hinders the breakdown of polysaccharides. The present work evaluates 10 contrasting sugar cane genotypes with high or low lignin contents. Current breeding program provide sugar cane lines with lignin content around 18% compared to 25% in control plants. These plants were directly hydrolyzed by an enzymatic cocktail composed of cellulases (20 FPU/g) and β-glucosidases (40 U/g) in sodium acetate buffer (50 mM, pH 4.8) for 72 h, 45 oC at 120 rpm. After this treatment, the enzymes were deactivated by boiling for 5 min and the supernatant was examined for sugars by HPLC. Enzymatic hydrolysis of the entire sugarcane bagasse resulted in the hydrolysis of 24.8% and 33.1% of the original cellulose in the high and low lignin sugarcane bagasse, respectively. To improve enzyme digestibility of the bagasses, experiments were conducted with the same samples pretreated with 2% (w/w) sulfuric acid at 150 oC during 30 min using batch reactors to determine how the effect of pretreatment affects rate and extent of hydrolysis. The acid pretreatment removed mainly hemicellulose and allowed more cellulase-cellulose interaction. The hydrolysis of residual cellulose has improved owing to the pretreatment and currently we are involved on determine pretreated biomass that contains varied amounts of cellulose, hemicelluloses and lignin obtained after enzymatic hydrolysis.

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