Tuesday, April 20, 2010
10-26

Application of immobilized cellulases on the hydrolysis of steam exploded sugarcane bagasse after alkaline pre-treatment

Rafael E. Martins1, Dasciana S. Rodrigues1, Mirella L. Carvalho1, Wellington S. Adriano2, Raquel L. C. Giordano1, and Roberto C. Giordano1. (1) Chemical Engineering Department, Federal University of Sao Carlos, c.p. 676, Sao Carlos, Brazil, (2) Chemical Engineering, Federal University of Ceara

Sugar cane bagasse is a lignocellulosic material available in Brazil to be used as raw material in the ethanol production. However, before fermentation, this material requires some pretreatment process to reduce substrate recalcitrance. Although the hydrolysis via chemical route is cheaper, the enzymatic hydrolysis of cellulose is being considered more viable, since it avoids the generation of fermentation inhibitors that occurs in the former route. Reduction of the amount discarded enzymes after the hydrolysis process may be important to make economically feasible the production of ethanol from lignocellulosic materials. Immobilization and stabilization of the enzymes allow their reuse in the process and therefore may reduce the enzyme costs for cellulose hydrolysis. This work shows results obtained in the cellulignin hydrolysis catalyzed by two commercial cellulases complexes, soluble and immobilized using two approaches. Celluclast and Acellerase were immobilized on an chitosan-alginate support activated by glutaraldehyde or encapsulated in chitosan and crosslinked with glutaraldehyde. The second method led to more stable enzyme derivatives, which showed to be 33 times more stable than the dialyzed soluble enzyme. Results of the cellulign hydrolysis at 50°C, pH 4.8 by soluble and immobilized enzymes showed higher conversions for the immobilized ones, due to the inactivation of the soluble cellulases. Adsorption assays showed that part of the immobilized enzymes was not covalently immobilized and desorbed during the hydrolysis assays, what explained the initial action of the endocellulases when using immobilized enzymes. Based on these results, sequential assays using both free and immobilized cellulases were run.

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