Monday, May 5, 2008
6-25

Enzyme Pools for Sugar Cane Bagasse Hydrolysis

Leda M. F. Gottschalk, Raul A. Oliveira, Rodrigo R.O. Barros, and Elba P. S. Bon. Chemistry Institute, Federal University of Rio de Janeiro, Cidade Universitária, CT, Bloco A, sala 539, Ilha do Fundão, Rio de Janeiro, Brazil

Complete biomass hydrolysis to sugars of six and five carbons is carried out by cellulolytic enzymes (endoglucanases and exoglucanases) and β-glucosidase plus a collection of enzymes that are able to hydrolyze xylan, pectin and the linkages between the biomass polysaccharide moiety and lignin (auxiliary enzyme activities). The collective action of the auxiliary activities acts synergistically to facilitate the hydrolysis of cellulose.   In this work enzyme mixtures produced by Trichoderma reesei RUT C30 and a selected strain of Aspergillus awamori were assessed for their efficiency to hydrolyze untreated and treated sugar cane bagasse that is a potential raw material for biomass ethanol production in Brazil.  The crude enzyme preparations (culture supernatants) were individually concentrated using ultrafiltration and blended to obtain preparations with different profiles of cellulases and auxiliary enzymes. The blends were used to hydrolyze untreated and steam-explosion treated sugar cane bagasse. Experiments were performed at 40, 45 and 50°C. For comparison, the efficiency of the enzyme pools was evaluated “vis-a-vis” to the results that were obtained using commercial enzyme preparations. In all cases it was used a load of 10 FPU per gram of dry biomass. All enzymatic preparations were stable during the 72 hours of the hydrolysis experiments. A selected enzyme blend was as effective as the commercial enzyme preparations that were evaluated.  Preliminary results show that a biomass syrup presenting glucose 100 g/L was fermented to ethanol, with high efficiency, by the yeasts Saccharomyces cerevisiae.

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