Monday, May 5, 2008
6-13

Cellulignin Hydrolysis Using Immobilized Cellulases

Wellington Sabino Adriano, Rafael Elias Martins, Dasciana Sousa Rodrigues, Roberto Campos Giordano, and Raquel Lima Camargo Giordano. Chemical Engineering Department, Universidade Federal de São Carlos, Washington Luiz, Km 235, Monjolinho, São Carlos, SP, Brazil

Celluclast was covalently immobilized in a chitosan-alginate hybrid gel, after activation of the support with glycidol and/or glutaraldehyde. The best enzyme derivative showed half-life ten-fold higher than the soluble enzyme, with recovered activity of 20%. Temperature and pH for maximum enzyme activity were 55°C and 4.5, for soluble Celluclast, and 65°C and 3.5 for the immobilized enzyme. The maximum enzyme load was 68 FPU/gsupport. A derivative containing 14.7 FPU/g support was used to catalyze the hydrolysis of sugar cane bagasse, previously submitted to alkaline treatment with sodium hydroxide. The performances of immobilized and soluble enzyme in the hydrolysis of 8.8% m/m of cellulignin, at 50°C, were compared. The total reducing sugar concentration reached with soluble Celluclast was much lower than with the enzyme derivative, for soluble enzyme concentrations in the reactor equal or higher than the apparent immobilized one. The feasibility of the reuse of the immobilized enzyme was verified by running a set of three repeated batches. Immobilized enzyme,  together with 5 FPU/gsolid of free enzyme, was used to hydrolyze 10% m/m of cellulignin. Each run was performed at 47°C for twelve hours, and at 37°C for 18 hours. After these reaction times, the solid was separated and returned to the reactor, being added more 5 FPU/g cellulignin of soluble enzyme and the same initial amount of cellulignin. The performance of the system was excellent, indicating that enzyme immobilization may be a good alternative to reduce costs of ethanol production from lignocellulosic materials.

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