Improvement of Enzymatic Hydrolysis of Steam-exploded Wheat Straw by Simultaneous Glucose and Xylose Liberation

M. Marcos, M. T. García-Cubero, G. González-Benito, M. Coca, S. Bolado and S. Lucas

Abstract
This work aimed at enhancing enzymatic hydrolysis of steam-exploded wheat-straw by investigating factors affecting hydrolysis. A multi-objective optimization of glucose and xylose release was performed using Celluclast 1.5L and Ultraflo-L mixtures with maximal values of 20 for enzyme/substrate ratio, 72 h for reaction time, 50 °C for temperature and 5.0 for pH. The highest sugar yields obtained were 18.9 ± 0.4 g/100gDM for glucose and 4.7 ± 0.2 g/100gDM for xylose. The addition of Ultraflo-L could increase the liberation of xylose, but has no pronounced effect on glucose release. The effect of β-glucosidase addition to the Ultraflo+Celluclast mixture for improving sugar yield was also studied. The β-glucosidase supplementation increased the production by approximately 29.9 % for glucose and 5.9 % for xylose, when a β-glucosidase loading of 10 % gβ-glucosidase/gcellulose was used.

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Keywords
enzymatic hydrolysis, cellulase, β-glucosidase, RSM, multiobjective optimization