Optimization of β-Glucosidase, β-Xylosidase and Xylanase Production by Colletotrichum graminicola under Solid-State Fermentation and Application in Raw Sugarcane Trash Saccharification

Efficient, low-cost enzymatic hydrolysis of lignocellulosic residues is essential for cost-effective production of bioethanol. The production of beta-glucosidase, beta-xylosidase and xylanase by Colletotrichum graminicola was optimized using Response Surface Methodology (RSM). Maximal production occurred in wheat bran. Sugarcane trash, peanut hulls and corncob enhanced beta-glucosidase, beta-xylosidase and xylanase production, respectively. Maximal levels after optimization reached 159.3 +/- 12.7 U g(-1), 128.1 +/- 6.4 U g(-1) and 378.1 +/- 23.3 U g(-1), respectively, but the enzymes were produced simultaneously at good levels under culture conditions optimized for each one of them. Optima of pH and temperature were 5.0 and 65 degrees C for the three enzymes, which maintained full activity for 72 h at 50 degrees C and for 120 min at 60 degrees C (beta-glucosidase) or 65 degrees C (beta-xylosidase and xylanase). Mixed with Trichoderma reesei cellulases, C. graminicola crude extract hydrolyzed raw sugarcane trash with glucose yield of 33.1% after 48 h, demonstrating good potential to compose efficient cocktails for lignocellulosic materials hydrolysis.