An environment friendly and efficient process for xylitol bioconversion from enzymatic corncob hydrolysate by adapted Candida tropicalis

This study reported an environment friendly process for xylitol bioconversion from corncob hemicellulose hydrolysate prepared through xylanolytic enzymes by adapted Candida tropicalis. In order to improve the production of xylanolytic enzymes from Aspergillus terreus, the fermentation medium and growth conditions were optimized. Maximum xylanase (722 U/g) and beta-xylosidase (196 U/g) production were exhibited on wheat bran and corncob (mass ratio of 7:3) medium supplemented with 2% (v/v) NaNO3 and 0.05% (v/v) Tween 80 at pH 6.8, 1:1 (v/w) moisture level, 20% inoculum level and 30 degrees C for 120 h of cultivation. For preparation of corncob hemicellulose hydrolysate, the optimum enzymatic hydrolysis conditions contained enzyme dosage (30.6 U/g), water addition (19.2 mL/g), temperature (48.01 degrees C), pH (5.75). Under these conditions, the sugars of 18.03 g/L xylose and 4.87 g/L glucose were obtained in 8 h. The corncob hemicellulose hydrolysate was used for xylitol fermentation and the maximum xylitol yield of 75.14% was obtained by adapted C tropicalis after the optimization of fermentation. (C) 2014 Elsevier B.V. All rights reserved.