Dark fermentative hydrogen production from enzymatic hydrolysate of xylan and pretreated rice straw by Clostridium butyricum CGS5

Xylan and rice straw were used to produce H-2 via a two-stage approach combining feedstock pretreatment/hydrolysis and dark H-2 fermentation. Acinetobacter junii F6-02 was used to produce cellulolytic enzymes (mainly xylanase) to hydrolyze xylan and pretreated rice straw. The hydrolysates were converted to H-2 by Clostridium butyricum CGS5 via dark fermentation. Investigation of kinetics of xylanase on xylan and NaOH-pretreated rice straw shows v(max) values of 8.6 and 3.6 g/L/h, and K-m values of 10.6 and 26.9 g/L, respectively. A maximum hydrogen production rate of 62.5 and 26.8 ml/h/L was obtained from hydrolysate of xylan and pretreated rice straw, respectively, while the hydrogen yield was 0.70 and 0.76 mol H-2/mol xylose, respectively. Simultaneous saccharification and BioH(2) fermentation from xylan was also conducted but giving a lower hydrogen production rate (35.3 ml/h/L) than that of the two-stage process. (C) 2010 Elsevier Ltd. All rights reserved.