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 nu(max) values of 8.6 and 3.6g/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.