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 H2 via a two-stage approach combining feedstock pretreatment/hydrolysis and dark H2 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 H2 by Clostridium butyricum CGS5 via dark fermentation. Investigation of kinetics of xylanase on xylan and NaOH-pretreated rice straw shows νmax values of 8.6 and 3.6 g/L/h, and Km 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 H2/mol xylose, respectively. Simultaneous saccharification and BioH2 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.