Direct fermentation of xylan by Clostridium strain BOH3 for the production of butanol and hydrogen using optimized culture medium

Clostridium strain BOH3 is able to utilize 10 g/l of xylan in reinforced clostridial medium (RCM) and produce butanol and hydrogen. However, increasing xylan concentration to 30 g/l does not enhance the production of butanol and hydrogen due to insufficient expression of xylanase enzyme (27.5 U/mg). To enhance the xylanase activity, an optimized culture medium (OCM), which consists of sugarcane bagasse hydrolysate (11.75 g/l), ammonium sulfate (8.92 g/l) and iron (III) chloride (1.45 mM) is designed. In the optimized OCM, Clostridium strain BOH3 expresses more xylanase and shows higher xylanase activity (44.05 +/- 0.25 U/mg) in the OCM. This activity is about 1.6-fold higher than that in the original RCM. Employing OCM as a medium, Clostridium strain BOH3 effectively ferments high concentration (30 and 50 g/l) of xylan and produces 12.05 +/- 0.15 and 14.80 +/- 0.15 g/l of butanol and 1.78 +/- 0.08 and 2.65 +/- 0.15 l/l of hydrogen, respectively. (C) 2013 Elsevier Ltd. All rights reserved.