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

Abstract

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. © 2013.