(490f) Converting Lignocellulosic Biomass to Butanol By Clostridium

The crisis of crude oil supply and its negative impact on the environment make it essential to find renewable environmental friendly energy sources.  Butanol is one of the promising candidates due to its energy content comparable to gasoline.  However, several challenges limit the economic viability of biobutanol production from acetone-butanol-ethanol (ABE) fermentation, among which the cost of raw material can be up to 70% of the total production cost.  To make ABE fermentation more competitive, it is crucial to find an inexpensive and abundant feedstock, such as lignocelluloses.  Xylan represents the second most abundant polysaccharide in lignocellulosic biomass.  Thus far, few studies have been successful in directly converting xylan to biobutanol without prior enzymatic hydrolysis.  In this study, a wild-type Clostridium species strain G117 was used to produce butanol from different substrates.  Without enzymatic hydrolysis, 0.7g/L butanol was directly produced from xylan (60g/L) by strain G117.  Moreover, different from previous studies reporting ABE production, this study showed that only butanol was produced from xylan.  In addition to producing butanol from xylan and monosaccharides, strain G117 was also capable of producing 3.34g/L butanol from 17g/L xylo-oligosaccharides and 7.67g/L butanol from 31.6g/L cellubiose.  In comparison, after hydrolysis of xylan by xylanase and β-xylosidase simultaneously, strain G117 produced slighly higher biosolvents.  The results confirmed that the synergism of multi-enzymes (e.g., xylanase and β-xylosidase) on hydrolysis of hemicellulosic materials can enhance solventogenic Clostridium species to produce more biosolvents, but at a higher costs.  In summary, producing butanol directly from xylan is promising in converting sustainable feedstocks to biofuels.