| In recent decades, a large number of oil and other resource were exploitated and used by humans, so that the energy situation is increasingly grim, more and more serious environmental pollution and global warming appeared, new energy development is imminent. Biobutanol has some characteristics such as:the small causticity, the low saturated vapor pressure, and the similar energy density with gasoline, so it can be added into a gasoline engine directly without alteration. Wood fiber is a rich and large reserved resource in China, it can be used to produce butanol after hydrolysis. Therefore, Lignocellulosic material is an alternative to traditional food ingredients to avoid food crisis and reduce production costs.In this study, the Clostridium saccharobutylicum BAA-117was bought from the United States ATCC. The results showed that:the utilization of single sugar was that: Mixed sugar (glucose27.5g/L, arabinose3g/L, xylose19.5g/L)> glucose> xylose> arabinose;the enzymatic hydrolysate contained46.8g/L total reducing sugars, after72h of fermentation, the total ABE in the system was6.25g/L, of which butanol was4.73g/L,the ABE productivity was0.089g/(L.h).With medium fermentation,the yield of butanol and productivity of total ABE were6.9g/L and0.1323g/(L.h) respectively;After72h fermentation adding20g/L mixed sugar,the yield of butanol and productivity of total ABE were improved to be7.28g/L and0.1413g/(L.h). Consequently, the butanol product increased58.8%than single poplar fiber fermentation.Clostridium saccharobutylicum BAA-117was mutated by UV with the purpose of increasing the yield of butanol. The results showed that mutant A-18and A-19were obtained with high yield in the conditions of UV100s. The yield of butanol and total solvent produced by them were8.26g/L11.53g/L and7.73g/L10.52g/L, which were23.8%31.6%and15.9%20.1%higher than the original strain. Hereditary stability test demonstrated that the productivities of mutant A-18were stable from the1st to5th serial passage. By Plackett-Burman and the experiment of Box-Behnken, the fermentation conditions of mutant A-18were optimized. The optimun fermentation medium were followed:Mixed sugars50g/L (glucose27.5g/L, arabinose3g/L, xylose19.5g/L), Ammonium sulfate3.5g/L, MgSO4-7H2O0.4g/L, yeast extract1.8g/L, KH2PO40.62g/L, FeSO4-7H2O15mg/L, CaCO34.5g/L, L-cysteine hydrochloride0.7g/L. By orthogonaldesign of experiment, the optimun fermentation conditions were as followed:initial pH6.8, fermetation temperature36℃, liquid volume75%, inoculums volume9%. Under those conditions, the yield of total solvent and butanol produced by mutant A-18were12.82g/L and8.71g/L, which were11.2%and5.4%higher than before. |
