Screening Of High Butanol-producing Bacteria And Fermentation Of Butanol

Butanol, as a new generation of biofuels, has become the hot spot of the biofuel reseach in the world. Production of butanol from renewable feedstocks has been drawn attention to many countries. However, the cost of producing biobutanol remains significantly higher than the cost of petro-chemical derived butanol. In order to reduce costs in butanol production, the studies should be conducted as the following:breeding new strains with high butanol yield, developing new processes with high butanol productivity and lower energy intensity, using low-cost non-grain feedstocks.The study is to obtain mutated strains of high butanol productivity; optimization of butanol production medium and fermentation conditions; fermentation of poplar fiber hydrolysate. The main results are as follows:(1)Clostridium beijerinckii ATCC 55025 was mutated by UV with the purpose of increasing the yield of butanol. The results showed that mutant U-57 was obtained with high yield and hereditary stability in the conditions of UV 100 s. The yield of butanol and total solvent produced by mutant U-57 were 6.44 g/L and 10.57 g/L, which were 7.15% and 6.98% higher than the original strain. Hereditary stability test demonstrated that the productivities of mutant U-57 from the 1st to 7th serial passage were stable.(2)By Plackett-Burman, Box-Behnken and of experiment, the fermentation conditions of mutant U-57 were optimized. The result showed that the optimun fermentation medium were as followed:glucose 53.66 g/L, yeast extract 1.5 g/L, ammonium acetate 3.82 g/L, KH2PO40.75 g/L, MgSO40.2 g/L, FeSO4·7H2O 20 mg/L, MnSO410 mg/L, CaCO3 2.60 g/L, L-cysteine hydrochloride 0.5 g/L, p-aminobenzoic acid 3mg/L, vitamin B1 2 mg/L. By orthogonaldesign of experiment, the optimun fermentation conditions were as followed:fermetation temperature 37?, initial pH 6.5, inoculums volume 6%, liquid volume 85%. Under those conditions, the yield of butanol and total solvent produced by mutant U-57 were 7.85 g/L and 12.88 g/L, which were 21.9% and 15.3% higher than before.(3) Steam blasting of poplar was hydrolyzed by cellulase, the better hydrolysis conditions were as followed:temperature 50?, pH 5.5, time 45 h. And fermented by muntat U-57,the yeild of butanol was 2.19 g/L. The steam blasting of poplar also was use for SSF, By orthogonaldesign of experiment, the optimun fermentation conditions of SSF were as followed:fermetation temperature 40?, initial pH 5.9, inoculums volume 4%. Under those conditions, the yield of butanol and total solvent produced by mutant U-57 were 2.16 g/L and 3.44 g/L, which were 20.7% and 16.7% higher than before, that provided some references for subsequent fermentation medium optimization and enlarge experiment.