Optimize Medium Components For High Butanol Production Of One Clostridium Acetobutylicum Strain

Acetone - butanol fermentation has a long history, was once second only to alcohol fermentation of the world's second largest fermentation process. However , since the 1960',70' , because of the faster develope of Petrochemical industry, Acetone-butanol fermentation has declined continuously. Currently due to the exhaustion of natural gas and oil resources, Acetone-butanol fermentation is becoming more and more attractive for producing liquid fuels (butanol) and industrial raw materials.However, butanol has deeper toxicity during fermentation process. Growth of cell be stoped when butanol concentration reach or over 11 g/L, it leads to leakage of ions , with excessive ion leakage the cell cannot maintain its transmembrane ion gradients by ion pumping, at last the integrity of cell membrane phospholipid bilayer disappears and cell die. So production efficiency is low, makes acetone-butanol fermentation uneconomical and hard to popularize.In this paper, Clostridium acetobutylicum 8012 (from China Center of Industrial Culture Collection) 8012 was selected. With a view through experiment to optimizing butanol production exceeding 11 g/L.First, (NH₄)₂SO₄,CaCO₃,K₂HPO₄·3H₂O,KH₂PO₄,MgSO₄·7H₂O,FeSO₄·7H₂O, chloramphenicol was added at different concentration in order to study that if these factors were able to increase butonol production. And the result showed that butonol concentration was increased from 7.44 g/L to 10.33 g/L.Based on the single factor experiments, two level factorial design of Plackett-Burman was used to evaluate the most influencing factors. The result showed that two factors played the important role, it was MgSO₄·7H₂O and chloramphenicol. Then the path of Steepest Ascent was used to approach the optimal region. At last the concentrations of those two main factors were further optimized by using Central Composite and Response Surface Analysis. The optimal concentrations of the variables were determined as: Corn flour 70 g/L,(NH₄)₂SO₄3g/L,CaCO₃6g/L,K₂HPO₄·3H₂O 1.25g/L,KH₂PO₄ 1.5g/L MgSO₄·7H₂O0.43g/L, FeSO₄·7H₂O 0.015g/L, Chloramphenicol 0.137g/L. Final butanol concentration was 11.5 g/L, increased by 54% than the original production, solvent rate also increased form 65% to 72%. This experiment also shows that using this optimization method can effectively increase the butanol yield.