The Influence And Mechanism Of Dissolved Oxygen On Bacillus Sp. C2 Acetone-butanol Fermentation

Strictly anaerobic fermentation condition is one of important limiting factors to butanol industrialization.In this study,butanol fermentation carried out in different dissolved oxygen condition by the bacillus sp.C2 which was screened by our lab in order to research the effection of different dissolved oxygen condition on bacillus sp.C2 butanol fermentation and build the fermentation kinetics model in facultative anaerobic and strictly anaerobic conditions.Revealed influence and mechanism of dissolved oxygen on bacillus sp.C2 acetone-butanol fermentation through analyzed,the concentration and ratio of intracellular key enmzye activities,ATP/ADP and NAD(P)H/NAD(P)+ in different dissolved oxygen condition.The results of butanol fermentation in shake flask showed: butanol and total solvent production reached 9.50 and 13.02 g/L in facultative anaerobic condition higher than 8.52 and11.74 g/L in strictly anaerobic condition by 11.5% and 9.01%,respectively.The results of butanol fermentation in 40 L fermenter showed: butanol and total solvent maximum production in facultative anaerobic and strictly anaerobic condition reached 11.395,16.758,10.136 and 14.822 g/L,respectively.The yield of butanol and solvent in facultative anaerobic is higher than strictly anaerobic 13.06% and 12.43%,respectively.The butanol fermentation kinetics model of cell growth,product synthesis and substance consuming in facultative anaerobic condition is (?),The butanol fermentation kinetics model of cell growth,product synthesis and substance consuming in strictly anaerobic condition is (?).The dates of the six key enzyme activities displayed: the maximum enzyme activity of alcohol dehydrogenase,butyl aldehyde dehydrogenase,butyl alcohol dehydrogenase,acetyl acetyl-co A transferase,acetate kinase and butyric acid kinase in facultative anaerobic is higher than in strictly anaerobic 55.4,22.6,72.9,72.8,9.4 and 11.9 %,respectively.Results of changes intracellular ADP/ATP concentration and ratio suggested the initial concentration of intracellular ADP and ATP in facultative anaerobic condition is higher than in strictly anaerobic condition 3.27 and 1.4 fmol/cell(mg)respectively,then the ATP level raised 8.89 and 6.00 fmol/cell(mg)and ADP level fell by 8.03 and 15.81 fmol/cell(mg)respectively in both conditions at 24 h.The ratio of ADP/ATP showed a trend of dynamic changes.Results of changes intracellular NAD+/NADH and NADP+/NADPH concentration and ratio in different d dissolved oxygen conditions suggested At fermentation 24 h,the NAD+ /NADH maximum concentration and the growth rate in facultative anaerobic and strictly anaerobic conditions reached 13.420 and10.949 ?M,0.350 and 0.449 ?M/min respectively.NADP+/NADPH maximum concentration and the growth rate reached 0.307 and 0.330?M,0.008 and 0.009?M /min respectively.After 24 h the NAD+/NADH and NADP+/NADPH concentration began to decline.In this paper,an effective facultative anaerobic fermentation process has been established through the optimization of fermentation parameters and control of dissolved oxygen concentration contribute to provide theoretical basis and technical support to bacillus sp.C2 butanol industrialized production in facultative anaerobic condition.