Effects Of Different Control Conditions On Metabolic Flux Distribution Of Serratia Marcescens

The metabolic network is a complex network structure in which the bacteria gene,enzyme and metabolic reactions correlate to each other through bioinformatics.Metabolic flow analysis(MFA)is based on the material balance principle,through the mathematical model to calculate the metabolic flux distribution of bacteria in the fermentation for understanding metabolic rule of the bacteria further.A lot of research found that the accumulation of metabolites is affected by inherited trait,environment alteration.Our laboratory found that dissolved oxygen condition and signal molecule had a great effect for 2,3-butanediol in Serratia marcescens at early stage experiment,as well between different species of serratia marcescens.Therefore In this article the effect of Serratia marcescens H32 metabolic flux distribution under different inherited trait,ventilation rate and Signaling molecule concentrations was mainly explored.The experimental results were as follows.1.The metabolic network of S.marcescens H32 reconstruction and the metabolic flux distribution under different ventilation rate conditionsIn this chapter the metabolic flux distribution of Serratia marcescens H32 under different aerobic conditions was explored,the results showed that 2,3-butanediol and butanedioic acid accumulation increased under 1.5 L/min aerobic condition.While the concertration and distribution of acetoin and ethonal increase under 0.8 L/min aerobic condition.Therefore,the ventilation rate increased appropriatly under low dissolved oxygen condition contribute to 2,3-butanediol and butanedioic acid formatoin,inhibited acetoin and ethonal accumulation.The ratio of NAD+/NADH was greater than 0.8 L/min and 2,3-butanediol dehydrogenase fumaric acid reductase activity increased,at the same time reduce the alcohol dehydrogenase activity.2.The metabolic difference analysis between S.marcescens MG1 and S.marcescens H32This chapter was mainly to know the difference of metabolic flux distribution between S.marcescens MG1 and S.marcescens H32.Significant difference of metabolism between S.marcescens MG1 and S.marcescens H32 during fermentation was found.The analysis of metabolic flux distribution of S.marcescens MG1 and S.marcescens H32 under same fermentation condition showed that the ethanol,acetoin,acetic acid,butanedioic acid concerntration and distribution of S.marcrescens H32 were all above of S.marcescens MG 1.Nevertheless,the accumulation of 2,3-butanediol and citric acid shows opposite result.The ratio of NAD+/NADH in S.marcescens H32 was significantly higher than S.marcescens MG1 during stationary phase,as alcohol dehydrogenase and fumaric acid reductase activity,while 2,3-butanediol dehydrogenase activity was significantly lower than the latter.So the determination of enzyme activity and reducing power results showed that the difference of metabolism between S.marcescens MG1 and S.marcescens H32 during fermentation was caused by the amount of 2,3-butanediol dehydrogenase and NADH availability.3.The effect of Signal molecule for metabolic flux distribution in S.marcescens H32This chapter analyzed the difference of the metabolic flux distribution between S.marcescens H32 and absence of signal molecules synthetase strain S.marcescens?swrI that our laboratory has constructed in the early stage by metabolic flux analysis.The results showed that the strain absence of Signal molecule synthetase gene inhibited the growth of bacteria,reduced the sugar consumption ability,improved the accumulation of ethanol,acetoin and organic acids as succinate,lactate,acetate,reduced the accumulation of 2,3-butanediol greatly.The results of enzyme activity determination showed that the strain absence of Signal molecule synthetase gene reduced the amount of 2,3-butanediol dehydrogenase,ethanol dehydrogenase and lactate dehydrogenase,improved the fumaric acid reductase.So the signal molecule mainly regulate of 2,3-butanediol leaded to the change of the whole metabolic flux distribution.Adding 10 ?M standard signal molecule C6-HLS into fermentation medium for fermentation,the enzyme activity and the accumulation of S.marcescens?swrI metabolites have been recovered modestly.4.The reconstruction of signal molecule synthetase gene over-experssion S.marcescens MG1/pBud-swrIIn the last chapter,signal molecules synthetase gene of S.marcescens MG1 was connected to pBud plasmid to form a recombinant vector and then inserted into the wild S.marcescens MG 1 by electroporation method.The signal molecules synthetase was markedly increased in the resultant over-expression bacteria.Analyzing the metabolic flux distribution of serratia marcescens under different conditions to know the effect of ventilation rate,signal molecule and inherited trait for metabolites and its main nodes of In order to provide scientific basis for serratia marcescens fermentation optimization and reconstruction.