Study On The Biological Transformation Of Acetic Acid To Mevalonic Acid And Its Downstream Products By DNTF

Mevalonic acid is thekey precursors of isopentenyl diphosphate(IPP)and dimethylallyl pyrophosphate(DMAPP)synthesized,andIPP and DMAPP after catalystto synthesize terpenoids,synthesis of isoprenedownstream productscan be used in the synthesis of isoprene rubber,lubricating oil additives,rubber vulcanization agent and catalyst function;t the mevalonate pathway to the synthesis of mevalonic acid and a variety of downstream products,for example,the artemisinin has special efficacy in the treatment of malaria,the greatly medicinal value of carotenoid,ect;as aviation fuel C10 and C15 platform compoundof bio based fuels.Therefore,the mevalonic acid and its downstream products' market prospect is very broad.This paper choose the commonly used microbial strains in fermentationindustrial –Escherichia coli.Escherichia coli as biological carrier,establish the substratewith acetic acid as the sole carbon source,synthesis system for the synthesis of mevalonic acid and downstream products.The mevalonate pathway has been constructed to study the optimization of experimental,using wastewater with acetic acid as the sole carbon source substrate for synthesis of mevalonate,by using single factor experimental analysis method to determine the optimal conditions for the synthesis of fermentation medium beef powder adding amount of 2g/L,the fermentation medium pH=7,induced by the temperature of 27?.Then the high density fermentation experiments were carried out in 5L fermentor to investigate the fermentation characteristics and kinetic characteristics of mevalonic acid and the downstream productionsby acetic acid wastewater.Cell mass,mevalonate and residual acetate concentration inthe fermentation were examined.Fermentation process parameters,as dissolved oxygen and solution pH values were also discussed.The dry cell weight,mevalonate concentration and yield were 1.5 g/L,3.83 g/L and 0.12 g/g,respectively.Growth producing and substrate consumption kinetics model of bacteria were described by three kinetic equations.The result showed that mevalonate synthesis was partial correlated with cell growth.Cell growth,mevalonate production and acetate consumption simulated very well with the kinetic models,which provides the theoretical foundation for further research and industrial application.On the basis of the study on the synthesis of acetic acid by recombinant Escherichia coli,the strains of acetic acid coproduction succinic acid and mevalonic acid were screened out and the efficientstrains were constructed.Through flask culture,succinic acid producing strain FHR-1 was screened,according to the metabolic pathway of the target product,through gene engineering method,overexpression of pyridine nucleotide transhydrogenase gene pntAB,andthe strain of acetic acid coproduction succinic acid and mevalonic acidsuccessfully constructed : E.coli BL21(DE3)/pYJM16-pntAB/p FHR-1,mevalonate conversion rate increased from 12% to 15%,succinic acid conversion rate increased from 23% to 32%,greatly improving the utilization rate of carbon atoms.Screening and optimization of conditions for synthesis of isoprene from acetic acid.The optimal strainE.coliBL21:: Trc-low/YJM16-ispSMJ/ FHR-1which synthesis of isoprene by acetic acid wasscreened out through shake flask;and to explore the optimal conditions of acetic acid as the carbon source offermentation of mevalonate and isoprene,the optimized conditions for beef powder adding amount of 2g/L,induced by a temperature of 27? and medium pH=7.The yield of isoprene was 4.33mg/L,and the yield of mevalonic acid was 423mg/L,which laid the foundation for the use of acetic acid as the carbon source for the synthesis of isoprene and terpenoid.