Research On The Optimize And Metabolic Flux Analysis Of Itaconic Acid By Fermentation From Wheat Bran Hydrolysate

Itaconic acid, as an important organic acid, is widely used in the field of chemical industry, medicine and agriculture. At present, itaconic acid is mainly produced by chemical synthesis with petrochemical raw materials. While with the depletion of the petroleum supply, utilizing green and safe biological conversion to prepare organic acid will become inevitable. In this work, dilute acid hydrolysis was applied to prepare wheat bran hydrolysate. We produced itaconic acid with Aspergillus terreus utilizing wheat bran hydro lysate. That is an effective way to improve its utilization and addition value.Use UV radation and metabolic regulation to improve the yield of itaconic acid.In this study, in order to further enhance the itaconic productivity by optimized the dilute acid hydrolysis, the detoxification parameters and the medium composition using single factor experiment and response surface methodology. The strain’s metabolic pathway and its relevant enzymes were investigated for metabolic flux analysis. Ultraviolet ray was used as mutagenesis source for the breeding of the strain. Then the change of products, enzymes and metabolic flux were analied for the mutation breeding strain.The main research results were as follows.(1) The optimal conditions by dilute acid hydrolysis were concentration of substrate 0.14 g/mL, acid concentration 3%, reaction temperature 108 ℃, reaction time 82 min. The Detoxification parameters were additive amount 6%, detoxification time 90 min, temperature 60 ℃. Under this condition, the removal rate of furfural was 91.5% and the hydrolysate concentration reached 43.24±0.51 g/L.(2) On the basis of single factor experiment, the optimal medium components were as follows:the biomass hydrolyte, NH4NO3, MgSO4, FeSO4, K2HPO4 and ZnSO4 were 100 g/L (including glucose 40 g/L and xylose 60 g/L),3 g/L,3 g/L, 0.16 g/L,0.2 g/L, and 0.15 g/L, respectively. The reasonable fermentation conditions were fermentation temperature 32 ℃, initial pH 2.5, rotation rate 200 r/min, fermentation period 96 to 120 hours, leading to the 39.14±0.43 g/L yield of itaconic acid.(3) The parental strain’s metabolic pathway and its relevant enzymes were investigated for metabolic flux analysis. Comparison with parent strain, the itaconic acid output of mutant strain raised 33.4%, the yield of citric acid reduced 75.8%. The aconitate decarboxylase and glucose-6-phosphate dehydrogenase of mutant strain raised 40.73%and 33.44%, respectively. The changes of related metabolic flux (F3, F11 and F50) were similar with them.(4) Stirred tank was employed to improve the experimental process. The optimum fermentation conditions were obtained by single factor experiment:spore suspension incubated for 24 h, rotation rate of 400 r/min, stirrer tank ventilation of 0.4 L/(L·min) and fermentation period of 96 hours. In this experiment, the yield of itaconic acid was 49.65 g/L±0.38 g/L.Breeding for this strain enhanced its itaconic-acid-productivity. The ability of producing itaconic acid from wheat bran hydrolysate and the advantages of fermentation process make this strain worthy of deep industrial development.