The Studies On L-threonine Fermentation Condition And Fermentation Kinetics

According to the theory of metabolic control fermentation and fermentation kinetics, the dissertation focuses on the fermentation condition and its fermentation kinetics of L-threonine producing strain FCD13. The main research contents and results are as follows:1) The batch fermentation condition of stain FCD13in shake flask was studied. Based on the above single-factor test, the fermentation medium was optimized by orthogonal design test and BP neural network simulation, and to identify the fermentations conditions. The formulation of the optimum fermentation medium(g/L) was sucrose60,(NH4)2SO423, KH2PO42.0, MgSO41.1, FeSO40.6, MnSO40.34, CaCO330. The optimum fermentation condition was obtained:the optimum initial pH was7.0, the optimum liquid volume were25mL culture in250mL shake flasks, the optimal amount of inoculation was4%, the rotation speed of240r/min and the fermentation temperature was37℃.2) Based on the above optimum shake flask fermentation condition, the L-threonine batch fermentation kinetics was studied by Matlab software according to the experimental data from shake flask fermentation. Three kinetic models were constructed which could be well reflect the cell growth, product formation and substrate consumption in the process of batch fermentation.3) Studied on The influence of the stirring speed, pH and temperature on the L-threonine fermentation and its kinetics was studied. Based on experimental research and results analysis, different kinetics phenomena under the different fermentation conditions, thus explaining the optimal conditions:the fermentation stirring speed was500r/min, pH was7.0and temperature was37℃.4) The influence of the amount of additives on the L-threonine fermentation was studied. The results showed that the optimal dosage of Biotin was40μg/L, the optimal dosage of thiamine was40μg/L and the optimal methionine was50μg/L.5) Fed-batch fermentation with FCD13in shake flask was studied. The optimum initial sucrose and (NH4)2SO4concentration. The effect of feeding nutrition on fed-batch fermentation in shake flask was also studied. Based on the fed-batch fermentation in shake flask and batch fermentation, fed-batch fermentation in5-liter fermentor was performed. The results showed that the production of L-threonine reached25.28g/L after fermentation for60hours.