Modeling and simulation of continuous production of L (+) glutamic acid in a membrane-integrated bioreactor

Modelling and simulation of direct and continuous production of L (+) glutamic acid under non-neutralizing conditions in a membrane-integrated bioreactor was done. The model describes a green and continuous process using sugarcane juice as a cheap and renewable carbon source for its microbial conversion to glutamic acid. Provisions of continuous withdrawal of product and downstream separation and recycle of microbial cells and unconverted carbon source allowed sustained production without pH adjustment. Appropriate microfiltration and nano-filtration membrane modules did the separation job efficiently. The model developed with extended Nernst-Planck approach captured the relevant transport phenomena along with fermentation kinetics under substrate-product inhibitions. Performance of the model is well reflected in low relative error (<0.05), high Willmott index (d > 0.97) and high overall correlation coefficient (R2 > 0.98). The modelled system produced glutamic acid with a productivity of 8.2 g/ (L h) and yield of 0.95 g/g at a reasonably high flux of 75 L/(m2 h) under a transmembrane pressure of only 14-15 bar. The final product was obtained at a concentration of 55 g/L and could easily be concentrated further by an additional nanofiltration step.