¹³C MFA at high cell density cultivation of E. coli: Shake flasks are widely used for screening and optimization for scale up processes of industrial enzymes due to their easy handling and cost-effectiveness. To satisfy this enormous demand, a combination of recombinant DNA technology and largescale cell culture processes has helped achieve the growth of cells to high densities as well as enhanced protein production. My study focusses on developing fed batch process to attain high cell density and protein in E. coli BL21 (DE3) with the help of PreSens online monitoring device. Further it includes characterization of metabolic changes on induction of protein expression at high cell density using 13C metabolic flux analysis tool.