Real time detection and quantification of inclusion bodies expressed in Escherichia coli by impedance measurements

Escherichia coli expressing human growth hormone as inclusion bodies was cu ltured in a fermenter. Real time, non-invasive detection and quantification of inclusion body protein expressed in E. coli was performed by impedance measurements at 50 MHz and 180 MHz. At 50 MHz rotation of dipoles of the pr otein and their proton fluctuation, i.e., beta -dispersion of protein aggre gates formed inside the cell as a result of expressed protein, results in a n additional decrease in impedance. At 180 MHz the impedance remained at a plateau. In a high cell density E. coli culture, after induction with IPTG, when the cell mass remained unchanged, an increase in the magnitude of bet a -dispersion was observed at 50 MHz. This was due to the formation and sub sequent increase in the concentration of r-human growth hormone which aggre gate as inclusion bodies. The estimation of inclusion bodies by taking the ratio of impedance at 180 MHz and at 50 Mhz matched with the amount of prot ein estimated after extraction and purification (coefficient of correlation was 0.92). This is the first report of real time detection and monitoring of recombinant protein expressed as inclusion bodies by impedance measureme nts.