ONLINE MONITORING OF CELL CONCENTRATIONS BY DIELECTRIC MEASUREMENTS

Dielectric measurements were made on solutions with cells to establish the feasibility of measuring on-line cell concentrations in bioreactors. Excellent linear relationships, in which correlation coefficients were more than 0.99, were obtained between values of electric capacitance (frequency range: 100 kHz to 10 MHz) and concentrations of yeast cells (immobilized in calcium alginate beads), Escherichia coli, Aspergillus niger, human leukemia (K562) cells, Madin-Darby bovine kidney (MDBK) cells on microcarriers and plant suspension cells of Sesamum indicum L. It was also found that the linearities were maintained practically under cultivating conditions in which temperature, pH, and salt and substrate concentrations were changing during cultivation. It is concluded that the dielectric measurement method is a promising method for estimating on-line cell concentrations in bioreactors.