An electrodeless, inductive permittivity probe phases of the fermentation as well as various downis shown to reliably indicate fermentation biomass. By stream processing unit operations (monitoring of recomdesigning the probe based on electromagnetic induction, binant E. coli lysis during homogenization or hybridoma the electrode polarization artifact-common to electrodeviability during antibody ultrafiltration, etc.). based permittivity measurements of conductive solu-
The use of permittivity is attractive because the bulk tions-is eliminated. The measurement of viable biomass concentration (X V ) is precise and linear, with negligible permittivity of a fermentation broth is linear up to high interference, as shown for two bacteria, two yeasts, and X V (Mishima et al., 1991b;Pauly et al., 1960; Sugiura two mammalian cells. The permittivity spectra often can et al., 1964) and selective for viable biomass (Asami, be described by the three parameters of the Cole-Cole 1977a; Austin et al., 1994;Sugiura and Koga, 1965), equation: the maximum (low-frequency) permittivity, the i.e., dead cells with leaky membranes, cell debris, and characteristic frequency ( f C ), and the Cole-Cole β£. The f C and β£ have potential as relative indicators of cell size and particulate matter do not affect the measurement, which morphology, respectively.