Evaluation of on-line viable biomass measurements during fermentations of Candida utilis

In this article the suitability of the Biomass Monitor for on-line measurem ent of viable biomass is thoroughly evaluated during aerobic fermentations of Candida utilis. Successively a number of specifications of the measuring device are discussed for the studied biological system. The optimal measur ement frequency for the given experimental conditions is determined. Furthe rmore, reliable calibrations of the capacitance readings versus well-known off-line analysis of dry weight and plate counts of the yeast have been est ablished. In addition, the impact of varying fermentation conditions such a s stirrer speed and air flow rate together with the influence of the oxygen concentration and conductance of the medium on the capacitance signal have been studied and quantified when a significant influence was observed. It is illustrated that knowledge of the viable biomass during fermentations is very useful in the estimation of the specific growth rate of the organism.