Direct comparison of four different biomass estimation techniques against conventional dry weight measurements

Abstract

Many indirect biomass estimation techniques have been discussed in the literature; however, a comparison of the applicability of these methods for bioprocess control purposes has not been discussed comprehensively. In this paper, four different uncomplicated biomass measurement techniques were directly compared with the conventional biomass dry weight measurement, and the possibilities of their implementation in process control environments is discussed. These techniques are estimations based on laser turbidimeter signals, measurement of cell numbers and sizes, estimations based on the oxygen mass balance, and, finally, estimations based on the base consumption during pH control. All these techniques led to essentially the same quality of estimations. The comparisons were performed in experiments with two bacteria strains. Cross-validation analyses showed that all measurements are sufficiently accurate for process supervision and control purposes. The final decision about implementation of one of the techniques discussed must be made under consideration of the available equipment, the microorganisms to be cultivated and the cultivation conditions.