DIRECT COMPARISON OF 4 DIFFERENT BIOMASS ESTIMATION TECHNIQUES AGAINST CONVENTIONAL DRY-WEIGHT MEASUREMENTS

Many indirect biomass estimation techniques have been discussed in the literature; however, a comparison of the applicability of these metho ds for bioprocess control purposes has not been discussed comprehensiv ely. In this paper, four different uncomplicated biomass measurement t echniques were directly compared with the conventional biomass dry wei ght measurement, and the possibilities of their implementation in proc ess control environments is discussed. These techniques are estimation s based on laser turbidimeter signals, measurement of cell numbers and sizes, estimations based on the oxygen mass balance, and, finally, es timations based on the base consumption during pH control. All these t echniques led to essentially the same quality of estimations. The comp arisons were performed in experiments with two bacteria strains. Cross -validation analyses showed that all measurements are sufficiently acc urate 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.