Abstract
The instrumentation of an industrial air lift fermenter used for lactic yeast production on whey substrates is described. Different types of biomass sensors adapted for industrial plant use were tested. A sensor based on optical density measurement was first studied on-line. In view of poor results due to interference by hydrodynamics, an automatic at-line biomass sensor adapted to industrial conditions was designed. The setting-up and performance of that sensor are described and the influence of interfering factors on its operation is discussed. The accuracy, in terms of biomass concentration was found to be better than ±1 g l −1. The implementation of software-based analysers using classical measurement and a knowledge-based process dynamic model was also studied. Uncertainty was ≈5% of the measured value. The performance of the different sensors was compared with that of the NADH fluorosensor.
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