Indirect measurement of water content in an aseptic solid substrate cultivation pilot-scale bioreactor

A lack of models and sensors for describing and monitoring large-scale soli d substrate cultivation (SSC) bioreactors has hampered industrial developme nt and application of this type of process. This study presents an indirect dynamic measurement model for a 200-kg-capacity fixed-bed SSC bioreactor u nder periodic agitation. Growth of the filamentous fungus Gibberella fujiku roi on wheat bran was used as a case study. Real data were preprocessed usi ng previously reported methodology. The model uses CO, production rate and inlet air conditions to estimate average bed water content and average bed temperature. The model adequately reproduces the evolution of the average b ed water content and can therefore be used as an on-line estimator in pilot -scale SSC bioreactors. To obtain a reasonable fit of the bed temperature, however, inlet air humidity measurements will have to be adjusted with a da ta reconciliation algorithm. Good estimation of temperature is important fo r the future design of improved water content estimation using state observ ers. The model also provides insight into understanding the complex behavio r of the dynamic system, which could prove useful when establishing advance d model-based operational and control strategies. (C) 2001 John Wiley & Son s, Inc.