At-line monitoring of a submerged filamentous bacterial cultivation using near-infrared spectroscopy

The use of near infra-red spectroscopy (NIRS) to monitor a submerged filame ntous bacterial bioprocess was investigated. An industrial strain of the fi lamentous bacterium Streptomyces fradiae was cultured in a 12 litre stirred tank reactor (STR) using a complex medium. This mycelial 4 phase toil, wat er, gas and solid) system produced highly complex and variable matrices, th erefore monitoring such a complex fluid with NIRS represented a considerabl e challenge. Nevertheless, successful models for four key analytes (methyl oleate, glucose, glutamate and ammonium) were built at-line (rapid off-line ) using NIRS. In the present study, the methods used to formulate, select a nd validate the models for the key analytes are discussed, with particular emphasis on how the model performance can be critically evaluated. Since pr evious reports on NIRS in monitoring bioprocesses have either involved simp ler matrices, or, in filamentous systems, have not discussed how NIRS model s can be critically assessed, the emphasis in the present study on providin g an insight into the modelling process in such a complex matrix, may be pa rticularly important to the applicability of NIRS to such industrial biopro cesses. (C) 2000 Elsevier Science Inc. All rights reserved.