Use of at‐line and in‐situ near‐infrared spectroscopy to monitor biomass in an industrial fed‐batch Escherichia coli process

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Abstract
One of the key goals in bioprocess monitoring is to achieve real‐time knowledge of conditions within the bioreactor, i.e., in‐situ. Near‐infrared spectroscopy (NIRS), with its ability to carry out multi‐analyte quantification rapidly with little sample presentation, is potentially applicable in this role. In the present study, the application of NIRS to a complex, fed‐batch industrial E. coli (RV308/PHKY531) process was investigated. This process undergoes a series of temperature changes and is vigorously agitated and aerated. These conditions can pose added challenges to in‐situ NIRS. Using the measurement of a key analyte (biomass) as an illustration, the details of the relationship between the at‐line and in‐situ use of NIRS are considered from the viewpoint of both theory and practical application. This study shows that NIRS can be used both at‐line and in‐situ in order to achieve good predictive models for biomass. There are particular challenges imposed by in‐situ operation (loss of wavelength regions and noise) which meant the need for signal optimisation studies. This showed that whilst the at‐line modelling process may provide some useful information for the in‐situ process, there were distinct differences. This study shows that the in‐situ use of NIRS in a highly challenging matrix (similar to those encountered in current industrial practice) is possible, and thus extends previous works in the area. © 2002 Wiley Periodicals, Inc. Biotechnol Bioeng 80: 405–413, 2002.