Rapid analysis of the expression of heterologous proteins in Escherichia coli using pyrolysis mass spectrometry and Fourier transform infrared spectroscopy with chemometrics: application to alpha 2-interferon production

Cell pastes and supernatant Escherichia coli samples, taken from an industr ial bioprocess overproducing recombinant alpha 2 IFN were analysed using py rolysis mass spectrometry (PyMS) and diffuse reflectance-absorbance Fourier transform infrared spectroscopy (FT-IR). PyMS and FT-IR are physico-chemic al methods which measure predominantly the bond strengths of molecules and the vibrations of bonds within functional groups, respectively. They theref ore give quantitative information about the total biochemical composition o f the bioprocess sample. The interpretation of these hyperspectral data, in terms of the quantity of alpha 2 IFN in the cell pastes and supernatant sa mples was possible only after the application of the 'supervised learning' methods of artificial neural networks (ANNs) and partial least squares (PLS ) regression. Both PyMS and FT-IR are novel, rapid and economical methods f or the screening and the quantitative analysis of complex biological biopro cess over producing recombinant proteins. Models established using either s pectral data set had a similarly satisfactory predictive ability. This show s that whole-reaction mixture spectral methods, which measure all molecules simultaneously, do contain enough information to allow their quantificatio n when the entire spectra are used as the inputs to methods based on superv ised learning. Moreover, this is the first study where FT-IR in the mid-IR range has been used to quantify the expression of a heterologous protein di rectly from fermentation broths and the first study to compare the abilitie s of PyMS and FT-IR for the quantitative analyses of an industrial bioproce ss. (C) 1999 Elsevier Science B.V. All rights reserved.