TY - JOUR A1 - Koegler, M. A1 - Paul, Andrea A1 - Anane, E. A1 - Birkholz, M. A1 - Bunker, A. A1 - Viitala, T. A1 - Maiwald, Michael A1 - Junne, S. A1 - Neubauer, P. T1 - Comparison of time-gated surface-enhanced Raman spectroscopy (TG-SERS) and classical SERS based monitoring of Escherichia coli cultivation samples JF - Biotechnology progress N2 - The application of Raman spectroscopy as a monitoring technique for bioprocesses is severely limited by a large background signal originating from fluorescing compounds in the culture media. Here, we compare time-gated Raman (TG-Raman)-, continuous wave NIRprocess Raman (NIR-Raman), and continuous wave micro-Raman (micro-Raman) approaches in combination with surface enhanced Raman spectroscopy (SERS) for their potential to overcome this limit. For that purpose, we monitored metabolite concentrations of Escherichia coli bioreactor cultivations in cell-free supernatant samples. We investigated concentration transients of glucose, acetate, AMP, and cAMP at alternating substrate availability, from deficiency to excess. Raman and SERS signals were compared to off-line metabolite analysis of carbohydrates, carboxylic acids, and nucleotides. Results demonstrate that SERS, in almost all cases, led to a higher number of identifiable signals and better resolved spectra. Spectra derived from the TG-Raman were comparable to those of micro-Raman resulting in well-discernable Raman peaks, which allowed for the identification of a higher number of compounds. In contrast, NIR-Raman provided a superior performance for the quantitative evaluation of analytes, both with and without SERS nanoparticles when using multivariate data analysis. KW - Time-gated Raman (TG-Raman) KW - Surface-enhanced Raman spectroscopy (SERS) KW - Multivariate data analysis KW - Metabolite quantification KW - Escherichia coli PY - 2018 DO - https://doi.org/10.1002/btpr.2665 SN - 1520-6033 SN - 8756-7938 VL - 34 IS - 6 SP - 1533 EP - 1542 PB - Wiley AN - OPUS4-45831 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -