Simultaneous determination of multiple components in lactic acid fermentation using FT-MIR, NIR, and FT-Raman spectroscopic techniques

Bioprocess optimization is often limited by its inability to measure biomas s, nutrients and product concentrations in a time frame that allows process adjustments. Infrared spectroscopic techniques can potentially be used to measure each of these components within about 3 min of sampling, of an unpr ocessed whole broth sample. In the present study, the use of Fourier transf orm mid infrared (FT-MIR), near infrared red (NIR), and Fourier transform ( FT)-Raman spectroscopic techniques for at-line (rapid off-line) monitoring of biomass, glucose, and lactic acid in a lactic acid fermentation by Lacto bacillus casei was investigated. Suitable spectral wavenumber regions were selected for principal least square (PLS) regression and principal componen t regression (PCR) and calibration models were developed. The standard erro r of calibration for the PLS-1st derivative calibration models for glucose, lactic acid, and optical cell density were 2.5, 0.7 g/l, and 0.23, respect ively. Prediction errors were high for NIR and FT-Raman methods. Results in dicated that FT-MIR spectroscopy could be used for rapid detection of gluco se, lactic acid, and optical cell density during lactic acid fermentation. (C) 2001 Elsevier Science Ltd. All rights reserved.