Monitoring of fermentation processes producing lactic acid bacteria by mid-infrared spectroscopy

Fourier transform mid-infrared (FT-MIR) spectroscopy was used to determine the concentrations of substrate, major metabolites and lactic acid bacteria in fermentation processes. Partial least-squares regression gave the following standard errors of prediction (SEP): 3.4 g/l for Iactose, 1.5 g/l for galactose, 0.9 g/l for lactic acid and 0.9 g/l for bacterial concentration. The principal vibrational assignments for the major compounds are provided. The spectra of filtered and non-filtered culture media containing lactic acid bacteria were not different with ordinary bacterial concentrations (up to IO g/l) using a transmission cell.