Identification of lactic acid bacteria using FTIR spectroscopy and cluster analysis

Fourier-transform infrared (FTIR) spectroscopy and cluster analysis were applied to differentiate and identify lactic acid bacteria of different Lactobacillus, Lactococcus, Leuconostoc, Pediococcus and Streptococcus strains at the genus level, and Lactobacillus strains at the species level. A previously developed method for measuring FTIR spectra and a strategy for their analysis were used for selecting FTIR spectra of examined strains, and creating a spectral library. This library contains 1500 FTIR spectra and their derivatives. It was found that combinations of the polysaccharide region (1200–900 cm−1) with the fingerprint region (900–700 cm−1) and the mixed region (1500–1200 cm−1) of the spectra, and their first derivatives, were the most useful for characterizing the FTIR spectra of selected microorganisms. A description of spectra of lactic acid bacteria, applying the differentiation index D calculated on the basis of the Pearson correlation, allowed correct identification of bacterial genera, except for Lactobacillus strains, where identification was limited to the species level.