Chemometric analysis of FTIR and Raman spectra of lactobacilli isolated from kefir

P. MOBILI, C. ARAUJO, A. LONDERO, C. FRAUSTO REYES, G. DE ANTONI, A. GÓMEZ-ZAVAGLIA.

Sao Paulo

Congreso; SPEC 2008: Shedding Light on Disease: Optical Diagnosis for the New Millennium. Sao Jose dos Campos, Sao Paulo, Brazil. October 25-29, 2008.; 2008

SPEC

Modern technical developments have made Raman and FTIR spectroscopy fast, powerful and easy-to-use analytical techniques, combining detailed spectral fingerprints, non-destructivity and minimal sample preparation. Over the years, both methodologies have been developed and utilized for microbiological applications. Several research groups have already worked out identification procedures for bacteria using FTIR and Raman spectroscopies 1,2,3 For these purposes, spectroscopic information is considered as mathematical data on which chemometric techniques, such as Principal Component Analysis (PCA), Partial Least Square-Discriminant Analysis (PLS-DA) among others4 are applied, allowing discrimination and classification of bacteria at the species and even at the strain level5,6 In this work we analyzed the FTIR and Raman spectra of microorganisms from the genus Lactobacillus isolated from kefir, by means of chemometric methods like PCA and PLS-DA in order to discriminate and classify between Lactobacillus species. The microorganisms analyzed were grown in MRS broth at 30ºC, harvested at early stationary phase by centrifugation, washed twice with phosphate buffer (pH 7.0), resuspended in bidistilled water and lyophilized. Lyophilized bacteria were analyzed by FTIR and Raman spectroscopy. Chemometrics was used for the interpretation of the spectral differences observed in FTIR and Raman spectra. The analysis of the score plots obtained by PCA and PLS-DA, allowed us to discriminate and classify the strains investigated.