Development of a Method Based on Chemometric Analysis of Raman Spectra for the Identification of Lactobacillus kefir Isolated from Kefir Grains

P. MOBILI, C. ARAUJO-ANDRADE, A. LONDERO, C. FRAUSTO REYES, E. A. ARAIZA-REYNA, F. RUIZ, J. R. MARTÍNEZ-MENDOZA, G. DE ANTONI AND A. GÓMEZ-ZAVAGLIA.

INTERNATIONAL JOURNAL OF FOOD MICROBIOLOGY

Amsterdam, Elsevier

Lugar: enviado FOOD-S-10-00316; Año: 2009 p. 1 - 2

0168-1605

In this work, an approach based on Raman spectroscopy in combination with Principal Component Analysis (PCA) and Partial Least Square-Discriminant Analysis (PLS-DA) has been developed for the rapid differentiation of Lactobacillus kefir from other species of lactobacilli isolated from kefir grains: Lactobacillus parakefir, Lactobacillus brevis and Lactobacillus plantarum. The raw spectra depicted clear differences among the lactobacilli species analyzed, which were investigated using Principal component analysis (PCA). PCA was performed on the whole spectra and also on delimited regions, defined taking into consideration the loading values. The best regions allowing a clear differentiation between L. kefir and non -L. kefir strains were found to be: the 1700-1500, 1500-1185 and 1800-400 (whole spectrum) cm-1 Raman ranges. In order to develop a classification rule, PLS-DA was carried out on the mentioned regions. This method permitted the discrimination and classification of the strains under study in two groups: L. kefir and non- L. kefir. The model was further validated using different lactobacilli strains culture collection or strains isolated from kefir grains previously identified using molecular methods (Delfederico et al. 2006; Garrote et al. 2001; Golowczyc et al. 2008). After validation, the spectra corresponding to other strains isolated from kefir grains were registered. The results obtained allowed a clear discrimination for L. kefir strains, being the 1700-1500 cm-1 region the one with the highest discriminating power (95 % sensitivity and 95 % specificity). Taking into account the complexity of kefir microbiota and the influence of culture conditions on its composition, as well as the difficulties associated with the discrimination between lactobacilli species phylogenetically closely related by means of the traditional biochemical or molecular methods, the development of a reliable non-destructive and less time-consuming method of classification results a very useful tool for the analysis of unknown samples, allowing researchers to save time and efforts.