"Discrimination of Heterofermentative Lactobacilli by Means of Chemometrics and Raman Spectroscopy"

C. ARAUJO-ANDRADE, P. MOBILI, C. FRAUSTO-REYES, R. IVANOV-TSONCHEV, G. L. DE ANTONI, AND A. GÓMEZ ZAVAGLIA

Coimbra

Congreso; XIVth European Conference on the Spectroscopy of Biological Molecules.; 2011

ECSBM

In this work, a method based on Raman spectroscopy in combination with chemometrics such as PCA and PLS-DA, has been developed for differentiation of heterofermentative related lactobacilli (1). In a first approach, Lactobacillus kefir strains were discriminated from Lactobacillus parakefir and Lactobacillus brevis. Afterwards, PCA allowed for a clear differentiation between Lb. parakefir and Lb.brevis. For the first level of discrimination, PCA was performed on the whole spectra and also on delimited regions, defined taking into consideration the loading values (2). The best regions allowing a clear differentiation between Lb. kefir and non- Lb. kefir strains were found to be: the 1700-1500 cm-1, 1500-1185 cm-1 and 1800-400 cm-1. In order to develop a classification rule, PLS-DA was carried out on the mentioned regions. This method allowed the discrimination and classification of the strains in two groups: Lb. kefir and non- Lb. kefir. The model was further validated using lactobacilli strains from different culture collections or strains isolated from kefir grains previously identified using molecular methods. The second approach based on PCA was also performed on the whole spectra and on delimited regions, being the regions 1700-1500 cm-1, 1500-1185 cm-1 and 1185-1020 cm-1 the ones allowing the clearest discrimination between Lb. parakefir and Lb. brevis. The results obtained in this work, allowed a clear discrimination within heteroferementative lactobacilli strains, being proteins, the biological structures the most determinant for this discrimination (3).