Chemometric analysis of FTIR and Raman spectra of the S-layer proteins of Lactobacillus

P. MOBILI, A. GOMEZ ZAVAGLIA AND C. ARAUJO ANDRADE.

Londres

Congreso; 21st International Conference on Raman Spectroscopy. Agosto de 2008. Londres, UK.; 2008

ICORS

Bacteria of genus Lactobacillus are commonly found in dairy products, and are usually associated with the beneficial effects of these products to human health. This beneficial activity is at least partially related with bacterial surface properties as adhesion and aggregation. Some lactobacilli bear an S-layer, a crystalline bidimensional array of glycoproteic subunits linked non-covalently to each other and to the underlying cell wall. As the outermost envelope in lactobacilli, S-layer could play an important role in the surface properties of these bacteria. Structural differences in S-layer proteins could be responsible for the observed variability in surface properties of different strains of lactobacilli1-2. FTIR is a well-established methodology that has been extensively used for the elucidation and analysis of the secondary structure of proteins3. On the other hand Raman has been used for microorganism characterization and differentiation4, and characterization of proteins5. In this study, chemometric analysis6 was conducted over the Raman and FTIR spectra of reference strains L. brevis ATCC 8287 and L. kefir JCM 5818, and from four strains of L. kefir isolated from kefir at CIDCA (L. kefir CIDCA 83113, CIDCA 8321, CIDCA 8344 and CIDCA 8348), in order to identify spectral differences correlated with the structure and composition of the S-layer. The scores plots obtained by PCA and PLS-DA, allowed us to discriminate and classify among lactobacilli species and aggregation grades, as can be seen in the figures 1 and 2. Moreover, the loading plots shows the spectral regions that contain the information related with the lactobacilli species and aggregation properties.