INVESTIGADORES
GOMEZ ZAVAGLIA Andrea
artículos
Título:
Use of Raman Spectroscopy and Chemometrics for the Quantification of Metal Ions Attached to Lactobacillus kefir
Autor/es:
E. GERBINO, P. MOBILI, E. TYMCZYSZYN, C. FRAUSTO REYES, C. ARAUJO-ANDRADE, A. GÓMEZ ZAVAGLIA
Revista:
JOURNAL OF APPLIED MICROBIOLOGY
Editorial:
WILEY-BLACKWELL PUBLISHING, INC
Referencias:
Lugar: Journal of Applied Microbiology. (2012) 112: 363-371; Año: 2012 vol. 112 p. 363 - 371
ISSN:
1364-5072
Resumen:
Aims: To set-up an experimental and analytical methodology to evaluate the
feasibility of developing simple, accurate and quantitative models based on
Raman spectroscopy and multivariate analysis for the quantification of metal
ions adsorbed to the bacterial surface of Lactobacillus kefir.
Methods and Results: One millilitre cultures from two strains of Lact. kefir in
the stationary phase were harvested and washed twice with ultra pure water.
The bacterial pellets were resuspended into 1 ml solutions of Pb+2, Cd+2 or
Ni+2 ranging from 0 to 0Æ9 mmol l)1. The suspensions were further incubated
for 1 h at 30C at pH 5Æ5. After centrifugation, the pellets were kept to register
the Raman spectra and the supernatants were used for the analytical determi-
nation of Pb+2, Cd+2 and Ni+2. Micro-organisms nontreated with metal ions
were used as controls. Principal component analysis (PCA) was performed over
the preprocessed Raman spectra to evaluate whether the clusters obtained could
be correlated with the concentration of metal ions attached to the bacterial bio-
mass. After that, partial least squares (PLS) models were calibrated with the
aim of quantifying the metal ions adsorbed to the bacterial surface. According
to the analytical determinations, the maximum binding capacity of all the met-
als (qmax) attained values that are comparable with those observed for other
lactic acid bacteria (ca. 0Æ200 mmol g)1). The spectral analysis revealed that the
main functional groups involved in the bacteria ⁄ metal interaction are carboxy-
lates, phosphates and polysaccharides. In PCA, the first two principal compo-
nents explain more than 72% variance of the spectral data set contained in the
data structure, allowing a clear discrimination among samples of different con-
centrations. Based on this information and using as reference the results
obtained by analytical methods, PLS prediction models were successfully
defined for the quantification of Pb+2, Cd+2 and Ni+2 attached to the bacterial
surface.
Conclusions: The calibration and validation of methods based on multivariate
analysis allowed the definition of models for the quantification of Pb+2, Cd+2
and Ni+2 attached to bacterial surfaces. The high percentages of explained vari-
ances in PCA gave a strong support to calibrate the prediction models, depict-
ing very good correlations with the reference method (correlations 0Æ90 in all
cases).
Significance and Impact of the study: Lactobacillus kefir CIDCA 8348 and JCM
5818 bind Pb+2, Cd+2 and Ni+2 in an efficient way. This fact gives support for
their potential use as sequestrants of traces of these metals in products
addressed to human and animal consume. The prediction models developed would be useful for the determination of the investigated metal ions in
unknown samples giving at the same time, structural information about this
interaction. This is certainly the most important contribution of this work.