Biosorption of silver cations onto <i>Lactococcus lactis</i> and <i>Lactobacillus casei</i> isolated from dairy products

<div><p>The current work deals with the phenomenon of silver cations uptake by two kinds of bacteria isolated from dairy products. The mechanism of sorption of silver cations by <i>Lactococcus lactis</i> and <i>Lactobacillus casei</i> bacteria was investigated. Inductively coupled plasma–mass spectrometry (ICP-MS) was used for determination of silver concentration sorbed by bacteria. Analysis of charge distribution was conducted by diffraction light scattering method. Changes in the ultrastructure of <i>Lactococcus lactis</i> and <i>Lactobacillus casei</i> cells after treatment with silver cations were investigated using transmission electron microscopy observation. Molecular spectroscopy methods, namely Fourier transform-infrared spectroscopy (FT-IR) and matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS) were employed for description of the sorption mechanism. Moreover, an analysis of volatile organic compounds (VOCs) extracted from bacterial cells was performed.</p></div

A spectrum of <i>L</i>. <i>lactis</i> recorded using MALDI-TOF MS technique with the use of DHB (top) and HCCA (bottom) matrix; photos of crystals of the matrices are shown in the corner.

<p>A spectrum of <i>L</i>. <i>lactis</i> recorded using MALDI-TOF MS technique with the use of DHB (top) and HCCA (bottom) matrix; photos of crystals of the matrices are shown in the corner.</p

Concentration of Ag in OPTION 1 & 2 measured using ICP-MS.

<p>Concentration of Ag in OPTION 1 & 2 measured using ICP-MS.</p

Comparative viability of <i>L</i>. <i>lactis</i> and <i>L</i>. <i>casei</i> cells after the treatment with AgNO₃ (1 ppm) regarding the first (OPTION 1) and the second method (OPTION 2).

<p>Comparative viability of <i>L</i>. <i>lactis</i> and <i>L</i>. <i>casei</i> cells after the treatment with AgNO₃ (1 ppm) regarding the first (OPTION 1) and the second method (OPTION 2).</p

Chromatogram of VOCs from <i>L</i>. <i>lactis</i> obtained using HS-SPME-GC/MS, where: (1) acetaldehyde, (2) ethanol, (3) butane, (4) acetone, (5) 2-methylpropanal, (6) ethenyl acetate, (7) 2-butanone, (8) ethyl acetate, (9) hexane, (10) 3-methylbutanal, (11) 1-pentanol, (12) 3-methyl-1-butanol, (13) 2-phenylethyl acetate.

<p>Chromatogram of VOCs from <i>L</i>. <i>lactis</i> obtained using HS-SPME-GC/MS, where: (1) acetaldehyde, (2) ethanol, (3) butane, (4) acetone, (5) 2-methylpropanal, (6) ethenyl acetate, (7) 2-butanone, (8) ethyl acetate, (9) hexane, (10) 3-methylbutanal, (11) 1-pentanol, (12) 3-methyl-1-butanol, (13) 2-phenylethyl acetate.</p

A spectrum of <i>L</i>. <i>casei</i> recorded using MALDI-TOF MS technique on DHB (top) and HCCA (bottom) matrix; photos of crystals of the matrices are shown in the corner.

<p>A spectrum of <i>L</i>. <i>casei</i> recorded using MALDI-TOF MS technique on DHB (top) and HCCA (bottom) matrix; photos of crystals of the matrices are shown in the corner.</p

OD values for the studied strains of bacteria inoculated with different concentrations of silver.

<p>OD values for the studied strains of bacteria inoculated with different concentrations of silver.</p