Abstract
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 Lactococcus lactis and Lactobacillus casei 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 Lactococcus lactis and Lactobacillus casei 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.
Highlights
Lactic acid bacteria (LAB) are gram-positive, facultatively anaerobic, usually nonmotile and nonsporulating bacteria, whose characteristic feature is production of lactic acid from carbohydrates by means of fermentation as their major end product [1, 2]
Our study revealed that L. lactis and L. casei isolated from milk and its products are good biosorbents of silver cations as they absorbed about 70–96% of silver from 1 ppm solution
We found that two investigated lactic acid bacteria, L. lactis and L. casei, had the ability to sorb silver cations which was most likely associated with the cell surface of bacterial strain evaluated using Transmission Electron Microscopy (TEM) examinations
Summary
Lactic acid bacteria (LAB) are gram-positive, facultatively anaerobic, usually nonmotile and nonsporulating bacteria, whose characteristic feature is production of lactic acid from carbohydrates by means of fermentation as their major end product [1, 2]. This capability and other features have led to the wide use of LAB in numerous industrial applications. LAB have been recognized in the field of bioremediation, especially when bacterial strains act as sorbents [7,8,9]. Chromium resistant Lactobacillus strains have displayed their ability to reduce chromium(VI) to chromium(III) [12]. Biosorption mechanism of silver cations by Lactobacillus sp. strain A09 was investigated in the study of Lin et al [14]
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