Selenium stress response of the fruit origin strain Fructobacillus tropaeoli CRL 2034.

The fruit-origin strain Fructobacillus tropaeoli CRL 2034 can biotransform selenium into seleno-nanoparticles and selenocysteine. The proteomic analysis of F. tropaeoli CRL 2034 exposed to 5 and 100 ppm of Se showed a dose-dependent response since 19 and 77 proteins were deregulated, respectively. In the presence of 5 ppm of Se, the deregulated proteins mainly belonged to the categories of energy production and conversion or had unknown functions, while when cells were grown with 100 ppm of Se, most of the proteins were grouped into amino acid transport and metabolism, nucleotide transport and metabolism, or into unknown functions. However, under both Se conditions, glutathione reductases were overexpressed (1.8-3.1-fold), while mannitol 2-dehydrogenase was downregulated (0.54-0.19-fold), both enzymes related to oxidative stress functions. Mannitol 2-dehydrogenase was the only enzyme found that contained SeCys, and its activity was 1.27-fold increased after 5 ppm of Se exposure. Our results suggest that F. tropaeoli CRL 2034 counteracts Se stress by overexpressing proteins related to oxidative stress resistance and changing the membrane hydrophobicity, which may improve its survival under (food) storage and positively influence its adhesion to intestinal cells. Selenized cells of F. tropaeoli CRL 2034 could be used for producing Se-enriched fermented foods. KEY POINTS: • Selenized cells of F. tropaeoli showed enhanced resistance to oxidative stress. • SeCys was found in the Fructobacillus mannitol 2-dehydrogenase polypeptide chain. • F. tropaeoli mannitol 2-dehydrogenase activity was highest when exposed to selenium.

Selenium and mercury concentration in drinking water and food samples from a coal mining area in Brazil.

Selenium (Se) is an essential element for human health and can also alleviate the toxicity of elements such as mercury (Hg), which is considered deleterious to health. The study area is an important coal mineral region in Brazil, generating 40% of all Brazilian coal. During the coal mining process, Se and Hg are released, which can induce potential human health risks via the food chain. The purpose of the present study is to determine total Se and its species and total Hg in drinking water and food locally produced from a coal mining area, to assess the impact of coal mining. The samples were collected in two cities, with and without coal mining influence. Total Se levels in drinking water and food were assessed by inductively coupled plasma mass spectrometry (ICP-MS) and its species by high-performance liquid-ICP-MS, while total Hg was determined by cold vapor atomic fluorescence spectrometry. Drinking water (1.1 ± 0.2 mg L-1 dry weight) (p = 0.02) and tomatoes (1.5 ± 0.1 mg kg-1 dry weight) (p = 0.01) from the coal mining area had higher total Se concentration than the control area. The highest Se concentrations were found in animal-based food (6.4 ± 0.8 mg kg-1 dry weight) with an important contribution of Se IV (65%). The analyzed sample did not accumulate a significant amount of Hg. Future studies on the estimates of daily intake of these elements and dietary pattern of the population are needed to make appropriate dietary recommendations and support public health action.