## Reference  
1. Adamczyk, M.; Grabarczyk, M. Communication--Application of the Adsorptive Stripping Voltammetry to the Determination of Ti(IV) Content in Extracts of Stinging Nettle Leaves. _J. Electrochem. Soc._**2021**, _168_, 16505.  
_16.28. Selenium Bittransformation by Lactic Acid Bacteria, Bifidobacteria, and Yeats_  
**V. Kantorova 1,*, A. Kana 1, G. Krausova 2, I. Hyrslova 2 and O. Mestek 1**  
1 Faculty of Chemical Engineering, University of Chemistry and Technology Prague, 10000 Prague, Czech Republic  
2 Dairy research institute, Ltd., 10000 Prague, Czech Republic  
* Correspondence: kantorov@vscht.cz  
Selenium is an important trace element for human health. In its organic forms, such as selenoamino acids, occurs a component of selenoproteins and selenoenzymes, e.g., glutathione peroxidase, which is known for its antioxidative properties. The daily intake of selenium lower than 0.1 mg per kg of human body weight leads to selenium deficiency. This may cause several disorders of cardiac muscle. On the other hand, the intake over 1 mg per kg of body weight is considered toxic [1].  
Selenium is consumed from the food, and its natural sources are liver, sea food, and brazil nuts [2]. It is clear that these sources are not the usual example of daily meals of an average Czech person. The lack of selenium might be then compensated by food supplements, especially selenium enriched yeasts, which could accumulate up to 3 g\(\cdot\)kg\({}^{-1}\) of selenium [3]. However, the daily consumption of tablets is not the best \"user friendly\" way. Functional foods, such as dairy products, using selenium enriched lactic acid bacteria (LAB) and yeasts, is a promising approach. In our study, we obtain an overview as to how LAB and yeasts (15 strains, 8 genuses) incorporate and transform selenite after being exposed to selenium enriched growth media. The total content of selenium was determined by using inductively coupled plasma mass spectrometry (ICP-MS) after microwave assisteddigestion of the samples. The highest content of selenium, 45 mg.g\({}^{-1}\) (d.w.) was found in _Streptococcus thermophilus_, but most of the samples have an average content of Se lower than 1 mg.g\({}^{-1}\) (d.w.). Speciation analysis was performed by coupling ion pair reversed phase liquid chromatography with ICP-MS, after extraction with proteinase XXIII. Major species (abundance up to 60%) detected in _Bifidobacterium_ strains were selenocystine, selenomethionine, and one unknown species. Other detected species such as methylselenocysteine, selenite, and selenate were minor, with content in units of a percent. Most of the samples also showed the ability of producing selenium nanoparticles (SeNP). The transmission electron microscopy (TEM) provided an overview about the sizes and position of SeNP. It was shown that most of the strains produce Se NPs extracellularly, two strains can produce both intra- and extracellularly, and three strains do not produce any particles at all. Se NPs average diameter varies from 20 to 350 nm. The total content of selenium in nano form was determined using single-particle ICP-MS. This multiple-step analysis allowed us to determine the mass balance of various selenium forms in enriched LAB and yeasts.  
This research was funded by the program INTER-EXCELLENCE, subprogram INTER-COST of the Ministry of Education, Youth and Sport of the Czech Republic, grant No. LTC 20014 (COST CA18113), and by the grant of Specific university research (A1_FCHI_2021_003) and (A2 FCHI 2021 007).