CERELA   05438
CENTRO DE REFERENCIA PARA LACTOBACILOS
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Biotransformation of selenium by Lactobacillus reuteri CRL 1101 and Lactobacillus acidophilus CRL 636
Autor/es:
PESCUMA M.; PEREZ CORONA T.; FONTA G; MADRID Y; GOMEZ GOMEZ B.; MOZZI F
Lugar:
San Miguel de Tucuman
Reunión:
Simposio; V Simposio Internacional de Bacterias Lacticas; 2016
Resumen:
Selenium (Se), an essential trace element, is present as SeCys (Sec, amino acid) in proteins (selenoproteins) involved in antioxidant functions, thyroid hormone production, viral expression genes, etc. Se should be consumed as elemental or organic form to be non-toxic. Animals incorporate Se via plants that absorb Se from the soil and transform inorganic Se into organic forms such as methylated low-molecular-weight selenium compounds (selenomethionine, SeMet) which is a precursor for Sec. In addition, some lactic acid bacteria are able to bio-transform Se into elemental Se nanoparticles, SeCys2, SeMeSeCys and SeMet; these compounds being known to have antioxidant properties and to arrest the cell cycle of cancer cells. The aim of this work was to evaluate the ability of Lactobacillus reuteri CRL 1101 and Lactobacillus acidophilus CRL 636, species commonly used in fermented foods, to transform and accumulate Se. The strains were grown in MRS supplemented with 5 mg/L of SeO3Na2 at 37°C during 24 h. Cell viability was monitored by cell count (cfu/mL) and OD600. The release of elemental Se as nanoparticles was analyzed by TEM (JOEL JEM 2100) equipped with an X-ray energy dispersive (XEDS) microanalysis composition system. Se accumulation was analyzed by ICP-MS (Agilent 7700) after total microwave digestion, and Se species by using an LC-ICP-MS with a reverse phase C8 and an ion exchange column (PRP-X100) after enzymatic digestion. Results showed that viability of L. reuteri CRL 1101 after 24 h incubation in the presence of Se was 1 U log lower than in the control, while a greater deleterious effect (3 U log) of Se was observed in L. acidophilus CRL 636. TEM analysis showed the presence of spherical Se nanoparticles with sizes between 25 and 130 nm in both cell cultures. Interestingly, in L. reuteri CRL 1101 cultures nanoparticles were embedded in a carbon matrix of likely exopolysaccharides; this feature was not observed in L. acidophilus CRL 636 for which cell lyses was detected. L. reuteri accumulated 78% of the added Se in the cell while L. acidophilus CRL 636 41% after 24 h incubation. LC-ICP-MS analysis showed that both stains were able to accumulate Se intracellularly as SeCys2 and SeMet while the presence of SeMeSeCys was observed only in L. reuteri CRL 1101. These strains could be used to formulate Se-enriched foods for delivering these antioxidant compounds to individuals with Se deficiencies.