Biotransformation and accumulation of selenium by fructophilic lactic acid bacteria

F G MARTINEZ; M PESCUMA; F MOZZI

Egmond aan Zee

Simposio; 12th International Symposium on Lactic Acid Bacteria; 2017

Selenium (Se) is an essential trace element incorporated in humans through vegetable and fruit ingestion and is present in proteins as SeCys. Some lactic acid bacteria (LAB) can accumulate and biotransform Se into SeCys and can synthesize nanoparticles. Fructobacilli are fructophilic LAB mainly isolated from plant sources. In this work we aimed to study the ability of fruit origin Fructobacillus strains to accumulate and biotransform Se into organic forms and nanoparticles. Nine strains of Fructobacillus isolated from fig, custard apple and khaki were grown in the presence of Na2SeO3. The amount of intracellular Se and SeCys was determined by ICP-MS while the formation of Se nanoparticles was visualized by SEM. The remaining Se in the supernatants was measured by the 2,3-diaminonaphthalene method. All strains showed similar growth behavior when 20 ppm Se was added in the medium as compared to the control without Se. The percentage of Se biotransformation was between 41.3 and 83.1 %. F. tropaeoli CRL 2034, the strain that showed the highest Se accumulation value, could grow in the presence of 200 ppm Se although one log U decrease in the cell viability was observed at 24 h when 60 ppm Se was added. As the maximum daily intake of Se for human consumption is 5 ppm, this value was used in further studies. ICP-MS results indicated that the Fructobacillus strain could accumulate 10 % of the added Se from which 1.5 % was transformed into SeCys. Moreover, the strain was able to produce spherical nanoparticles without affecting the cell morphology. Our results suggest that F. tropaeoli CRL 2034 could be used to produce Se nanoparticles or Se-enriched fruit-based foods.