SELENIUM AND LACTOBACILLUS SPECIES

Selenium(Se) is an essential element for man and animal. Supplementation of Se has been done with Se-enriched yeast and inorganic Se compounds. In the present study a quantitative and qualitative evaluation was made of whether lactobacilli are able to concentrate Se. A high correlation was found between the bacterial Se concentration and the concentration of Se in the medium. The Se concentration in biomass was respectively 253 +/- 50, 375 +/- 33 and 407 +/- 108 mu g g(-1) dry weight for Lactobacillus delbrueckii subsp. bulgaricus, Lact. plantarum and Lact. casei subsp. casei when 1 mg 1(-1) Se4+ was present in the medium. Manganese (Mn) was concentrated in Lact. plantarum and Lact. casei subsp. casei but not in Lact. delbrueckii subsp. bulgaricus. The Mn concentration in biomass was higher compared to the Se concentration but this difference decreased when the concentration of Mn/Se increased in the culture medium. Copper, zinc and iron were also concentrated in biomass of Lact. delbrueckii subsp. bulgaricus. Characterization of the bacterial selenocompound revealed that Se-75 was generally incorporated, as selenocysteine, into protein of Lact. delbrueckii subsp. bulgaricus. Addition of L-cysteine to the medium decreased the bacterial Se content. It was concluded that Lact. delbrueckii subsp. bulgaricus incorporated Se non-specifically into bacterial protein. The application of Se-enriched lactobacilli (Se-Lb) in Se supplementation would be an interesting approach since selenomethionine, which is the major selenocompound in commercialized Se-yeast, was not detected in Se-Lb and because lactobacilli are already widely used in human nutrition.