In vitro biosynthesis of organic selenium by Lactobacillus casei from inorganic selenium forms

The bioconversion of selenium in the form sodium selenite (Na2 SeO3 ) (SeIV) or selenate SeO4 (SeVI) to organic by Lactobacillus casei (L. casei) was investigated vitro. MRS media supplemented with 1, 2, 5, 10 20 ppm Se, inoculated 2% starter culture about 105 cfu/ ml L. and then incubated up 24 hrs at 37o C. Increasing “Se(IV)” concentrations markedly reduced bacterial growth compared “Se(VI)” indicating cytotoxic effect selenite. 5 more Se(IV) became reddish after hr incubation as a result formation 100-200 nanometer particles (SeNPs). Se speciation cultured supernatants its corresponding cell fractions carried out HPLC-ICP-MS technique. rate extremely higher than Se(VI) both fractions, however supernatant contained highest content. content resulted gradual increase concentration cells fractions. medium 1 completely depleted from inorganic it converted form. Although all only significant residual amount Our results demonstrate ability convert form(s) either inside cells. However, but not Se(VI), limit ppm, accumulated an fraction medium.