Abstract: Lactobacillus rhamnosus (ATCC 53103) was cultured 37 ℃ in an MRS medium containing 1 mL of 6% NaCl per 15 mL and 10 μg/mL sodium selenite at pH 6.4. The selenium content of the dried biomass was determined to be up to 452.43 μg/g by inductively coupled plasma-atomic emission spectrometry and the selenium enrichment efficiency was calculated as 43.33%. Compared with the unstressed control group, the selenium content and selenium enrichment efficiency were improved by 122.72 μg/g and 13.17%, respectively. Black microparticles were observed both inside and outside the selenium-enriched L. rhamnosus cells by transmission electron microscopy, which was proved to be elemental selenium by energy dispersive X-ray spectroscopy (EDAX). The selenium content increased after salt stress, which further proved that salt stress promoted the selenium enrichment of L. rhamnosus.

Key words: Lactobacillus rhamnosus, selenium, biotransformation, salt stress