Production of selenium-enriched biomass by Enterococcus durans

Area of Science:

• Microbiology
• Nutritional Science
• Biotechnology

Background:

• Selenium (Se) is an essential micronutrient with growing interest in dietary supplementation sources.
• Understanding microbial selenium bioaccumulation is crucial for developing novel Se-enriched foods and supplements.

Purpose of the Study:

• To evaluate the selenium bioaccumulation capacity of an Enterococcus strain, identified as Enterococcus durans (E. durans) LAB18s.
• To assess the potential of E. durans LAB18s as a source for organic dietary selenium.

Main Methods:

• Bacterial identification using VITEK® 2 system and 16S rDNA/16S-23S rDNA intergenic spacer (ITS) sequencing.
• Quantification of selenium (Se(IV)) bioaccumulation in E. durans LAB18s under varying sodium selenite concentrations.
• Optimization of growth and bioaccumulation conditions (pH, temperature) and time-course analysis.
• Scanning electron microscopy (SEM) to visualize cellular changes during selenium exposure.

Main Results:

• E. durans LAB18s demonstrated significant Se(IV) bioaccumulation, reaching 176.97 mg/g at 240 mg/l initial sodium selenite.
• Optimal bioaccumulation occurred at pH 7.0 and 30°C, with peak accumulation observed after 6 hours.
• SEM revealed cell-to-cell filaments in E. durans LAB18s grown with sodium selenite, indicating cellular interaction and Se absorption.

Conclusions:

• E. durans LAB18s exhibits a high capacity for bioaccumulating inorganic selenium (Se(IV)).
• The strain's ability to absorb considerable amounts of selenium supports its potential as a source of organic dietary selenium.
• This research highlights a promising avenue for developing bioavailable selenium supplements through microbial fermentation.