Enhanced Organically Bound Selenium Yeast Production by Fed-Batch Fermentation

This study describes a fed-batch fermentation protocol for enhanced production of Saccharomyces cerevisiae containing organically bound selenium. Two levels of sodium selenate concentrations were applied as either a single dose or continuous addition. Fermentations with high sodium selenate (63.2 g/L in cane molasses feeding medium) demonstrated 24 g/L of biomass with 1382 μg of selenium/g of dry biomass for single-dose addition and 40 g/L of biomass with 1491 μg of selenium/g of dry biomass for continuous addition. Low selenium concentration (31.6 g/L in cane molasses feeding medium) demonstrated higher biomass concentration with higher selenium level; 37 g/L of biomass with 2846 μg of selenium/g of dry biomass and 45 g/L of biomass with 2495 μg of selenium/g of dry biomass for single-dose and continuous addition, respectively. Also, two adapted S. cerevisiae strains were evaluated in fed-batch fermentation. A single dose of low concentration demonstrated >3000 μg of selenium/g of dry biomass, but biomass concentration was lower (≤32 g/L) for these adapted strains. Keywords: Sodium selenate; selenium; yeast; Saccharomyces cerevisiae; fermentation