Biofortification of Yeast with Selenomethionine in Corn Hydrolysate: Influence of Different Metabolic Pathways

Yeast biomass, the main protein source in distillers dried grains with solubles (DDGS), can be enriched with selenium (Se), enhancing the nutritional and functional value of this coproduct. Because Se deficiency affects large populations worldwide, Se-enriched yeasts represent a practical supplementation strategy, particularly in the organic form selenomethionine (SeMet), which is highly bioavailable. This study investigated Se accumulation and speciation in Saccharomyces cerevisiae Thermosacc^® strain cultivated in corn hydrolysate under aerobic (AE0, AE200, AE400) and anaerobic (AN0, AN200, AN400) conditions, with Na₂SeO₃ concentrations of 0, 200, and 400 mg L⁻¹. Cell performance, total Se, organic Se, and SeMet were quantified. The highest Se accumulation occurred at 400 mg L⁻¹, while 200 mg L⁻¹ favored more efficient conversion into organic forms. Aerobic metabolism supported superior intracellular concentrations (total Se: 6.15 mg g⁻¹; organic Se: 3.47 mg g⁻¹; SeMet: 2.6 mg g⁻¹), exceeding values commonly reported for commercial Se-enriched yeasts (1-2 mg g⁻¹). Conversion efficiency into organic Se ranged from 53% to 79%, with intermediate Na₂SeO₃ supplementation yielding the most favorable balance between accumulation and transformation. These findings show that both Na₂SeO₃ dose and metabolic pathway strongly influence Se uptake and biotransformation. Cultivation in corn hydrolysate under aerobic conditions not only promoted higher SeMet formation but also reflects conditions relevant to industrial DDGS production. This approach provides a promising strategy to valorize an abundant ethanol coproduct into functional feed with improved selenium bioavailability and reduced risk of toxicity.