Preparation of Selenium-Enriched Yeast by Re-Using Discarded Saccharomyces cerevisiae from the Beer Industry for Se-Supplemented Fodder Applications

Abstract

Both inorganic and organic selenium (Se) can prevent and treat various diseases caused by Se deficiency. However, organic Se has less toxicity and a higher absorption rate than inorganic Se. In this study, inorganic Se (Na2SeO3) was bio-transformed into Se-enriched discarded beer yeast (Se-enriched DB-yeast) through fermentation accumulation by re-using discarded Saccharomyces cerevisiae from the beer industry for Se-enriched fodder application. Through a single-factor experiment and L9(34)-orthogonal test for optimization of fermentation conditions, the Se content and biomass of Se-enriched DB-yeast were calculated as 14.95 mg/L and 7.3 g/L, respectively, under the optimized condition. The total amino-acid content of Se-enriched DB-yeast was increased by 9.9% compared with that from DB yeast. Additionally, alkaline amino-acid content was increased, whereas acidic amino-acid and sulfur-containing amino-acid contents were decreased. Reducing capacity, hydroxyl radical removal capacity, and sulfhydryl content after treatment with H2O2 of the Se-enriched DB-yeast extracted protein were obviously increased compared with those of the DB-yeast extracted protein. Mouse and genetically improved farmed tilapia (Oreochromis niloticus) (GIFT) bioassays showed that the Se sedimentation of organs and serum indexes after feeding Se-enriched DB-yeast-containing fodder were higher than those of DB-yeast-containing fodder. The half lethal dose (LD50) of Se-enriched DB-yeast (9260.0 mg/kg body weight (BW), 18.97 mg/kg of Se content, non-toxic level) was considerably higher than that of Na2SeO3 (20.0 mg/kg BW, 5.08 mg/kg of Se content, highly toxic level) against mouse. Therefore, Se-enriched yeast prepared by re-using discarded S. cerevisiae from beer industry fermentation accumulation has the potential to be a safe and effective Se-enriched fodder additive.

Effects of Selenium Enrichment on Dough Fermentation Characteristics of Baker’s Yeast

“…The content in commercial Se-enriched yeast is typically 500~2000 μg/g. Commercial yeast is generally S. cerevisiae discarded by the beer industry and processed for Se enrichment [ 27 ]. It has been reported that the enrichment site of Se in yeast is mainly concentrated in the sediment from protoplast fragmentation, and the Se content of this part accounts for more than 75% of the total Se content [ 27 ].…”

“…Commercial yeast is generally S. cerevisiae discarded by the beer industry and processed for Se enrichment [ 27 ]. It has been reported that the enrichment site of Se in yeast is mainly concentrated in the sediment from protoplast fragmentation, and the Se content of this part accounts for more than 75% of the total Se content [ 27 ]. However, brewing materials, alcohol, and other metabolites often form high osmotic pressure in the process of beer production, which to some extent causes the plasmolysis in yeast.…”

A review on selenium-enriched proteins: preparation, purification, identification, bioavailability, bioactivities and application

“…These results were mainly due to the β-structure and irregular curl transition of the protein's turn to the α-helix structure in high Se concentration treatment. 41 Thus, Se treatment could significantly change the secondary and tertiary structures of Oryza sativa glutenin due to the replacement of sulfur on methionine and Cys by Se (Fig. 2).…”

Selenoproteins in Health

“…Se-enriched yeast can be obtained through growing yeast in Se-containing cultures. Commonly, a culture with 30 μg/mL Na 2 SeO 3 can result in Se accumulation in the range of 1200–1400 μg/g dried yeast ( Saccharomyces cerevisiae ), and the inorganic Se can be bio-transformed in yeast to form SePs [ 159 , 160 ].…”