Preparation of Selenium-Enriched Yeast by Re-Using Discarded _Saccharomyces cerevisiae_ from the Beer Industry for Se-Supplemented Fodder Applications  
[PERSON]  
1 School of Chemistry and Chemical Engineering, Zhongkai University of Agricultural Engineering, Guangzhou 510225, China 1, 1,  
metabolism, DNA synthesis, and protection from oxidative damage and infection [3; 4; 5; 6]. There are approximately 0.5 to 1.0 billion people in 40 countries around the world facing potential adverse health impacts because of Se deficiency [7]. Se deficiency is associated with the loss of hair pigment and macrocytosis in intravenously fed children, and is the cause of other human diseases, such as Keshan disease (an endemic cardiomyopathy) and Kashin-Beck disease (a type of osteoarthritis) in China [8; 9]. There is increasing evidence that Se-enriched food can prevent these Se-deficiency diseases and also provide protection against various forms of cancers [1; 5; 10; 11]. Although Se normally enters the food chain from plants as they absorb inorganic Se from the soil and convert it into organic Se, the amount of naturally obtained Se is often insufficient for the optimal growth and development of animals in Se-deficient regions [12]. Therefore, it is essential to supplement human and animal diets with Se-enriched foods [2; 12]. Available Se supplements include inorganic forms (i.e., sodium selenite (Na\({}_{2}\)SeO\({}_{3}\)), sodium hydrogen selenite (NaHSeO\({}_{3}\)), and sodium selenate (Na\({}_{2}\)SeO\({}_{4}\))), which are soluble but poorly bioavailable and potentially toxic. However, through bioconversion, inorganic Se is transformed into organic forms (i.e., Se-enriched yeast (Se-yeast) and the seleno-amino acid, \(\updownarrow\)-selenomethionine (Se-Met)), which have decreased toxicity and elevated absorption rates compared with inorganic Se [13; 14; 15; 16]. Se supplementation produced by microorganisms, especially yeast (i.e., _Saccharomyces cerevisiae_), received much attention in the past decade. Under appropriate conditions, yeast can utilize soluble sugars and organic acids to produce high-protein biomass while accumulating and incorporating large amounts of Se into organic Se-containing compounds, the main form of which is SeMet, which is the best Se source for organisms [13; 17; 18]. Therefore, since the Food and Drug Administration (FDA) approved the use of Se-yeast, an organic source of Se, in poultry diets in 2000, it became one of the most popular sources of Se supplementation in the agriculture and human nutritional supplement industries [15; 19]. Grains, breads, meat, poultry, eggs, cereals, and fish are considered to be the major sources of Se in the diet [5]. In China, genetically improved farmed tilapia (_Oreochromis niloticus_) (GIFT) is a commercially important farmed freshwater fish because of its omnivorous feeding habit, rapid growth rate, and high fillet yield [20]. It can also be considered as an Se carrier in the human diet in some areas of Se deficiency since it is delicious and the total production of tilapia is 1.6 million tons in China, while the total global production is 5.0 million tons [21]. The abundant discarded beer yeast (_S. cerevisiae_) (DB-yeast) originating from the beer industry is a serious source of pollution; however, if DB-yeast is recycled and reused appropriately, it can be converted to a valuable social resource. Generally, DB-yeast from the beer industry is used as a high-protein fodder additive after simple drying. In this study, to improve its utilization value, inorganic Se (Na\({}_{2}\)SeO\({}_{3}\)) was bio-transformed to organic Se (Se-enriched DB-yeast) by re-using DB-yeast. The effects of the fermentation culture conditions on the bioaccumulation of Se in DB-yeast were investigated using a single-factor test and an \(L_{9}\)(3\({}^{4}\))-orthogonal test in Se-enriched media. The as-prepared Se-enriched DB-yeast was further used as the Se-enriched fodder additive for GIFT.