Abstract
Se-rich yeast within animal feeds is much more effective than additions of inorganic Se in increasing the concentration of Se in eggs, milk and meat. This study was conducted in order to select mutant Saccharomyces cerevisiae which produce higher levels of organic selenium (Se) and to improve the productivity of this Se-rich yeast by optimization of the culturing condition. Among 13 ATCC strains of S. cerevisiae, ATCC 560 showed a higher tolerance towards Se, exhibiting a total Se uptake rate of 6.69 mg/l. The mutant S. cerevisiae 6M, which is an ATCC 560 derivative developed through UV mutagenesis, showed about 20% increased Se production rates (8.0 mg/l). Optimal culturing conditions were determined, in terms of the timing and addition of inorganic Se, initial pH, and overall culturing time. The optimal concentration of inorganic Se was determined to be 125 ppm, the optimum time for the addition of which was determined to be at the start of incubation. The optimal initial pH of the medium and culturing time was 6.0 and 9 h, respectively. Under these conditions, S. cerevisiae 6M showed a total Se production of 10.87 mg/l, a 63% increase compared to that of with ATCC 560 under normal culture conditions. Key words: Saccharomyces cerevisiae, organic selenium, UV mutagenesis, culture condition .
Highlights
Organically-bound Se is essential for the growth of animals and humans alike
This study was conducted in order to select mutant Saccharomyces cerevisiae which produce higher levels of organic selenium (Se) and to improve the productivity of this Se-rich yeast by optimization of the culturing condition
Among 13 ATCC strains of S. cerevisiae, ATCC 560 showed a higher tolerance towards Se, exhibiting a total Se uptake rate of 6.69 mg/l
Summary
Organically-bound Se is essential for the growth of animals and humans alike. Se is an important element found in selenoproteins and enzymes with various physiological functions, such as antioxidant defense, inflammation reduction, thyroid hormone production, DNA synthesis, fertility, and reproduction (Rayman, 2000). Meat, chicken, fish, and eggs are protein-rich foods, containing high levels of Se (Klapec et al, 2004; McNaughton and Marks, 2002; Pappa et al, 2006; Sirichakwal et al, 2005). Organic Se supplements, such as those sourced from Se yeast, are much more effective than those of inorganic Se in increasing the concentration of Se in egg, milk, blood, and plasma (Fisinin et al, 2008; Ortman and Pehrson, 1999; Slavik et al, 2008). Organic Se is a highly bioavailable form of Se for chickens and other livestock, and provides a greater level of antioxidant protection than inorganic Se (Mahan, 1999; Mahmoud and Edens, 2003)
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