An Experimental Design for Production of Selenium-Enriched Yeast

Selenium (Se) enriched yeast, produced by growing of Saccharomyces cerevisiae in Se rich media, is a recognized source of organic food-form of Se. Effects of culture conditions (temperature, fermentation time, initial pH value, shaking speed, as well as time and concentration of Se added to medium) on the bioaccumulation of Se in yeast were investigated by Plackett-Burman design in this paper. Fermentation was carried out at different temperature (28-30°C), initial pH value (4.5-5.8), shaking speed (130-160 rpm), fermentation time (24-48 h), size of inoculums (30-60 g/l), Se concentration (15-25 μg/ml) and time of Se addition (0-9 h). The results showed total Se accumulation and organic Se formation ranges of 107.9 to 287.6 mg/kg and 93.27 to 269.05 mg/kg, respectively. The most suitable conditions for total and organic Se incorporation in yeast were: addition of sodium selenite 25 μg/ml, at 9 h after inoculation, inoculums size of 30 g/l, temperature 28°C, initial pH value 5.8, shaking speed 130 rpm and incubation time of 48 h.