Impact of Ultrasound and Medium Condition on Selenium-Enriched Yeast Production from Sugar Beet Molasses and Date Waste

The growth and Selenium biotransformation of Saccharomyces cerevisiae were optimized by treatment with ultrasonication. Fifteen process variables had a potential influence on the content of organic selenium, including duration of ultrasound, power of ultrasound, inoculum treatment with ultrasound, duty cycle, growth phase, incubation time, shaking rate, different types of carbon sources (molasses and date waste), the concentrations carbon source, inorganic salts concentration (Se, Zn, Mg, and K), nitrogen sources (ammonium chloride and yeast extract) and their concentrations, were screened using Plackett–Burman design to determine the main parameters. Four parameters significant parameters including selenium concentration, degree of brix, ultrasonic power, and duty cycle, were further optimized using Box–Behnken design to achieve optimum fermentation conditions. The results showed that optimization of these parameters could lead to a rise in the content of selenium, resulting in a successful enhancement (2.78-fold) in the accumulation of selenium by S. cerevisia.