Optimization of natural fermentative medium for selenium-enriched yeast by d-optimal mixture design

Natural fermentative medium for selenium-enriched yeast (Saccharomyces cerevisiae) culture was investigated using response surface methodology (RSM). The medium with a concentration of 15 μg/mL Na₂SeO₃, contained various ratios of juices from germinated brown rice (0.40 ∼ 0.80, 12 Brix), beerwort (0.10 ∼ 0.50, 12 Brix) and soybean sprout (0.10 ∼ 0.50, 12 Brix), which were optimized by applying d-optimal mixture design (DMD). The effects of their ratios on biomass yield and total selenium (Se) yield were analyzed. The results showed that when the mixed ratio of the components was 4:4:2 (v:v:v), the maximum value of biomass yield and total Se yield were 8.5 g/L and 3.53 mg/L, respectively. Verification experimental trials were performed for validating the models, and it indicated that the above mixture of these natural materials can be used as proper medium for the growth of selenium-enriched yeast and accumulation of Se.