Response Surface Methodology Used for Investigating Soluble Organic Selenium Accumulation in Yeasts

Selenium-enriched yeasts were usually regarded as an ideal organic selenium source. The study investigated the Soluble Organic Selenium (SOS) accumulation in three species of yeasts: Saccharomyces cerevisiae, Candida rugosa and Candida utilis. The effects of main factors on organic selenium accumulation were evaluated. The Response Surface Methodology (RSM) and Central Composite Design (CCD) were applied to optimize the dosage of main factors in fermentation medium. SOS content in the dry cells of C. utilis (1.31±0.065 mg/g) was higher than that of S. cerevisiae (1.20±0.057 mg/g) and C. rugosa (0.68±0.033 mg/g). However, as far as the productivity of per unit volume of broth was concerned, Candida rugosa also accumulated the most SOS (4.81±0.18 mg/L) among the three species of yeasts. Higher content of SOS in yeasts inhibited the cell growth and led to decrease of SOS per unit volume during yeasts fermentation. Perhaps, yeasts with lower content of SOS have the advantage of SOS accumulation per unit volume broth accumulation.