Optimization of fermentation conditions and application of extracellular polysaccharide-producing yeast

To explore the feasibility of yeast extracellular polysaccharides (EPS) as an active functional component in cosmetic skin care, a yeast strain preserved in the laboratory was identified using morphological observation and molecular biological techniques. The fermentation conditions for EPS production of the strain were optimized by using the single-factor experiments and response surface method, and the moisturizing, nourishing and repairing effects of the isolated and purified extracellular polysaccharides were determined. The results showed that the strain was identified as Wickerhamomyces anomalus. The optimal culture conditions for EPS production were as follows: the addition of glucose, magnesium sulfate, dipotassium hydrogen phosphate, sodium chloride, ammonium sulfate, and calcium chloride were 44 g/L, 1.7 g/L, 0.3 g/L, 0.7 g/L, 15 g/L, and 0.36 g/L respectively. The inoculum was 4%, and the pH was 6.0. Under these condition, the EPS yield was (1394±25) mg/L. 0.5% extracellular polysaccharides increased the moisture content of the stratum corneum of the skin by 22%, and significantly reduced the SEw value of the skin texture parameter by 9.7% (P<0.05). 0.007% extracellular polysaccharides could significantly promote the proliferation and migration of HaCaT cells, indicating that the EPS produced by W. anomalus had certain skin moisturizing, nourishing and repairing effects.