Abstract: The biotransformation of iron in Chinese rice wine yeast (Saccharomyces cerevisiae) YS6.2.5 was investigated by tolerance and acclimation tests and culture conditions for iron biotransformation in a shake flask and a fermentor were optimized. The strain had strong iron tolerance and potential for iron biotransformation. The optimal culture conditions in a 500-mL shake flask were determined as follows: an inoculum size of 10%, a medium loading of 40%, and initial pH 4.0 for culture at 28 ℃ for 24 h at a shaking speed of 200 r/min. At the end of the culture period, the biomass and iron content of yeast cells were (14.68 ± 0.37) g/L and (30.15 ± 0.70) mg/g, respectively. The optimal culture conditions in a 50-L fermentor were determined as follows: an inoculum size of 15%, a medium loading of 60%, and addition of Fe2+ at a constant flow rate during the early logarithmic growth phase. After 18 h culture under these conditions, the iron content of yeast cells was as high as 674.79 mg/L, which was 1.52-fold higher than shake flask culture, and the enrichment factor, the percentage of organic iron and conversaion rate were 67.48%, 97.81% and 66.00%, respectivley.

Key words: Chinese rice wine yeast, iron enrichment, biotransformaion, scale-up