[Improving ergosterol production from molasses by Saccharomyces cerevisiae].

Ergosterol is an economically important metabolite produced by yeast. To improve the production of ergosterol by Saccharomyces cerevisiae YEH56 (pHXA42) from molasses, a cheap and regenerative material, different strategies were applied. First, Plackett-Burman design and central composite design were applied to screen the significant factors in fermentation medium using ergosterol yield (g/L) as the response value. Ergosterol yield reached 371.56 mg/L by using the optimal fermentation medium in shake-flask culture (total sugar in molasses 40 g/L, KH2PO4 1 g/L, K2HPO4 1.86 g/L, CuSO4 x 5H2O 17.5 mg/L, FeSO4 x 7H2O 13.9 mg/L, MgSO4 x 5H2O 12.3 mg/L, corn steep liquor 10 mL/L), which was increased by 29.5% compared with the initial culture. Second, ergosterol yield was increased by 62.1% using a pH-control strategy in a 5-L bioreactor. Third, ergosterol production was improved further by using molasses feeding strategy. After 38 h fermentation, ergosterol yield reached 1 953.85 mg/L, which was 3.2 times of that in batch fermentation. Meanwhile, ergosterol production rate was increased by 42.7% compared with that in the batch culture.