Abstract: In order to maximize intracellular ergosterol production in Rhizopus oryzae in liquid-state fermentation, nitrogen and carbon sources and fermentation time were optimized using response surface methodology. Ergosterol was determined by HPLC and the fermentation medium used was based on PDB liquid medium. The effects of carbon and nitrogen source types on ergosterol production were examined. One-factor-at-a-time experiments were conducted to analyze the effects of yeast extract, glucose and fermentation on ergosterol production. The optimum carbon and nitrogen sources were found to be glucose and yeast extract, respectively. The optimum fermentation process was achieved after 9.64 d of culture in a modified PDB liquid medium containing 3 g/L glucose and 5 g/L yeast extract. Under these conditions, the average ergosterol production was 5761.83μg /100 mL of fermentation broth, which was in agreement with the predicted value (5.818.39μg /100 mL of fermentation broth) from the model established and 247.86% higher than before the optimization. Moreover, the ratio of ergosterol to dry cell was 1.60% (100 mL liquid culture medium).

Key words: Rhizopus oryzae ZW017, ergosterol, response surface methodology