Abstract

A detail research on the control strategies of carbon and nitrogen source was investigated for riboflavin production by Eremothecium ashbyii. The effects of various carbon and nitrogen sources on riboflavin biosynthesis were first employed respectively which revealed that glucose and yeast extract were the optimal medium components for riboflavin fermentation by E. ashbyii. To further improve the productivity of riboflavin, the shake-flask fed-batch cultivation of E. ashbyii was established with glucose and yeast extract, and the results demonstrate that glucose and yeast extract could significantly facilitated cell growth, but the inhibition of riboflavin biosynthesis would be caused by high concentrations of glucose and yeast extract. Based on the results obtained in shake-flask experiments, the strategies of glucose and yeast extract were developed for riboflavin fermentation in 15 L fermenter, in which glucose was fed to maintain its concentration between 0.5 to 0.8 g/100 ml during the whole fermentation process, and 60 g/L of yeast extract was continuously fed at 40 ml/h of rate from 48 to 96 h of fermentation. As a result, maximal riboflavin was 3107.59 mg/L by the fed-batch fermentation in 15 L fermenter, which was 104.77% higher than that obtained in batch fermentation (1517.59 mg/L).

Key words: Eremothecium ashbyii, riboflavin, biosynthesis, cell growth, glucose, yeast extract.