Study On The Fumigaclavine C Fermentation Process

Fumigaclavine C (FC), an ergot alkaloid derivative isolated from cultures of a marine-derived fungus Aspergillus fumigatus, was proven to possess comparable anti-inflammation and immunosuppression activities with cyclosporin A. However, its wide application has been limited by the low production from the original cultures. Therefore, efforts devoted into the enhancement of FC production are required considering its further application. In the present work, the effects of different strategies on the fermentation process were studied in order to provide useful information for developing efficient fermentation process.Since FC is a conidiation associated ergot alkaloids, a two-stage culture process which combining shake culture with static culture was proposed to enhance the production of FC. The conidiation of A. fumigatus were significantly promoted using this two-stage process. And the relationship between FC biosynthesis and conidiation was also revealed. Afterwards, the Box-Behnken design (BBD) was used for further optimization of the two-stage fermentation process. With the optimization, the maximum FC production was 62.7 mg/L when shake temperature was kept at 28 ℃ with shake time of 4.5 days and static time of 8 days.Based on the two-stage cultivation, we further explored the effects of ultrasonic on the FC fermentation process. It revealed that the ultrasonic treatment could enhance the conidiation and FC production. The optimum ultrasonication conditions consisted of exposing cultures (at 12 h of growth phase) to 10-min repeated irradiation (4 times) with a 24-h interval at the fixed power. Under this condition, FC production reached 118.1 mg/L, which was 89% higher than the control. Further study indicated that ultrasonic treatment could enhance the FC biosynthesis by upgrading both the utilization efficiency of substrates and the metabolic rate of A. fumigatusIn order to reduce the cost of FC production, the fermentation medium was re-screened and the technical feasibility of using molasses as a low-cost substrate was studied as well. With molasses supplementation, the conidiation and FC production was greatly enhanced. The metabolic rate and the HMGR activity were up-regulated as well. The optimal FC production increased to 226.9 mg/L with the presence of 100 g/L molasses, which was the highest value than ever report. Therefore, molasses was confirmed as a cost-effective ingredient for FC production by two-stage culture of A. fumigatus.The fermentation process in shake-flask scale was not sufficient for large-scale production of FC. Efforts devoted into the reproduction of the process bioreactor system are required considering its further application. In this work, a two-stage bioreactor system was proposed to produce FC by combining a stirred-tank reactor and a static reactor. By using the scale-up strategy, similar impeller linear velocity together with gas-liquid interfacial area, the two-stage process was successfully reproduced in both small and large scale bioreactor systems (the FC production were over 200 mg/L). The information obtained in this work would be helpful to the large-scale production of FC and other useful conidia associated secondary metabolites.