Studies on the breeding by ion implantation and cultivation of mycophenolic acid producing strain
离子注入选育霉酚酸高产菌株及其发酵条件研究

Mycophenolic acid is produced by aerobic fermentation of several Penicillium species. It has a broad spectrum of activity like antitumor activity, antiviral, anti-psoriatic, immunosuppressive and anti-inflammatory activity. It also exhibits antibacterial and antifungal activities. The immunosuppressive effect of MPA has been important in treatment of organ rejection after organ transplant surgery. There is a continuous need to find improved process for efficiently obtaining superior MPA producing mutants. In recent years, the ion implantation technique has been widely applied in many fields and has been drawn morn concern. However there is no report in the field of mutational breeding of MPA producing strain. Penicillium brevicompactum M-51 was derived from MPA producing strain F-663 by varied mutational methods including U.V. and microwave irradiation. In the process of increasing the production of MPA from P. brevicompactum M-51, a mutant strain M-163 was obtained by means of N+ ion implantation. An decline-increase-decline tendency of strain survival rates was observed when the strain was implanted by N+ ion with dose from 20 2.6 x 10(13) ions/cm2 to 180 x 2.6 x 10(13) ions/cm2 under implantation energy 15 keV. It apparently appeared "saddle shape". And under the implantation dose of 140 x 2.6 x 10(13) ions/cm2, the variation rate and the positive variation rate of the strain had reached the highest values 88.9% and 63.4%, respectively. The HPLC results showed that MPA yield of P. brevicompactum M-163 was improved by 30.1%, and its productivity was rather stable through successive transfer of cultures. The effect of seed growth time on yield of MPA was studied, and the best seed age was 24h after incubation. In the mean time, the fermentative condition of M-163 was studied through orthogonal design. The major ingredients being investigated included carbon and nitrogen sources. Finally the optimized fermentation medium was obtained. The yield of MPA reached 2819g/mL in the optimized submerged fermentation progress. In conclusion, N+ ion implantation had been proven to be effective for mutational breeding of P. brevicompactum M-51. By means of N+ ion implantation and optimizing the fermentative condition, the yield of MPA was increased by 20.2 times than the wild-type stain F-663.