Improvement Of Rifamycin B Producting Strain Amycolatoposis Mediterranei By Rational Screening And Optimalization Of Its Fermentative Technology

Rifamycin B is produced by Amycolatoposis mediterranei. The biosynthesis of rifamycin B was inhibited by the aromatic amino acids, the analogues of aromatic precursor C?N and rifamycin SV. According to the pathway and metabolic regulation of rifamycin B biosynthesis, improvement of Amycolatoposis mediterranei XC1-97 by rational screening was performed to select the mutants which could grow well on the medium with .the concentration of 0.1% trp, 0.5% trp, 0.1% ANA and 0.1% rifamycin SV in order to alleviate the inhibition caused by trp, ANA and rifamycin SV. By above methods, a mutant A. mediterranei XC7-2 was obtained. The rifamycin B potency of A. mediterranei XC7-2 reached 12000u/ml, which was 1.85 times higher than that of original strain XC1-97.Fermentation of A. mediterranei XC7-2 in 15L fermentor was performed with the original technology, and the results showed that the potency of rifamycin B was almost the same as the original strain. In order to increase the productivity of A. mediterranei XC7-2 in 15L fermentor, the fermentative technology was studied.Fermentation of A. mediterranei XC7-2 was carried in shaking flask and 151 fermentor. The influence of the cultural temperature, dissolved oxygen, barbitone, KH2P04 concentration, precursors and the feeding methods on rifamycin B fermentation was studied. The results indicated that the potency of rifamycin B was increased evidently on the condition of the cultural temperature 27℃, the dissolved oxygen level over 25% and (NH4)2SO4 in place of partial KN03, KH2P04 concentration 0.05%, the precursor 0.3-0.5% and with continuous feeding method, and that barbitone has no influence on rifamycin B biosynthesis. The optimal technology was used in 60m3 fermentor industrially, and it made the productivity increased doubly, reaching more than 22000u/ml.