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Spiramycin is a multicomponent antibiotic, and different components have different antibacterial activities. InStreptomyces spiramyceticus16-10-2, spiramycin II and spiramycin III (SPMII and SPMIII) are the main components, while spiramycin I (SPMI) needs to be controlled below 12%. Based on this, the influences of Al3+on total spiramycin titer and components were investigated in this work. Those experiments were mainly performed in 15 L fermentor and Al3+made a great improvement in spiramycin titer. The optimal adding concentration and adding time of Al3+were 0.32 g/L at 12 hr. Under this condition, spiramycin titer was increased by 19.51% compared with the control. Moreover, the percentage of SPMII and SPMIII was increased by 7.14%. At the same time, the time of mycelia autolysis was lengthened. In addition, the specific activities of acetyl-CoA synthetase, acetate kinase, acetylphosphotransferase, and acylating enzyme were much higher than those of control. The content of acetic acid and succinic acid was beyond 3 and 4.5 times than that of control, respectively. [ABSTRACT FROM PUBLISHER]

Abstract: Tilmicosin is a semisynthetic macrolide antibiotic derived from tylosin. The disruption of tylCV gene from tylosin producer—Streptomyces fradiae would result in the accumulation of desmycosin, the direct precursor of tilmicosin. TylCV gene disruption cassette was constructed by fusion PCR. The tylCV replacement strain of S. fradiae was obtained through intergeneric conjugation between S. fradiae and E. coli. The antibiotic resistance cassette is flanked by yeast FLP recombinase target sequences for removal of the antibiotic resistance and oriTRK2 to generate unmarked, nonpolar mutation. After optimization of the culture conditions, the yield of desmycosin reached 7.3gl−l in 5l jar fermentor, which could be scale-up for industrial fermentation to produce large amount of desmycosin for semisynthesis of tilmicosin directly. [Copyright &y& Elsevier]