Strain screening and sodium lactate effect on spiramycin production in Streptomyces spiramyceticus

Strain improvement and addition of sodium lactate to fermentation medium to enhance the productivity of spiramycin were performed. Of the sodium lactate tolerant mutants that were screened, one mutant, Streptomyces spiramyceticus 16 - 10 - 12 , produced 23 % more spiramycin than the original strain, Streptomyces spiramyceticus 5 - 1 . The effect of sodium lactate on spiramycin production with S. spiramyceticus 16 - 10 - 12 was studied. The titer was improved by 16.9 % with the addition of 15 g L −1 sodium lactate in the fermentation medium at the beginning. The results from using the new process in a 15 L bioreactor showed that there were more precursors in fermentation broth with a sodium lactate tolerant mutant, and that these precursors were used more than with the original strain. After adding sodium lactate, the titer was increased by 23.4 %, because the flux to TCA circulation was increased, more precursors had been produced and the activities of Acyl-CoA synthetases, Acylphosphotransferases and Acylkinases in synthesis phase were also increased.