Seed Stage Manipulation as a Tool for Improving Rapamycin Production by Streptomyces hygroscopicus ATCC 29253

Adopting standard fermentation process, the effect of different seed culture preparations on rapamycin production by Streptomyces hygroscopicus ATCC 29253 was realized. Concerning the type of cultivation medium, starch casein broth adjusted at pH 7 or 8 afforded the best formulation for seed culture. Rising pH to 9 was accompanied with sharp depletion in rapamycin titer. It was also found that 5 days old inoculum was the best suited. Four-fold increase in rapamycin yield was attained by rising cell count in seed culture from 25.8x10 2 to 25.8x10 6 c.f.u./flask. The study proposed growth morphology, instead of growth quantity, to be the proper approach for understanding the role of cell count in controlling microbial activity of seed culture. Growth morphology at different cell counts was depicted and its correlation to microbial activity was postulated. Effect of inoculum size has been also clarified where the highest rapamycin yield was attained at inoculum size of 6%. A typical fermentation with the developed optimal seed culture revealed that rapamycin yield was accelerated from 39.53 to 89.20 mg/l together with reduction of the incubation period to five days.