Abstract

A systematic approach to process optimization for production of rifamycin B was applied to a strain of Amycolatopsis mediterranei. Examination of the growth revealed 6 different morphologically distinct colonies on Bennett’s agar medium. Rifamycin B production in shake flasks by the six different colony types ranged between 0.5 and 1.2 g/l. There was a clear correlation between the colony morphology and rifamycin B productivity. The highest yield of rifamycin B (1.03-1.2 g/l) was obtained by using the orange-red colored colonies, rosette shaped, devoid of hollow center and 2-3 mm in diameter. Variability in colony morphology, however, remained and the appropriate colonies had to be picked up for preparing the inoculum of each experiment. Addition of yeast extract to the fermentation medium at different times increased rifamycin B production. The highest antibiotic production was obtained upon the addition of 0.1% yeast extract after 2 days of incubation, where the yield increased from 1.15 to 1.95 g/l (70%). The use of 1.8% KNO₃ in the fermentation medium, instead of  0.96% (NH₄)₂SO_4,  markedly increased  rifamycin B production from 1.15  to 2.92  g/l (154%). It was also observed, upon microscopical examination, that KNO₃ decreased branching and fragmentation of the mycelia in the fermentation medium.

Key words: Rifamycin B, fermentation, biotechnology, Amycolatopsis mediterranei,strain selection.