Enhanced production of Rifamycins B and SV by medium supplementation with Vermiculite

Rifamycins are broad spectrum and important antibiotics used in the treatment of pathogenic diseases. They are generally produced by the fermentative cultivation of Amycolatopsis mediterranei, using submerged cultivation system. The medium composition greatly influences the antibiotic production. Trace elements are one of the major factors need to be optimized to enhance the production of rifamycins. In the present work, we investigated the possible improvement of rifamycins B and SV production through the addition of vermiculite (dehydrated magnesium-aluminum-ion silicate) as a cheap and affordable source of trace elements. The obtained results showed that the addition of 20 g/L vermiculite gave the highest volumetric production of rifamycins B and SV (767.5 and 1265 mg/L for Rif B and SV, respectively). Moreover, addition of vermiculite at the beginning of the cultivation resulted in the highest volumetric productivities in comparison to control cultivation (770 and 1305 mg/mL of rifamycin B and SV, respectively). Comparative growth curve kinetics between vermiculite-supplemented medium and vermiculite free medium demonstrated that vermiculite significantly enhanced cell growth, cell growth rate, glucose consumption rate, as well as the production rates of both rifamycins B and SV compared to cultivation without vermiculite. In addition, vermiculite supplementation increased both maximal volumetric productivity and production rates increased by about 32 and 52% for rifamycin B and SV, respectively, as compared to vermiculitefree cultivation.