Modeling improved production of the chemotherapeutic polypeptide actinomycin D by a novel Streptomyces sp. strain from a Saharan soil

The novel bioactive actinobacterial strain GSBNT10 obtained from a Saharan soil, was taxonomically charac-terized using a polyphasic approach. 16S rRNA gene sequence analysis supported the classification of the isolatewithin the genusStreptomycesindicating it as a novel species. The major metabolite responsible of the bioactivitywas purified and structurally characterized as actinomycin D (act-D) by mass spectrometric and nuclear magneticresonance analyses Plackett-Burman design (PBD) and response surface methodology (RSM) were applied in orderto optimize the medium formulation for the production of this bioactive metabolite. By PBD experiments, NaNO3,K2HPO4and initial pH value were selected as significant variables affecting the metabolite production. CentralComposite Design (CCD) showed that adjustment of the fermentative medium at pH 8.25, K2HPO4at 0.2 gL-1andNaNO3at 3.76 gL-1were the values suiting the production of act-D. Moreover, the results obtained by the sta-tistical approach were confirmed by act-D detection using the HPLC equipped with a diode array detector andcoupled online with electrospray-mass spectrometry (ESIMS) technique. act-D production was highly stimulated,obtaining a good yield (656.46 mgL-1) which corresponds to a 58.56% increase compared with the non-optimizedconditions and data from LC-ESIMS technique efficiently confirmed the forecast from RSM.