The novel bioactive actinobacterial strain GSBNT10 obtained from a Saharan soil, was taxonomically characterized using a polyphasic approach. 16S rRNA gene sequence analysis supported the classification of the isolate within the genus
Streptomyces
indicating it as a novel species. The major metabolite responsible of the bioactivity was purified and structurally characterized as actinomycin D (act-D) by mass spectrometric and nuclear magnetic resonance analyses Plackett-Burman design (PBD) and response surface methodology (RSM) were applied in order to optimize the medium formulation for the production of this bioactive metabolite. By PBD experiments, NaNO
3
, K
2
HPO
4
and initial pH value were selected as significant variables affecting the metabolite production. Central Composite Design (CCD) showed that adjustment of the fermentative medium at pH 8.25, K
2
HPO
4
at 0.2 gL
-1
and NaNO
3
at 3.76 gL
-1
were the values suiting the production of act-D. Moreover, the results obtained by the statistical approach were confirmed by act-D detection using the HPLC equipped with a diode array detector and coupled 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-optimized conditions and data from LC-ESIMS technique efficiently confirmed the forecast from RSM.
Background:
The actinomycetes strains isolated from unexplored ecosystems are a promising
alternative for the biosynthesis of novel antimicrobial compounds. Depending on the interesting antifungal
activity of the studied strain S19, the statistical method seems to be an effective tool for optimizing
the production of anticandidal molecules.
Introduction:
This study was conducted in order to optimize the culture parameters (medium nutrients
concentrations and initial pH value) affecting the production of antifungal metabolites from S.
albidoflavus strain S19 (obtained from wastewater collected in Bejaia region, Algeria) using Response
Surface Methodology (RSM). The best conditions for anti-Candida albicans compounds biosynthesis
were determined.
Methods and Results:
The antimicrobial producer strain S. albidoflavus S19 was identified on the basis
of morphological, chemicals characters and physiological characteristics along with 16S rRNA gene sequencing
analysis.
Response Surface Methodology by Central Composite Design (CCD) was employed to improve the anti-
C. albicans agents production through the optimization of medium parameters. The highest antifungal
activity was obtained by using a mixture of 2g l-1 starch, 4g l-1 yeast extract, 2g l-1 peptone at pH 11.
Conclusion:
The strain S19 isolated from wastewater showed a significant anti-C. albicans activity and
this study revealed the effectiveness of RSM and CCD for increasing bioactive compounds production,
rising the diameter of inhibition zones from 13 to 34 mm.
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