Optimization of the antifungal metabolite production in Streptomyces libani isolated from northern forests soil in Iran

Document Type : Original Articles


1 Department of Mycology, Faculty of Medical Sciences, Tarbiat Modares University, Tehran 14115-331, Iran

2 Department of Mycology, Pasteur Institute of Iran, Tehran 13164, Iran.


Background and Objectives: Soil bacteria have extreme population diversity among natural sources and are able to produce a wide array of antifungal metabolites. This study aimed toisolate and identifythebioactive metabolite-producing bacteria from forest soils and evaluate their antimicrobial potent against some pathogenic organisms.
Materials and Methods:In this study, soil samples werescreened for antifungal activity against Aspergillus fumigatuson glucose-yeast extract (GY) agar using a visual agar plate assay method. All growing bacteria were examined for antifungal activity, and antagonistic bacteria were identified based on 16S ribosomal RNA sequence analysis. For optimization ofthe production of antifungal bioactive metabolites, inhibitory bacteria were cultured on different culture conditions, including media, pH, temperature, and incubation time.
Results:One-hundred and ten bacterial strains were isolated from the forest soils and fourspecieswith high antifungal activity were identified as Streptomyces libani, Streptomyces angustmyceticus, Bacillus subtilis, andSphingopyxisspp. on the basis of 16s ribosomalRNA sequencing.Dichloromethane extract of the starch casein broth culture filtrate of the S. libani(incubated at 30°C for fivedays) showed strongantifungal activity against A. fumigatus, Aspergillusniger, andAspergillusflavus.
Conclusion:Based on theresults, forest soils contain organisms with antifungal activity and could be considered as a good source for novel antifungal metabolites as effective and safe therapeutics.