Cyclo(L-Pro-L-Tyr) from Streptomyces sp. 150: Exploiting in vitro Potential in Controlling Foodborne Pathogens and Phytopathogens

Background: In the prokaryotic unicellular bacteria, Streptomyces species are the most frequent producers of bioactive secondary metabolites. Our continuous quest for new antibiotics from Actinomycetes genera put us forward for isolation of a strain Streptomyces sp. 150 from the soil samples collected at the Daegu University premises in Korea. Objective: The aims of this study was to isolate and identify bioactive compounds from the isolated microorganism and assess the efficacy of the compounds in controlling foodborne pathogens and phytopathogens. Methods: The isolated bacterium was characterized by the taxonomic analyses and a compound was isolated from the fermentation broth by applying different chromatographic techniques e.g. column chromatography, TLC and PTLC. The structure of the compound was established by UV, IR, 1H-NMR and 13C-NMR spectral data analyses. The antibacterial and antifungal efficacy of the compound was assessed by disc diffusion assay, poisoned food technique, MIC determination and SEM analysis. Results: Different chromatographic techniques resulted in isolation and purification of a secondary metabolite from the fermentation broth of Streptomyces sp. 150. The analyses of the spectroscopic data identified the compound as cyclo(L-Pro-L-Tyr). The compound exhibited potential efficacy in controlling all the seven foodborne pathogenic bacteria with corresponding inhibition zone and minimum inhibitory concentration (MIC) ranging from 15.1 to 20.1 mm and 15.6 to 62.5 μg/mL respectively, and tested phytopathogenic fungi with mycelium growth inhibition varying from 57.1 to 68.5% and MIC from 125 to 250 μg/mL. Moreover, in scanning electron microscopy, morphological changes in Listeria monocytogenes ATCC 19166 at MIC dose of compound was observed. Conclusion: This study demonstrated the possibility to use the compound cyclo(L-Pro-L-Tyr) in food and agrochemical industries to control foodborne pathogens and phytopathogens.