ORIGINAL ARTICLE Metabolite profile of marine-derived endophytic Streptomyces sundarbansensis WR1L1S8 by liquid chromatography–mass spectrometry and evaluation of culture conditions on antibacterial activity and mycelial growth I. Djinni 1,2 , A. Defant 1 , M. Kecha 2 and I. Mancini 1 1 Bioorganic Chemistry Laboratory, Department of Physics, University of Trento, Povo, Italy 2 Laboratory of Applied Microbiology, Faculty of Nature Science and Life, University of Bejaia, Targa Ouzemmour, Bejaia, Algeria Keywords actinomycetes, algae, antimicrobials, LC-MS analysis, polyketide. Correspondence Ines Mancini, Bioorganic Chemistry Labora- tory, Department of Physics, University of Trento, via Sommarive 14-38123, Povo, Trento, Italy. E-mail: ines.mancini@unitn.it 2013/1461: received 19 July 2013, revised 26 September 2013 and accepted 1 October 2013 doi:10.1111/jam.12360 Abstract Aims: This study was designed to investigate whether culture conditions (media, seawater concentration and pH) could lead Streptomyces sundarbansensis strain (isolated from marine brown algae Fucus sp. collected from Algerian coastline) to produce bioactive secondary metabolites. The most favourable condition for the production of anti-MRSA compound 1 [2-hydroxy-5-((6-hydroxy-4-oxo-4H- pyran-2-yl)methyl)-2-propylchroman-4-one] was determined. Methods and Results: The profile of metabolites present in the crude extracts was carried out by HPLC analysis equipped with a diode array detector evaporative light scattering detection (DAD-ELSD) or online coupled to electrospray ionization–mass spectrometry (ESI-MS). Compound 1 was the most abundant secondary metabolite by culturing the strains on starch casein agar (SCA) medium in freshwater or 50% seawater at pH 7 or 9 using agar-state fermentation method. Conclusions: The study has shown the efficiency of HPLC/ESI-MS technique in the analysis of polyketides produced by the strain under investigation. It was possible to establish the best culture conditions for obtaining the most bioactive compound 1, previously isolated by the same strain. Significance and Impact of the Study: Marine algae–actinobacteria associations are a particularly promising renewable system for the production of new antibacterial metabolites. Based on the promising bioactivity of the chemically characterized compound 1, the analytical methodology here applied has resulted as an effective approach for establishing its optimized production. Introduction Thanks to their ability to produce numerous and diverse bioactive natural products, marine micro-organisms, especially bacteria belonging to the Actinomycetales order, are attracting much more attention as stimulated by the need of novel antibiotics for multiresistant pathogenic strains and of antitumour agents. This takes advantage from the diversity of marine environment which has exerted a driving force on bacteria selection leading to new adaptive strategies and to the synthesis of novel bio- active metabolites (Jensen and Fenical 1996; De Carvalho and Pedro 2010). In our recent screening for bioactive metabolites from marine-derived actinomycetales, Streptomyces sp. WR1L1S8 strain was selected among twenty-two strains isolated from a marine algae collected in Bejaia coastline, North East of Algeria. This strain produced a new polyketide 1 [2-hydroxy-5-((6-hydroxy-4-oxo-4H-pyran-2-yl)methyl)-2- propylchroman-4-one] as well as three known compounds Journal of Applied Microbiology 116, 39--50 © 2013 The Society for Applied Microbiology 39 Journal of Applied Microbiology ISSN 1364-5072