Culture medium optimization and active compounds investigation of an anti-quorum sensing marine-derived actinomycete Streptomyces chumphonensis HN2-56

Quorum sensing inhibitors (QSIs) can inhibit the quorum sensing regulated physiological functions of bacteria and might be useful in drug-resistant bacterial infection therapy. The culture medium of a mangrove derived actinobacterium Streptomyces chumphonensis HN2-56, which exhibiting higher anti-quorum sensing activity, was optimized in this study. The results showed that the GS medium was the most favourable medium for the bioactivity of HN2-56 and that the content of soluble starch in the GS medium had a significant impact on the yield of metabolites. By culturing under the optimized condition (soluble starch 40 g/L, KNO3 4 g/L, salinity of 0 and pH 6.5), both metabolites production and anti-quorum sensing activity of HN2-56 against the purple pigment (violacein) production of Chromobacterium violaceum 12472 were significantly increased (41.8% and 177.9%, respectively). Five pure compounds were obtained from the extract of HN2-56 and identified as 2,2-[bis-4-(2,3-dihydroxypropane) phenyl] propane (1), bisphenol A (2), 5-(2-methylphenyl)-4-pentenoic acid (3), 3-methyl-1H-indole-2-carboxylate (4) and dibutyl phthalate (5). Among them, compounds 2 and 3 showed anti-quorum sensing activity against C. violaceum 12472 and anti-biofilm activity against Staphylococcus aureus 43300. These findings indicated that S. chumphonensis HN2-56 should be a promising candidate for QSIs with potential anti-quorum sensing application. Although BPA was detected in the HN2-56 extract, experimental contamination could not be excluded because of the ubiquitous presence of BPA in plasticware and laboratory reagents.