Antibacterial Polyketides from the Marine Alga-Derived Endophitic Streptomyces sundarbansensis: A Study on Hydroxypyrone Tautomerism

Polyketide 13 [=2-hydroxy-5-((6-hydroxy-4-oxo-4H-pyran-2-yl)methyl)-2- propylchroman-4-one] and three related known compounds 7, 9 and 11 were obtained and structurally characterized from Streptomyces sundarbansensis strain, an endophytic actinomycete isolated from the Algerian marine brown algae Fucus sp. Compound 13 was obtained as the major metabolite from optimized culture conditions, by using Agar state fermentation. Due to tautomeric equilibrium, 13 in CD3OD solution was able to incorporate five deuterium atoms, as deduced by NMR and ESI-MS/MS analysis. The 2-hydroxy-γ-pyrone form was established for these metabolites based on the comparison of their experimental IR spectra with the DFT calculated ones, for both the corresponding 4-hydroxy-α-pyrone and 2-hydroxy-γ-pyrone forms. During antibacterial evaluation, compound 13 stood out as the most active of the series, showing a selective activity against the gram positive pathogenic methicillin-resistant S. aureus (MRSA, MIC = 6 μΜ), with a bacteriostatic effect

Solid State Fermentation Based Olive Pomace Using Streptomyces Strains: A Preliminary Study

International audienc

Integrated Metabolomic, Molecular Networking, and Genome Mining Analyses Uncover Novel Angucyclines From Streptomyces sp. RO-S4 Strain Isolated From Bejaia Bay, Algeria

International audienceMulti-omic approaches have recently made big strides toward the effective exploration of microorganisms, accelerating the discovery of new bioactive compounds. We combined metabolomic, molecular networking, and genomic-based approaches to investigate the metabolic potential of the Streptomyces sp. RO-S4 strain isolated from the polluted waters of Bejaia Bay in Algeria. Antagonistic assays against methicillin-resistant Staphylococcus aureus with RO-S4 organic extracts showed an inhibition zone of 20 mm by using the agar diffusion method, and its minimum inhibitory concentration was 16 μg/ml. A molecular network was created using GNPS and annotated through the comparison of MS/MS spectra against several databases. The predominant compounds in the RO-S4 extract belonged to the angucycline family. Three compounds were annotated as known metabolites, while all the others were putatively new to Science. Notably, all compounds had fridamycin-like aglycones, and several of them had a lactonized D ring analogous to that of urdamycin L. The whole genome of Streptomyces RO-S4 was sequenced to identify the biosynthetic gene cluster (BGC) linked to these angucyclines, which yielded a draft genome of 7,497,846 bp with 72.4% G+C content. Subsequently, a genome mining analysis revealed 19 putative biosynthetic gene clusters, including a grincamycin-like BGC with high similarity to that of Streptomyces sp. CZN-748, that was previously reported to also produce mostly open fridamycin-like aglycones. As the ring-opening process leading to these compounds is still not defined, we performed a comparative analysis with other angucycline BGCs and advanced some hypotheses to explain the ring-opening and lactonization, possibly linked to the uncoupling between the activity of GcnE and GcnM homologs in the RO-S4 strain. The combination of metabolomic and genomic approaches greatly improved the interpretation of the metabolic potential of the RO-S4 strain

Statistical Medium Optimization for the Production of Anti-Methicillin-Resistant <i>Staphylococcus aureus</i> Metabolites from a Coal-Mining-Soil-Derived <i>Streptomyces rochei</i> CMB47

The development of novel antibacterial drugs needs urgent action due to the global emergence of antibiotic resistance. In this challenge, actinobacterial strains from arid ecosystems are proving to be promising sources of new bioactive metabolites. The identified Streptomyces rochei strain CMB47, isolated from coal mine Saharan soil, provided an ethyl acetate extract which tested against a series of pathogens. It displayed a minimum inhibitory concentration of 3 concentrations, incubation time and the initial pH value, reaching the inhibition zone diameter of 20 mm, close to the experimental value, after validation of the model. A bioassay-guided fractionation of the crude extract provided the most active fractions, which were analyzed by HPLC equipped with a photodiode array detector and coupled online with an electrospray mass spectrometer (HPLC-DAD/ESI-MS), obtaining preliminary indications on the molecular structures of the metabolites. These results support the potential interest in further investigations into the purification and full characterization of the metabolites responsible for the biological activity observed so far

Solid State Fermentation Based Olive Pomace Using Streptomyces Strains: A Preliminary Study

International audienc

Optimization and partial characterization of endoglucanase produced by Streptomyces sp. B-PNG23

Streptomyces sp. B-PNG23 was selected as a promising cellulolytic strain and tested for its ability to produce cellulases from agroindustrial residues. A pH value of 7 and temperature of 28°C were found to be optimal for maximum enzyme production. The highest endoglucanase activity was obtained in a medium comprised of wheat bran (2 g/l), yeast extract (2 g/l), NaCl (2 g/l), NH4Cl (2.5 g/l), and (0.4 g/l) of MgSO4. The enzyme was active at a broad range of pH (5-8) and temperatures (40-70°C). The optimum pH and temperature were 6 and 50°C, respectively. In the presence of metal ions Mn2+, Cu2+ and NH4 + the activity of the enzyme increased significantly. The enzyme retained 50% of its activity after heating at 50°C for 6 h. This enzyme could be considered as a thermotolerant biocatalyst that could be utilized in biotechnological applications

Selective Isolation and Screening of Actinobacteria Strains Producing Lignocellulolytic Enzymes Using Olive Pomace as Substrate

International audienceBackground: Olive pomace, as the main by-product of the olive oil industry, is recently recycled as fermentation substrate for enzyme production. Objectives: Actinobacteria isolates were separated from an Algerian soil under olive pomace cultivation and were evaluated for their lignocellulolytic enzymes production.Materials and Methods: Isolates of Actinobacteria were separated from soils around oil mills using four isolation media, among them three were enriched by olive pomace. The isolates were screened for their cellulolytic, xylanolytic and ligninolytic activities. Isolates with potential of producing lignocellulose-degrading enzymes were selected under submerged fermentation based olive pomace.Results: Ninety isolates of Actinobacteria were separated from soil samples. M3 medium (raw pomace autoclaved alone) was the best isolation medium (68 strains), whereas, the soil from oil mill with continuous system (S1) led to separation of 52 strains. Among the 90 isolates, 82 were shown promising enzyme activity, 19 isolates were presented the largest zone diameter (< 30 mm). S1M3I and S1M3II isolates were exhibited the highest values.Conclusions: Olive pomace with medium low cost and high titers of enzymes can be valorized by culture of Actinobacteria to produce lignocellulolytic enzymes for industrial applications

Optimization and partial characterization of endoglucanase produced by Streptomyces SP B-PNG23

Streptomyces sp. B-PNG23 was selected as a promising cellulolytic strain and tested for its ability to produce cellulases from agroindustrial residues. A pH value of 7 and temperature of 28 C were found to be optimal for maximum enzyme production. The highest endoglucanase activity was obtained in a medium comprised of wheat bran (2 g/l), yeast extract (2 g/l), NaCl (2 g/l), NH4Cl (2.5 g/l), and (0.4 g/l) of MgSO4. The enzyme was active at a broad range of pH (5-8) and temperatures (40-70 degrees C). The optimum pH and temperature were 6 and 50 degrees C, respectively. In the presence of metal ions Mn2+, Cu2+ and NH4+ the activity of the enzyme increased significantly. The enzyme retained 50% of its activity after heating at 50 degrees C for 6 h. This enzyme could be considered as a thermotolerant biocatalyst that could be utilized in biotechnological applications

Isolation and Screening of Fungal Culture Isolated From Algerian Soil for the Production of Cellulase and Xylanase

Lignocellulolytic enzymes constitute a very large group of extracellular proteins secreting by fungi who is ecologically involved in the degradation of a variety of complex materials, a property that is attributed to a battery of enzymes produced by these microorganisms like cellulases and xylanases who are of significant industrial value and relevance. Forty fungal isolated from rich soil in organic matter were screened for lignocellulolytic enzymes production, its organized on the basis of their hydrolytic potential of cellulose and xylan. The isolates strains presented enzymatic activity which was ranked as follows: cellulolytic (56%), xylanolytic (44%). Some selected strains that produce high levels of enzymes (cellulase, xylanase) grown in submerged fermentation (SmF) and were quantitatively evaluated. The fermentation experiments were carried out in shake flasks. The highest CMCase (5,10 IU/ml) and xylanase (98,25 IU/ml) activities were obtained from Trichoderma sp strain Mtr6 isolate. Keywords: Fungi, Trichoderma sp, lignocellulolytic enzymes, soil, screening, organic matter