Metal coordinating-induced self-assembly of cyclic lipopeptides into high-performance antimicrobial supramolecules.

This study designed a green hydrothermally-chelating approach to generate robust antimicrobial complexes via metal-coordinated supramolecular self-assembly of cyclic lipopeptides (CLs). The metal ion (Ca2+ and Zn2+)-coordinated CL (Ca/CL or Zn/CL complex; 1 mg/mL) demonstrated potent antibacterial activity against fungi (A. niger) and bacteria (E. coli and S. aureus) respectively, and in particular, completely suppressed the microbial resistance. Further physicochemical and spectal analysis showed that this coordination approach led to CL with enhanced hydrophobic and intermolecular electrostatic interactions, forming ß-sheet-rich secondary structures allowing the complexes easily contact with and destroy the membrane of microorganisms. Practical application experiments validated that the Ca/CL and Zn/CL complexes strongly avoided table grape and fresh tomato from the contamination of pathogen. The findings of this study laid foundation for the utilization of metal ions to improve the biological activity of natural antimicrobial peptides.

Activation of persulfate by nanoscale zero-valent iron loaded porous graphitized biochar for the removal of 17ß-estradiol: Synthesis, performance and mechanism.

In this work, the porosity, graphitization and iron doping of biochar were realized simultaneously by the pyrolysis of biomass and potassium ferrate (K2FeO4), then the iron-doped graphitized biochar was reduced to synthesize nanoscale zero-valent iron loaded porous graphitized biochar (nZVI/PGBC). 17ß-estradiol (E2) is an environmental endocrine disruptor that can cause great harm to the environment in small doses. Experiments illustrated that nZVI/PGBC (100 mg/L) could completely remove E2 (3 mg/L) within 45 min by activating sodium persulfate (PS, 400 mg/L). The E2 removal efficiency of nZVI/PGBC was obviously superior to that of pristine biochar (BC), iron-doped graphitized biochar (Fe/GBC), nanoscale zero-valent iron (nZVI) and porous graphitized biochar (PGBC). The removal efficiency could be affected by reaction conditions, including reaction temperature, acidity, dosage of catalyst and oxidant and water matrix. Quenching experiments and electron spin resonance (ESR) demonstrated that SO4-· and HO were both responsible for E2 degradation. This study indicated that Fe0 and Fe2+ were the main catalytic active substances, while the catalytic ability of PGBC was not obvious. The reaction mechanism was proposed, that is, PS was activated by electrons provided by the redox reaction between Fe2+ and Fe3+, and PGBC acted as the carrier of nZVI, the adsorbent of E2 and the mediator of electron-transfer. This study demonstrates that nZVI/PGBC can be used as an effective activator for PS to remove organic pollutants in water.

Efficacy of nanoparticle encapsulation on suppressing oxidation and enhancing antifungal activity of cyclic lipopeptides produced by Bacillus subtilis.

This study examined the storage instability of cyclic lipopeptides (CLs) extracted from Bacillus subtilis culture; CLs were easily oxidized and therefore quickly lost antifungal activity during storage. Solid lipid nanoparticle (SLN) encapsulation effectively suppressed the oxidation and prolonged and enhanced the antifungal efficacy of CLs through controlled release. Thermal gravimetric analysis, X-ray diffraction, and Fourier transform infrared spectroscopy revealed that hydrophobic interactions between the fatty acid moieties of CLs and SLNs fortified the crystal structure of the CL-SLN complex, thereby improving the storage stability of the encapsulated CLs. Furthermore, the encapsulated CLs also demonstrated more potent antifungal activity than free CLs in damaging fungal cellular membranes, affecting the growth of hyphae and spores, and decreasing ochratoxin A levels. SLN encapsulation is an effective method to protect and improve the function of CLs.

Micromonospora zhangzhouensis sp. nov., a Novel Actinobacterium Isolated from Mangrove Soil, Exerts a Cytotoxic Activity in vitro.

A new bacterial strain, designated HM134T, was isolated from a sample of soil collected from a Chinese mangrove Avicennia marina forest. Assessed by a polyphasic approach, the taxonomy of strain HM134T was found to be associated with a range of phylogenetic and chemotaxonomic properties consistent with the genus Micromonospora. Phylogenetic analysis based on the 16s rRNA gene sequence indicated that strain HM134T formed a distinct lineage with the most closely related species, including M. rifamycinica AM105T, M. wenchangensis CCTCC AA 2012002T and M. mangrovi 2803GPT1-18T. The ANI values between strain HM134T and the reference strains ranged from 82.6% to 95.2%, which was below the standard criteria for classifying strains as the same species (96.5%). Strain HM134T and related species shared in silico dDDH similarities values below the recommended 70% cut-off for the delineation of species (range from 25.7-62.6%). The DNA G+C content of strain HM134T was 73.2 mol%. Analysis of phylogenetic, genomic, phenotypic and chemotaxonomic characteristics revealed that strain HM134T is considered to represent a novel species of the genus Micromonospora, for which the name M. zhangzhouensis sp. nov. is proposed. The extract of strain HM134T was demonstrated to exhibit cytotoxic activity against the human cancer cell lines HepG2, HCT-116 and A549. Active substance presented in the fermentation broth of strain HM134T was isolated by bioassay-guided analysis and purified afterwards. A new derivative of diterpenoid was identified through electrospray ionizing mass spectrometry (MS) and nuclear magnetic resonance (NMR). The compound showed different cytotoxic activities against cancer cells, with the highest cytotoxicity against HCT-116, corresponding to IC50 value of 38.4 µg/mL.

Nesterenkonia muleiensis sp. nov., a novel actinobacterium isolated from sap of Populus euphratica.

A novel, Gram-stain-positive, aerobic, non-endospore-forming, non-motile and rod-shaped bacterium designated RB2T was isolated from sap of Populus euphratica collected in Mulei county, Xinjiang province, PR China. RB2T was able to grow at 10-45 °C (optimum 35 °C), pH 6.0-12.0 (optimum 8.0) and with 0-12 % (w/v) NaCl (optimum 1 %). The genomic DNA G+C content was 63.5 % (from the genome sequence). The results of the chemotaxonomic analysis indicated that the predominant isoprenoid quinones were MK-8 and MK-9. The major fatty acids were anteiso-C15 : 0 and anteiso-C17 : 0. The major polar lipids of RB2T were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylinositol and two glycolipids. The peptidoglycan type of RB2T was A4α, l-Lys-Gly-l-Glu. The results of the phylogenetic analysis, along with the phenotypic and chemotaxonomic characteristics, indicate that strain RB2T represents a novel species of the genus Nesterenkonia, for which the name Nesterenkonia muleiensis sp. nov. is proposed. The type strain is RB2T (=MCCC 1K03528T=KCTC 49017T).

A modified LC-MS/MS method to simultaneously quantify glycerol and mannitol concentrations in human urine for doping control purposes.

Glycerol and mannitol have the potential to act as plasma volume expanders and have been prohibited as masking agents by the World Anti-Doping Agency (WADA) accordingly. In this study, an improved strategy was developed and validated for the determination of urinary glycerol and mannitol levels simultaneously using a liquid chromatography/tandem mass spectrometry technique within 7min in an initial testing procedure. For confirmation, mannitol and all possible hexitols (allitol, altritol, galactitol, iditol and sorbitol) that can occur in human urine were baseline separated. This method made use of the derivatization of glycerol and mannitol by benzoyl chloride followed by analysis via LC-ESI-MS/MS with limited sample preparation. The limit of detection (LOD) for glycerol and mannitol was lower than 50ng/mL. The limit of quantitation (LOQ) for both substances was below 150ng/mL. The assay was linear from 0.15 to 1000µg/mL for glycerol and mannitol in human urine. The coefficients of variation of all inter- and intra-assay determinations at three concentration levels (0.5, 500, 900µg/mL) were better than 13% for glycerol and under 15% for mannitol. The method also afforded satisfactory results in terms of accuracy, derivatization yield, extraction recovery, matrix effect and specificity for both substances.