Complementary spectroscopy studies and potential activities of levan-type fructan produced by Bacillus paralicheniformis ND2.

This study aimed at the production of marine bacterial exopolysaccharides (EPS) as biodegradable and nontoxic biopolymers, competing the synthetic derivatives, with detailed structural and conformational analyses using spectroscopy techniques. Twelve marine bacterial bacilli were isolated from the seawater of Mediterranean Sea, Egypt, then screened for EPS production. The most potent isolate was identified genetically as Bacillus paralicheniformis ND2 by16S rRNA gene sequence of ~99 % similarity. Plackett-Burman (PB) design identified the optimization conditions of EPS production, which yielded the maximum EPS (14.57 g L-1) with 1.26-fold increase when compared to the basal conditions. Two purified EPSs namely NRF1 and NRF2 with average molecular weights (Mw¯) of 15.98 and 9.70 kDa, respectively, were obtained and subjected for subsequent analyses. FTIR and UV-Vis reflected their purity and high carbohydrate contents while EDX emphasized their neutral type. NMR identified the EPSs as levan-type fructan composed of ß-(2-6)-glycosidic linkage as a main backbone, and HPLC explained that the EPSs composed of fructose. Circular dichroism (CD) suggested that NRF1 and NRF2 had identical structuration with a little variation from the EPS-NR. The EPS-NR showed antibacterial activity with the maximum inhibition against S. aureus ATCC 25923. Furthermore, all the EPSs revealed a proinflammatory action through dose-dependent increment of expression of proinflammatory cytokine mRNAs, IL-6, IL-1ß and TNFα.

Statistical optimization of experimental parameters for extracellular synthesis of zinc oxide nanoparticles by a novel haloalaliphilic Alkalibacillus sp.W7.

Green synthesis of zinc oxide nanoparticles (ZnO NPs) through simple, rapid, eco-friendly and an economical method with a new haloalkaliphilic bacterial strain (Alkalibacillus sp. W7) was investigated. Response surface methodology (RSM) based on Box-Behnken design (BP) was used to optimize the process parameters (ZnSO4.7H2O concentration, temperature, and pH) affecting the size of Alkalibacillus-ZnO NPs (Alk-ZnO NPs). The synthesized nanoparticles were characterized using UV-visible spectrum, X-ray diffraction (XRD), Scanning electron microscope-energy dispersive X-ray spectroscopy (SEM-EDX), Transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR) and Zeta potential. The UV-Vis spectrum of ZnO NPs revealed a characteristic surface plasmon resonance (SPR) peak at 310 nm. XRD pattern confirmed the hexagonal wurtzite structure of highly pure with a crystallite size 19.5 nm. TEM proved the quasi-spherical shape nanoparticles of size ranging from 1 to 30 nm. SEM-EDX showed spherical shaped and displayed a maximum elemental distribution of zinc and oxygen. FTIR provided an evidence that the biofunctional groups of metabolites in Alkalibacillus sp.W7 supernatant acted as viable reducing, capping and stabilizing agents.

Optimization of methylene blue degradation by Aspergillus terreus YESM 3 using response surface methodology.

Synthetic dyes released from many industries cause pollution problems in aquatic environments affecting public health. The present study aimed to explore the potentiality of Aspergillus terreus YESM 3 (accession number LM653117) for colour removal of three different dyes: methylene blue (MB), malachite green (MG) and safranin (S). Results showed that the tolerance index of the studied fungus against tested dyes decreased in the order: methylene blue, safranin and malachite green. Removal of methylene blue colour was improved by using Box-Behnken design. Optimum condition for methylene blue biodegradation in Czapek Dox broth was achieved at pH 6, of 31.41 mg/L dye concentration and an inoculum of 5.7778 × 104 (conidia/mL) with biodegradation of 89.41%. Thus, a novel and eco-friendly system for the biodegradation of dyes using Box-Behnken design has been efficiently developed. Accordingly, A. terreus YESM 3 can be professionally used for bioremediation of methylene blue dye in wastewater and removal of environmental pollution.

Hexavalent chromium reduction by chromate-resistant haloalkaliphilic Halomonas sp. M-Cr newly isolated from tannery effluent.

The current study aimed to isolate and characterize a chromate-resistant bacterium from tannery effluent, able to reduce Cr(VI) aerobically at high pH and salinity. Environmental contamination by hexavalent chromium, Cr(VI), presents a serious public health problem. Enrichment led to the isolation of 12 bacteria displaying different degrees of chromate reduction. Phenotypic characterization and phylogenetic analysis based on 16S rDNA sequence comparison indicated that the most potent strain belonged to the genus Halomonas. The new strain designated as Halomonas sp. M-Cr was able to reduce 82% of 50 mg L-1 Cr(VI) in 48 h, concomitant with discolouring of yellow colour of the medium and formation of white insoluble precipitate of Cr(III). It exhibited growth up to 3500 mg L-1 Cr(VI), 20% NaCl and showed strong Cr(VI) reduction under alkaline condition, pH 10. Scanning electron microscopy revealed precipitation of chromium hydroxide on bacterial cell surfaces, which showed characteristic peak of chromium in energy-dispersive X-ray analysis. Plackett-Burman design was used to evaluate the influence of related parameters for enhancing Cr(VI) reduction. Glucose, yeast extract and KH2PO 4 were confirmed as significant variables in the medium. Data suggest Halomonas sp. M-Cr as a promising candidate for bioremediation of Cr(VI) contaminated effluents particularly in saline and alkaline environments. Up to our knowledge, this is the first report on isolation of haloalkaliphilic Halomonas sp. from tannery effluent.

Isolation and characterization of a phenol-degrading strain of Alcaligenes sp. AM4.

Six isolates with phenol degrading ability were obtained from marine sediments by enrichment procedures and an isolate, AM4, was identified as Alcaligenes sp. by 16S rDNA sequencing. The Plackett-Burman design was applied to estimate the significance of culture medium components and conditions for phenol degradation by Alcaligenes sp. AM4. The resulting medium formula which was predicted to be near optimal was: phenol conc. (240 µg/ml), culture volume (37.5 ml), inoculum's size (0.15 ml), NH4SO4 (0.5 g/l), K2HPO4 (0.75 g/l), KH2PO4 (0.75 g/l), MgSO4 (0.3 g/l) and NaCl (0.25 g/l). Scanning electron microscopy was applied to cells exposed to phenol, and a larger cell size was detected, resulting in a reduced cell surface. This relative reduction of the cell surface represents a cellular mechanism to reduce the toxic effect of this environmental stress factor.