Hydrogen production properties of Rhodobacter capsulatus with genetically modified redox balancing pathways

Rhodobacter capsulatus produces molecular hydrogen under the photoheterotrophic growth condition with reduced carbon sources (organic acids). Under this condition, ubiquinol pool is over reduced and excess reducing equivalents are primarily consumed via the reduction of CO₂ through the Calvin–Benson–Bassham (CBB) pathway, the dimethylsulfoxide reductase (DMSOR) system or by the reduction of protons into hydrogen gas with the use of nitrogenase to maintain a balanced intracellular oxidation-reduction potential (redox balance). In order to investigate the effect of redox balancing pathways on nitrogenase-dependent hydrogen production, CO₂ fixation was blocked by inactivating the phosphoribulokinase (PRK) of CBB pathway in wild type (MT1131), uptake-hydrogenase deficient strain (YO3), and cyt cbb₃ oxidase and uptake-hydrogenase deficient double mutant (YO4) strains. The hydrogen production properties of newly generated strains deficient in the CBB pathway were analyzed and compared with wild type strains. The obtained data indicated that, the total hydrogen production was increased slightly in CBB deficient mutant of YO3 and YO4 (4.7% and 12.5% respectively). Moreover, the maximum hydrogen production rate was increased by 13.3% and 12.7% for CBB deficient mutant of MT1131 and YO3 respectively. It was also observed that under the photoheterotrophic growth condition with ammonium as a nitrogen source, PRK deficient strains gave photoheterotrophically competent ammonium insensitive revertants.     

Batteries and a pinch of salt: A simple toolkit for the production of poly(methylsilyne)

A simple synthesis of poly(methylsilyne) has been developed. The straightforward polymerization reaction can be accomplished using simply a series of batteries and a very simple electrolyte. Poly(methylsilyne) has previously been shown to be a high‐purity, high‐yield precursor to stoichometric silicon carbide. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Chitosan formulations for steroid delivery: effect of formulation variables on in vitro characteristics

Chitosan film formulations for steroid delivery after craniomaxillofacial surgery were formulated by using three different types of chitosan with respect to their molecular weight as low, medium and high. Film formulations were prepared by casting/solvent evaporation technique. In vitro characterization, film thickness, equilibrium swelling degree, in vitro release profiles and surface morphologies were investigated. For two different types of crosslinkings, the release of dexamethasone sodium phosphate (DSP) can be extended as the molecular weight increases. As a result, chitosan film formulations should be beneficial for steroid delivery for a certain time after craniomaxillofacial surgery.     

Use of functionalized boehmite nanoparticles to improve the hardness and tribological properties of polyurethane films

Plate-like boehmite nanoparticles (BH) produced from aluminum hydroxide by hydrothermal process were functionalized in one step with two different diisocyanates. The amount of free isocyanates that were available for polymerization reaction was determined to be higher in functionalization with the aromatic diisocyanate (diphenylmethane-4,4′-di-isocyanate – MDI). In composite film production MDI functionalized BH (MDI-BH) was used. Polyurethane based nanocomposite films were produced through polymerization of non-functionalized and MDI-BH with two different polyester-polyols that were synthesized by the esterification of 1,4 butanediol with either adipic acid or phthalic anhydride. It was impossible to form films suitable for hardness and tribological tests with non-functionalized BH. Up to 1 wt% MDI-BH additions were effective in increasing the hardness and scratch resistance of films. The increases in abrasion resistance were more significant and followed the increasing trend for MDI-BH additions even up to 5 wt%. The highest increase, which was 400% with respect to the unmodified resin was observed with adipic acid based polyols and this result was obtained at MDI-BH content of 3 wt%.     

Evaluation of hydrogen production by Rhodobacter sphaeroides O.U.001 and its hupSL deficient mutant using acetate and malate as carbon sources

Rhodobacter sphaeroides O.U.001 is one of the candidates for photobiological hydrogen production among purple non-sulfur bacteria. Hydrogen is produced by Mo-nitrogenase from organic acids such as malate or lactate. A hupSL in frame deletion mutant strain was constructed without using any antibiotic resistance gene. The hydrogen production potential of the R. sphaeroides O.U.001 and its newly constructed hupSL deleted mutant strain in acetate media was evaluated and compared with malate containing media. The hupSL⁻R. sphaeroides produced 2.42 l H₂/l culture and 0.25 l H₂/l culture in 15 mM malate and 30 mM acetate containing media, respectively, as compared to the wild type cells which evolved 1.97 l H₂/l culture and 0.21 l H₂/l culture in malate and acetate containing media, correspondingly. According to the results, hupSL⁻R. sphaeroides is a better hydrogen producer but acetate alone does not seem to be an efficient carbon source for photoheterotrophic H₂ production by R. sphaeroides.     

Distribution of interface traps in Au/2% GC-doped Ca3Co4Ga0.001Ox/n-Si structures

This study presents voltage-dependent profile of interface traps in Au/n-Si structure with 2% graphene–cobalt-doped Ca₃Co₄Ga_0.001O_x interfacial layer. Admittance measurements revealed capacitance-voltage (C-V) plots with typical regions of a metal–insulator–semiconductor structure through inversion, depletion, and accumulation regions. Frequency dispersion is observed in C-V plots and such behavior was explained with excess capacitance, which is associated with the density of interface traps (D_it) in the structure because larger D_it is observed when the measurements are held at low frequencies due to the fact that traps can follow the signal depending on their lifetime. D_it was also obtained using conductance method, which also provided lifetime of the traps. The difference between the values of D_it was attributed to the difference in extraction methods. Obtained results showed that Au/2% graphene–cobalt-doped Ca₃Co₄Ga_0.001O_x/n-Si structure yields promising electrical characteristics when the structure is operated at high frequencies. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48399.     

Scanning electron microscopic studies of porous carbon electrodes used in alkaline fuel cells

Multilayer, polytetrafluoroethylene (PTFE)-bonded gas diffusion-type electrodes were prepared by the rolling method. Changing the electrode structure and manufacturing method improved alkaline fuel cell performance. Activated carbon or carbon black was used as the support material, with platinum as a catalyst and nickel screen as the backing material. Double-layer electrodes possessed both active and diffusion layers on the backing layer. However, the single-layer electrodes had only the active layer on the backing layer. The electrodes were prepared by using different PTFE contents and platinum loadings. In this study the surface photographs of the electrodes were taken with a scanning electron microscope. Elemental analyses of the surface elements were performed by energy dispersive X-ray spectroscopy (EDXS). Electrodes having activated carbon on their surfaces were observed to possess a nonuniform and porous structure. These electrodes showed better performance than electrodes having carbon black, which presented a uniform and nonporous structure.     

Composition of Carotenoids in <Emphasis Type="Italic">Scenedesmus protuberans</Emphasis>: Application of Chromatographic and Spectroscopic Methods

This study aimed to identify and determine the carotenoids from green microalga, Scenedesmus protuberans using analytical techniques. Identification of carotenoids was realized by comparing their absorption and mass spectral data with those of reference standards available and reported values. Chromatographic data were then combined with the spectroscopic information. The separation of carotenoids was achieved by C₃₀ column and high-performance liquid chromatography-diode array detection was used for their determination. In the present work, the carotenoid content of S. protuberans was found to be 1.45 mg/g of violaxanthin, 2.47 mg/g of all-trans-lutein, 0.15 mg/g of all-trans-α-carotene, 0.55 mg/g of all-trans-β-carotene, and 0.20 mg/g of 9 or 9′-cis-β-carotene. Due to lack of their standards, the amount of all-trans-loroxanthin and cis-isomers of other carotenoids could not be quantified. In order to validate the method, Certified Reference Material (BCR 485-Mixed vegetables) was used. In conclusion, this study can serve as a reference for the analysis of carotenoids in other microalgae.     

Effect of Pd loading in Pd-Pt bimetallic catalysts doped into hollow core mesoporous shell carbon on performance of proton exchange membrane fuel cells

A significantly active Pd-Pt/carbon electrocatalyst for polymer electrolyte membrane fuel cells was synthesized by microwave irradiation using a hollow core mesoporous shell (HCMS) carbon as catalyst support that was prepared by template replication of core/shell spherical silica particles and two different carbon precursors. Pt/Pd percent weight ratios on carbon support were varied as 20/0, 15/5, 10/10, 5/15 to 0/20. As the average pore diameter of the carbon support was increased from 3.02 nm to 3.90 nm by changing the type of the carbon precursor, fuel cell performances of the HCMS carbon based Pd-Pt bimetallic catalysts were improved significantly.     

Antifungal activity of biopolymers containing natamycin and rosemary extract against Aspergillus niger and Penicillium roquefortii

Antimicrobial agent‐releasing films have been proposed as an effective way of inhibiting chiefly surface spoilage of food products. Antifungal activities of natamycin (NA), rosemary extract (RE) and NA + RE were tested against Aspergillus niger and Penicillium roquefortii with agar disc diffusion assay. NA, RE and NA + RE were also included into biopolymers made from gluten and methyl cellulose. Minimum inhibitory concentrations (MIC) of NA in both films were 2 and 1 mg NA per 10 g film solution against A. niger and P. roquefortii, respectively. RE did not show any inhibitory antifungal activity alone. Although NA incorporated into both films at a concentration of 1.5 mg NA per 10 g film solution was not effective against A. niger, combination of NA at the same concentration with RE in the films inhibited the growth of this mould. NA in solution or in biopolymers is very effective in inhibiting the growth of selected organisms, and RE acted synergistically with NA to prevent the growth of A. niger when incorporated into both films.