Search

This study investigates the impacts of bismuth and tin on the production of CH4 and volatile fatty acids in a microbial electrosynthesis cell with a continuous CO2 supply. First, the impact of several transition metal ions (Ni2+, Fe2+, Cu2+, Sn2+, Mn2+, MoO42−, and Bi3+) on hydrogenotrophic and acetoclastic methanogenic microbial activity was evaluated in a series of batch bottle tests incubated with anaerobic sludge and a pre-defined concentration of dissolved transition metals. While Cu is considered a promising catalyst for the electrocatalytic conversion of CO2 to short chain fatty acids such as acetate, its presence as a Cu2+ ion was demonstrated to significantly inhibit the microbial production of CH4 and acetate. At the same time, CH4 production increased in the presence of Bi3+ (0.1 g L−1) and remained unchanged at the same concentration of Sn2+. Since Sn is of interest due to its catalytic properties in the electrochemical CO2 conversion, Bi and Sn were added to the cathode compartment of a laboratory-scale microbial electrosynthesis cell (MESC) to achieve an initial concentration of 0.1 g L−1. While an initial increase in CH4 (and acetate for Sn2+) production was observed after the first injection of the metal ions, after the second injection, CH4 production declined. Acetate accumulation was indicative of the reduced activity of acetoclastic methanogens, likely due to the high partial pressure of H2. The modification of a carbon-felt electrode by the electrodeposition of Sn metal on its surface prior to cathode inoculation with anaerobic sludge showed a doubling of CH4 production in the MESC and a lower concentration of acetate, while the electrodeposition of Bi resulted in a decreased CH4 production. [ABSTRACT FROM AUTHOR]

The world is currently facing a global health crisis due to the rapid increase in antimicrobial-resistant bacterial infections. One of the most concerning pathogens is Acinetobacter baumannii, which is listed as a Priority 1 pathogen by the World Health Organization. This Gram-negative bacterium has many intrinsic antibiotic resistance mechanisms and the ability to quickly acquire new resistance determinants from its environment. A limited number of effective antibiotics against this pathogen complicates the treatment of A. baumannii infections. A potential treatment option that is rapidly gaining interest is "phage therapy", or the clinical application of bacteriophages to selectively kill bacteria. The myoviruses DLP1 and DLP2 (vB_AbaM-DLP_1 and vB_AbaM-DLP_2, respectively) were isolated from sewage samples using a capsule minus variant of A. baumannii strain AB5075. Host range analysis of these phages against 107 A. baumannii strains shows a limited host range, infecting 15 and 21 for phages DLP1 and DLP2, respectively. Phage DLP1 has a large burst size of 239 PFU/cell, a latency period of 20 min, and virulence index of 0.93. In contrast, DLP2 has a smaller burst size of 24 PFU/cell, a latency period of 20 min, and virulence index of 0.86. Both phages show potential for use as therapeutics to combat A. baumannii infections. [ABSTRACT FROM AUTHOR]

Cationic nanomaterials are promising candidates for the development of effective antibacterial agents by taking advantage of the nanoscale effects as well as other exceptional physicochemical properties of nanomaterials. In this study, carboxylated cellulose nanocrystals (cCNCs) derived from softwood pulp were coated with cationic poly(diallyldimethylammonium chloride) of varying molecular weights. The resulting cationic carboxylated cellulose nanocrystals coated with poly(diallyldimethylammonium chloride) (cCNCs–PDDA) nanomaterials were characterized for their structural and morphological properties using Fourier transform infrared spectroscopy, dynamic light scattering, zeta potential, elemental analysis, transmission electron microscopy, and thermogravimetric analysis. Cationic cCNCs–PDDA were investigated for their antibacterial properties against Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli 23934 and Pseudomonas aeruginosa using a bacterial lawn growth inhibition assay. cCNC–PDDA materials displayed marked antibacterial activity, particularly against Gram-positive Staphylococcus aureus. Overall, our results indicated that cCNCs–PDDA could be a potential candidate for antibacterial applications such as antibacterial surfaces or coatings. [ABSTRACT FROM AUTHOR]

To unlock nature's potential for functional biomaterials, many efforts have been devoted to isolating the nanocrystalline domains within the supramolecular structure of polysaccharides. Yet, low reactivity and yield in aqueous systems along with excessive solvent usage hinders its development. In this report, the first solvent‐free pathway to access carboxylated chitin and cellulose nanocrystals with excellent mass balance is described, relying on a new method coined high‐humidity shaker aging (HHSA). The method involves a mild grinding of the polysaccharide with ammonium persulfate followed by an aging phase under high‐humidity and on a shaker plate. Insights into the mechanism were uncovered, which highlighted the unique role of high humidity to afford a gradual uptake of water by the material up to deliquescence when the reaction is complete. This process was then validated for direct synthesis of nanocrystals from biomass sources including crab and soft wood pulp. [ABSTRACT FROM AUTHOR]

Polysaccharides have been shown to have immunomodulatory properties. Modulation of the immune system plays a crucial role in physiological processes as well as in the treatment and/or prevention of autoimmune and infectious diseases. Cellulose nanocrystals (CNCs) are derived from cellulose, the most abundant polysaccharide on the earth. CNCs are an emerging class of crystalline nanomaterials with exceptional physico-chemical properties for high-end applications and commercialization prospects. The aim of this study was to design, synthesize, and evaluate the cytotoxicity of a series of biocompatible, wood-based, cationic CNCs as potential immunomodulators. The anionic CNCs were rendered cationic by grafting with cationic polymers having pendant +NMe3 and +NH3 moieties. The success of the synthesis of the cationic CNCs was evidenced by Fourier transform infrared spectroscopy, dynamic light scattering, zeta potential, and elemental analysis. No modification in the nanocrystals rod-like shape was observed in transmission electron microscopy and atomic force microscopy analyses. Cytotoxicity studies using three different cell-based assays (MTT, Neutral Red, and LIVE/DEAD®) and three relevant mouse and human immune cells indicated very low cytotoxicity of the cationic CNCs in all tested experimental conditions. Overall, our results showed that cationic CNCs are suitable to be further investigated as immunomodulators and potential vaccine nanoadjuvants. [ABSTRACT FROM AUTHOR]

In this study, CO 2 conversion to acetate and CH 4 was achieved in a flow-through laboratory-scale microbial electrosynthesis (MES) cell composed of a 3D conductive polylactic acid (cPLA) lattice cathode with electrodeposited metal electrocatalyst coatings. The MES cell with a bare cPLA cathode showed the poorest performance with the lowest H 2 and CH 4 production rates and low Coulombic efficiency. This was ascribed to a poor electrocatalytic activity of cPLA towards H 2 production and high electrode resistivity. When the cPLA electrode was modified with metal coatings, the CH 4 , acetate and H 2 production rate increased significantly, with the following trend: cPLA < Ni < NiFe < NiFeMn. The better performance of the metal-coated cPLA in terms of CH 4 production was attributed to the lower electrical resistance, enhanced H 2 production and enhanced electron transfer between the cathode and the biofilm. At the cell potential of 2.8 V, the best-performing NiFeMn cPLA cathode showed stable production of CH 4 (50 ± 6 mL d−1), acetate (185 ± 27 mg d−1), and H 2 (545 ± 175 mL d−1) at close to 100% Coulombic efficiency. [Display omitted] • Conductive polylactate (cPLA) lattice cathode developed for microbial electrosynthesis. • CH 4 , acetate, and H 2 continuously produced in a microbial electrosynthesis (MES) cell. • Electrodeposition of Ni, Fe, and Mn increased cPLA performance by up to 80%. • NiFeMn cPLA showed best performance with nearly 100% Coulombic efficiency. [ABSTRACT FROM AUTHOR]

In this report, chitin and chitosan nanocrystals were used as biomass-based supports for Pd nanoparticles (NPs) used as a heterogeneous catalyst for the Heck coupling reaction. By using a one-pot fabrication method, a Pd salt precursor was directly reduced and deposited onto these nanocrystal catalysts. Characterization of these nanocomposites showed disperse Pd NPs on the surfaces of the chitinous nanocrystals. Heck coupling model reactions revealed full product yield in relatively benign conditions, outcompeting the use of other catalysts supported on biomass-based nanomaterials, including cellulose nanocrystals. These initial results show the potential for using chitinous nanomaterials as effective catalyst supports in cross-coupling reactions., (Copyright © 2020, Jin et al.; licensee Beilstein-Institut.)

In this study, we demonstrate for the first time the fabrication of carboxylated chitosan nanocrystals (ChsNC) with high degree of deacetylation (DDA) at >80% and narrow size distribution. We also studied its application as a sustainable support material for metal-based catalysts. Carboxylated chitin nanocrystals (ChNCs) were initially prepared through partial cleavage of glycosidic bonds in chitin by ammonium persulfate, with concurrent oxidation of chitin C6 primary alcohols to produce carboxylate groups on the surface of the ChNCs. ChsNCs were subsequently prepared using an alkaline deacetylation procedure in the presence of NaBH 4 to preserve the nanorod structure of the biomaterial. The resulting nanocrystals feature both carboxyl and amino functional groups. Transmission electron microscopy (TEM), X-ray diffraction (XRD), and Fourier-transform infrared (FTIR) spectroscopy were used to determine the morphology and composition of these carboxylated ChNCs and ChsNCs. Subsequently, we tested the ability of the as-made ChsNCs as a biomass-based catalyst support for Au nanoparticles (NPs) using the 4-nitrophenol reduction and the aldehyde-amine-alkyne (A 3 ) coupling reactions to demonstrate its capabilities in regard to the ones of cellulose nanocrystals (CNCs). In particular, Au NPs over ChsNCs featured the highest turnover frequency (TOF) value for the 4-nitrophenol reduction reported for all Au-based catalysts supported on carbon-based systems. Spectroscopic and imaging techniques confirmed the importance of precisely controlling the redox state of Au as it is being deposited to afford a highly disperse active site on the bionano-support.