A multifunctional Ag NPs/guar gum hydrogel as versatile platform for catalysts, antibacterial agents, and construction of oil-water separation interfaces.

The frequently encountered wastewater contaminations, including soluble aromatic compound and dye pollutants, pathogenic bacteria, and insoluble oils, have resulted in significant environmental and human health issues. It poses a challenge to utilize identical materials for the treatment of complex wastewater. Herein, in this research, multifunctional Ag NPs/guar gum hybrid hydrogels were fabricated using a facile in situ reduction and self-crosslinking method for efficient remediation of complex wastewater. The Ag NPs/guar gum hybrid hydrogel showed remarkable remodeling, adhesive, and self-healing characteristics, which was favorable for its versatile applications. The combination of Ag NPs with the guar gum skeleton endowed the hybrid hydrogel with exceptional catalytic activity for reducing aromatic compounds and dye pollutants, as well as remarkable antibacterial efficacy against pathogenic bacteria. In addition, the Ag NPs/guar gum hybrid hydrogel could be employed to coat a variety of substrates, including cotton fabrics and stainless steel meshes. The hydrogel coated cotton fabrics and meshes presented superhydrophilicity/underwater superoleophobicity, excellent antifouling capacity, and outstanding recyclability, which could be successfully applied for efficient separation of oil-water mixtures. The findings of this work provide a feasible and cost-effective approach for the remediation of intricate wastewater.

Mussel-Inspired Ag NPs Immobilized on Melamine Sponge for Reduction of 4-Nitrophenol, Antibacterial Applications and Its Superhydrophobic Derivative for Oil-Water Separation.

A functional material integrated with a variety of functions is highly desired in wastewater treatment. In this research, a mussel-inspired method of immobilizing silver nanoparticles on the skeleton of a melamine sponge is proposed and applied for water remediation. Ag NPs were reduced in situ and grown on a polydopamine-modified melamine sponge. The catalytic reduction of 4-nitrophenol (4-NP) in the presence of the obtained MS-PDA-Ag was evaluated, and the results demonstrated that the MS-PDA-Ag presented high catalytic reduction activity. In addition, the monolithic MS-PDA-Ag presents excellent reusability with no remarkable decrease in catalytic efficiency after multiple reuses. Owing to the immobilized Ag NPs, the MS-PDA-Ag can also effectively inhibit the growth of bacteria against both gram-positive and gram-negative species, making it possible for bacteria elimination in polluted water. To further explore the possibility of utilizing the MS-PDA-Ag for versatile applications, a superhydrophobic derivative (S-MS-PDA-Ag) was prepared by coating a low-surface-energy substance (octadecanethiol) on the surface of MS-PDA-Ag. The obtained S-MS-PDA-Ag presents the capacities of oil/organics adsorption and water repellence, which can separate the insoluble oil/organics from water. The melamine sponge immobilized with Ag NPs demonstrates prominent catalytic reduction of 4-NP, antibacterial activity and the superhydrophobic derivative presents the capacity of insoluble oil/organics separation from oil-water mixtures, exhibiting high potential in the remediation of polluted water.

Purification and characterisation of polyphenol oxidase from leaves of Cleome gynandra L.

A polyphenol oxidase was purified and characterised from leaves of the common spiderflower. Purification sequentially with ammonium sulphate, dialysis, DEAE-Sepharose ion-exchange chromatography and Sephadex G-75 gel filtration chromatography resulted in 37.8-fold enrichment in the specific activity and 44.3% recovery of the total activity. Purified PPO is a monomeric protein of 52.6kDa revealed by Coomassie and active staining and Western blot. It was optimally active at pH 8.0 and 60°C, and stable from pH 3.0 to 9.0 and below 60°C. It displayed enzymatic activity towards monophenols, diphenols and triphenols, especially towards diphenols, and substrate specificity towards methylated and methoxylated substrates. Its activity was slightly increased by 0.1% SDS, heavily inhibited by Hg(2+) and Pb(2+), and completely inhibited by 1.0mM of ascorbic acid, l-cysteine, ß-mercaptoethanol, sodium diethyldithiocarbamate and thiourea, and by 10mM of dithioerythritol, sodium metabisulphite and sodium sulphite.