Expression, Characterization and Structure Analysis of a New GH26 Endo-β-1, 4-Mannanase (Man26E) from Enterobacter aerogenes B19

β-mannanase is one of the key enzymes to hydrolyze hemicellulose. At present, most β-mannanases are not widely applied because of their low enzyme activity and unsuitable enzymatic properties. In this work, a new β-mannanase from Enterobacter aerogenes was studied, which laid the foundation for its further application. Additionally, we will further perform directed evolution of the enzyme to increase its activity, improve its temperature and pH properties to allow it more applications in industry. A new β-mannanase (Man26E) from Enterobacter aerogenes was successfully expressed in Escherichia coli. Man26E showed about 40 kDa on SDS-PAGE gel. The SWISS-MODEL program was used to model the tertiary structure of Man26E, which presented a core (α/β)8-barrel catalytic module. Based on the binding pattern of CjMan26 C, Man26E docking Gal1Man4 was investigated. The catalytic region consisted of a surface containing four solvent-exposed aromatic rings, many hydrophilic and charged residues. Man26E displayed the highest activity at pH 6.0 and 55 °C, and high acid and alkali stability in a wide pH range (pH 4–10) and thermostability from 40 to 50 °C. The enzyme showed the highest activity on locust bean gum, and the Km and Vmax were 7.16 mg mL−1 and 508 U mg−1, respectively. This is the second β-mannanase reported from Enterobacter aerogenes B19. The β-mannanase displayed high enzyme activity, a relatively high catalytic temperature and a broad range of catalytic pH values. The enzyme catalyzed both polysaccharides and manno-oligosaccharides.

The application of organosilicon modified polyurethane in reinforcing traditional paper

Paper relics are important historical and cultural heritages. However, the paper relics are at risk of ageing, damage and disappearance. In order to delay the aging of paper, improve the strength of paper, solve the problem of poor permeability and stability of traditional resins to paper, the polyurethane was synthesized by polydimethylsiloxane (HTPDMS) and low molecular weight hexamethylene diisocyanate (HDI) trimer, and the chemical and physical properties of paper samples were tested. Results showed the paper coated by HTPDM-modified polyurethane liquid had good mechanical property, the tensile strength was increased from 1105 to 3299 N/m, the folding endurance was increased from 20 to 1024; and had good gloss and brightness; after thermal aging, coated paper can effectively maintain tensile strength, delay folding resistance and tearing strength loss; after acid stability test, the loss ratio of tensile strength was decreased from 34.2 % to 15.7 %, folding endurance was decreased from 57.1 % to 9.7 %; after alkali stability test, the loss ratio of tensile strength was decreased from 29.3 % to 6.6 %, folding endurance was decreased from 82.9 % to 22.0 %. Therefore, the prepared polyurethane material has great application prospects in the protection of paper.

A facile approach to prepare crosslinked polysulfone-based anion exchange membranes with enhanced alkali resistance and dimensional stability

Novel anion exchange membranes with enhanced ion exchange capacity, dimensional stability and alkali stability were prepared by a facile synthesis method.

A high conductivity ultrathin anion-exchange membrane with 500+ h alkali stability for use in alkaline membrane fuel cells that can achieve 2 W cm−2 at 80 °C

This article describes the development of a sub-30 μm thick LDPE-based radiation-grafted anion-exchange membrane (RG-AEM) with high performance characteristics when fully hydrated.