Switchable ionic liquids enable efficient nanofibrillation of wood pulp

Use of switchable ionic liquid (SIL) pulp offers an efficient and greener technology to produce nanofibers via ultrafine grinding. In this study, we demonstrate that SIL pulp opens up a mechanically efficient route to the nanofibrillation of wood pulp, thus providing both a low cost and chemically benign route to the production of cellulose nanofibers. The degree of fibrillation during the process was evaluated by viscosity and optical microscopy of SIL treated, bleached SIL treated and a reference pulp. Furthermore, films were prepared from the fibrillated material for characterization and tensile testing. It was observed that substantially improved mechanical properties were attained as a result of the grinding process, thus signifying nanofibrillation. Both SIL treated and bleached SIL treated pulps were fibrillated into nanofibers with fiber diameters below 15 nm thus forming networks of hydrophilic nature with an intact crystalline structure. Notably, it was found that the SIL pulp could be fibrillated more efficiently than traditional pulp since nanofibers could be produced with more than 30% less energy when compared to the reference pulp. Additionally, bleaching reduced the energy demand by further 16%. The study demonstrated that this switchable ionic liquid treatment has considerable potential in the commercial production of nanofibers due to the increased efficiency in fibrillation.     

Characterization of sulfhydryl oxidase from <Emphasis Type="Italic">Aspergillus tubingensis</Emphasis>

Background

Despite of the presence of sulfhydryl oxidases (SOXs) in the secretomes of industrially relevant organisms and their many potential applications, only few of these enzymes have been biochemically characterized. In addition, basic functions of most of the SOX enzymes reported so far are not fully understood. In particular, the physiological role of secreted fungal SOXs is unclear.

Results

The recently identified SOX from Aspergillus tubingensis (AtSOX) was produced, purified and characterized in the present work. AtSOX had a pH optimum of 6.5, and showed a good pH stability retaining more than 80% of the initial activity in a pH range 4-8.5 within 20 h. More than 70% of the initial activity was retained after incubation at 50 °C for 20 h. AtSOX contains a non-covalently bound flavin cofactor. The enzyme oxidised a sulfhydryl group of glutathione to form a disulfide bond, as verified by nuclear magnetic resonance spectroscopy. AtSOX preferred glutathione as a substrate over cysteine and dithiothreitol. The activity of the enzyme was totally inhibited by 10 mM zinc sulphate. Peptide- and protein-bound sulfhydryl groups in bikunin, gliotoxin, holomycin, insulin B chain, and ribonuclease A, were not oxidised by the enzyme. Based on the analysis of 33 fungal genomes, SOX enzyme encoding genes were found close to nonribosomal peptide synthetases (NRPS) but not with polyketide synthases (PKS). In the phylogenetic tree, constructed from 25 SOX and thioredoxin reductase sequences from IPR000103 InterPro family, AtSOX was evolutionary closely related to other Aspergillus SOXs. Oxidoreductases involved in the maturation of nonribosomal peptides of fungal and bacterial origin, namely GliT, HlmI and DepH, were also evolutionary closely related to AtSOX whereas fungal thioreductases were more distant.

Conclusions

AtSOX (55 kDa) is a fungal secreted flavin-dependent enzyme with good stability to both pH and temperature. A Michaelis-Menten behaviour was observed with reduced glutathione as a substrate. Based on the location of SOX enzyme encoding genes close to NRPSs, SOXs could be involved in the secondary metabolism and act as an accessory enzyme in the production of nonribosomal peptides.

     

Cellulose and chitin nanomaterials for capturing silver ions (Ag+) from water via surface adsorption

The study explores the potential of cellulose nanocrystals (CNC), cellulose nanofibers (CNF) and chitin nanocrystals (ChNC) isolated from bioresidues to remove silver ions from contaminated water. Zeta sizer studies showed negatively charged surfaces for CNC and CNF isolated from cellulose sludge in the acidic and alkaline pHs, whereas ChNC isolated from crab shell residue showed either positive or negative charges depending on pH conditions. Model water containing silver ions showed a decrease in Ag⁺ ion concentration (measured by inductively coupled plasma-optical emission spectrometer; inductively coupled plasma mass spectrometry), after treatment with CNC, CNF and ChNC suspensions. The highest Ag⁺ ion removal was measured near neutral pH for CNC, being 34.4 mg/g, corresponding to 64 % removal. ChNC showed 37 % and CNF showed 27 % removal of silver ions. The WDX (wavelength dispersive X-ray analysis) and XPS (X-ray photoelectron spectroscopy) analysis confirmed the presence of silver ions on the surface of the nanocellulose and nanochitin after adsorption. Surface adsorption on the nanoparticles via electrostatic interactions is considered to be the prominent mechanism of heavy metal ion capture from aqueous medium, with CNC with negative surface charge and negatively charged functional groups being most favourable for the adsorption of positively charged Ag⁺ ions compared to other native bionanomaterials.     

Porous electrospun nanocomposite mats based on chitosan–cellulose nanocrystals for wound dressing: effect of surface characteristics of nanocrystals

Randomly oriented fiber mats of chitosan–polyethylene oxide matrix reinforced with cellulose nanocrystals (CNCs) were prepared by electrospinning technique. The cellulose nanocrystals used were isolated using hydrochloric acid (CNC_HCl) or sulphuric acid (\({\text{CNC}}_{{{\text{H}}_{ 2} {\text{SO}}_{ 4} }}\)) and the concentration of CNCs was 50 wt% in the electrospun mats. The surface characteristics of the nanocrystals were found to affect the dispersion, viscosity, conductivity and zeta-potential of the respective spinning solutions and resulted in better spinnability, homogeneity as well as crosslinking of CNC_HCl based nanocomposite fiber mats compared to \({\text{CNC}}_{{{\text{H}}_{ 2} {\text{SO}}_{ 4} }}\) ones. The microscopy studies showed that the diameter of the electrospun fibers decreased with the inclusion of both types of nanocrystals and that crosslinking decreased the porosity of the mats. The tensile strength and tensile modulus of the mats increased with the addition of nanocrystals and increased further for the CNC_HCl based mats (58 MPa, 3.1 GPa) after crosslinking. The as-spun CNC_HCl based mats had average pore diameters of 1.6 μm and porosity of 38 %. The water vapor permeability and the O₂/CO₂ transmission increased with the addition of CNC_HCl. The used nanocrystals as well as electrospun mats showed non-cytotoxic impact on adipose derived stem cells (ASCs), which was considered favorable for wound dressing.     

Effect of long fiber thermoplastic extrusion process on fiber dispersion and mechanical properties of viscose fiber/polypropylene composites

Viscose fiber reinforced polypropylene (PP/VF) composites were manufactured using long fiber thermoplastic (LFT) extrusion techniques with two different methods namely LFT‐l and LFT‐2. The compatibilizer [maleated polypropylene (MAPP)] and dispersing agent [stearic acid (SA)] were added to the PP/VF in order to improve the fiber dispersion and interfacial adhesion. The PP/VF composites manufactured using LFT‐2 showed better fiber dispersion with higher tensile and flexural properties compared to the composites manufactured using LFT‐1 method. Similarly, the impact strength and toughness of the LET‐2 composites showed an improvement of 36 and 20% than LFT‐1 whereas the average fiber length of composites was decreased from 6.9 mm to 4.4 mm because of the increase in shear energy as a result of residence time. Further, the addition of SA and MAPP to LFT‐2 process has significantly improved the fiber dispersion and mechanical performance. The fiber dispersion and fracture behavior of the LFT‐1 and LFT‐2 composites were studied using scanning electron microscopy analysis. The Fourier transformation infrared spectra were also studied to ascertain the existence of type of interfacial bonds. Copyright © 2015 John Wiley & Sons, Ltd.     

Functionalisation of Graphene Sensor Surfaces for the Specific Detection of Biomarkers

We report on a controllable and specific functionalisation route for graphene field-effect transistors (GFETs) for the recognition of small physiologically active molecules. Key element is the noncovalent functionalisation of the graphene surface with perylene bisimide (PBI) molecules directly on the growth substrate. This Functional Layer Transfer enables the homogeneous self-assembly of PBI molecules on graphene, onto which antibodies are subsequently immobilised. The sensor surface was characterised by atomic force microscopy, Raman spectroscopy and electrical measurements, showing superior performance over conventional functionalisation after transfer. Specific sensing of small molecules was realised by monitoring the electrical property changes of functionalised GFET devices upon the application of methamphetamine and cortisol. The concentration dependent electrical response of our sensors was determined down to a concentration of 300 ng ml⁻¹ for methamphetamine.     

Advanced glossmeters for industrial applications

In this paper, we present three new types of diffractive-optical-element (DOE)-based glossmeters (DOGs) that have been developed for both laboratory and online local specular gloss measurements of objects in industrial processes. The three are denoted as the handheld wireless glossmeter, μDOG two-dimensional (2D) and μDOG one-dimensional (1D), respectively. These glossmeters are designed to operate under conditions where gloss measurement with conventional glossmeters is impossible or difficult, or when fine structures of the gloss over a surface are an issue. Here, we show the applicability of the handheld glossmeter and μDOG 2D in the inspection of gloss from rough stainless steel plates finished by different machining methods. We also briefly introduce the concept of online gauge μDOG 1D for gloss assessment in industrial measurement environments.     

Enhanced chromatographic NMR with polyethyleneglycol. A novel resolving agent for diffusion ordered spectroscopy

NMR analysis of complex mixtures can be significantly simplified using polyethyleneglycol (PEG) as resolving additive in DOSY NMR technique, which allows the extraction of individual spectra of mixture components with differing polarity. Resolving power of PEG‐assisted DOSY was demonstrated with natural product mixtures. Copyright © 2010 John Wiley & Sons, Ltd.     

Crosslinked fibrous composites based on cellulose nanofibers and collagen with in situ pH induced fibrillation

Collagen and cellulose nanofiber based composites were prepared by solution casting followed by pH induced in situ partial fibrillation of collagen phase and crosslinking of collagen phase using gluteraldehyde. Microscopy studies on the materials confirmed the presence of fibrous collagen and cellulose nanofibers embedded in the collagen matrix. The cellulose nanofiber addition as well as collagen crosslinking showed significant positive impact on the nanocomposite’s mechanical behaviour. The synergistic performance of the nanocomposites indicated stabilization and reinforcement through strong physical entanglement between collagen and cellulose fibres as well as chemical interaction between collagen matrix and collagen fibrils. The mechanical performance and stability in moist conditions showed the potential of these materials as implantable scaffolds in biomedical applications. The collagen-cellulose ratio, crosslinking agent and crosslinking level of collagen may be further optimised to tailor the mechanical properties and cytocompatibility of these composites for specific applications such as artificial ligament or tendon.     

A laccase study by electrospray ionization Fourier transform ion cyclotron resonance MS: copper depletion, glycoforms and stability

The molecular properties and stability of a laccase from the white-rot fungus Trametes hirsuta (ThL) were studied to exploit the unique capability of electrospray ionization mass spectrometry (ESI-MS) to monitor conformational and molecular-based heterogeneities and metal ion binding simultaneously. Acid and organic solvents were applied as denaturing agents. In aqueous acidic solution, ThL existed in two major forms, distinguished by their mass difference; in addition to these, two other forms were detected. This molecular heterogeneity was due to the variable glycan content of ThL. Additionally, copper-depleted forms of laccase were observed in mass spectra measured from aqueous acidic solution. A small amount of organic solvent (acetonitrile, CH(3)CN) increased the loss of one Cu atom from folded states and led to unfolding. In the unfolded state, ThL was depleted of all four copper atoms, and the charge state distribution was shifted to lower mass-to-charge region. Thus, denaturation took place in two stages: first, the loss of one Cu resulting in an inactive form; second, complete denaturation with the loss of the three remaining Cu atoms. After all coppers were lost, ThL was unfolded, as was clearly seen in the increased number of charge states in the mass spectra. Different stabilities of the glycoforms were observed in the denaturation triggered in acid and organic solvents.