Xylanase treatment of eucalypt kraft pulps: effect of carryover.

The influence of pulp carryover on the efficiency of the xylanase (X) treatment of industrial unbleached and oxygen-delignified eucalypt kraft pulps (A1 and A2 pulps, with kappa number (KN) values of 16 and 10, respectively), collected at the same pulp mill, was studied regarding the consumption of bleaching chemicals and pulp bleachability. Another non-oxygen-delignified eucalyptus kraft pulp of KN 13 was received after the extended cooking from a different pulp mill (pulp B). The assays were performed with both lab-washed (carryover-free) and unwashed (carryover-rich) pulps. Both lab-washed and unwashed pulps with carryover were subjected to X treatment, the former being demonstrating considerably higher ClO2 savings than the pulps containing carryover. The savings of bleaching reagents were higher when the X stage was applied to the A1 pulp than to the A2 pulp. This advantage of A1 pulp, however, was not confirmed when using unwashed pulps. In contrast, the gains obtained from the X treatment of unwashed pulp A2 were practically as high as those observed for the lab-washed A2 pulp. Furthermore, a similar effect in X stage was recorded for unwashed pulps having close KN: oxygen-delignified A2 pulp and non-oxygen-delignified B pulp. The results suggest that pulp carryover and initial pH were the key factors relating to the effectiveness of X treatment. The application of X treatment to the A2 unwashed pulp (after the oxygen stage) not only saved 20% of the ClO2 and 10% of the sodium hydroxide, but also improved the brightness stability of the bleached pulp without affecting its papermaking properties. KEY POINTS: • Xylanase treatment boosts kraft pulp bleaching • Pulp carryover hinders the xylanase treatment • Nearly 20% of ClO2 and 10% NaOH savings can be reached using xylanase.

Advances and Challenges in Plant Sterol Research: Fundamentals, Analysis, Applications and Production.

Plant sterols (PS) are cholesterol-like terpenoids widely spread in the kingdom Plantae. Being the target of extensive research for more than a century, PS have topped with evidence of having beneficial effects in healthy subjects and applications in food, cosmetic and pharmaceutical industries. However, many gaps in several fields of PS's research still hinder their widespread practical applications. In fact, many of the mechanisms associated with PS supplementation and their health benefits are still not fully elucidated. Furthermore, compared to cholesterol data, many complex PS chemical structures still need to be fully characterized, especially in oxidized PS. On the other hand, PS molecules have also been the focus of structural modifications for applications in diverse areas, including not only the above-mentioned but also in e.g., drug delivery systems or alternative matrixes for functional foods and fats. All the identified drawbacks are also superimposed by the need of new PS sources and technologies for their isolation and purification, taking into account increased environmental and sustainability concerns. Accordingly, current and future trends in PS research warrant discussion.

Recent Advances in the Production and Applications of Ellagic Acid and Its Derivatives. A Review.

Ellagitannins (ETs), characterized by their diversity and chemical complexity, belong to the class of hydrolysable tannins that, via hydrolysis under acidic or alkaline conditions, can yield ellagic acid (EA). They are mostly found as a part of extractives in angiosperms. As known antioxidants and chelators, EA and EA derivatives are drawing an increasing interest towards extensive technical and biomedical applications. The latter ones include possible antibacterial, antifungal, antiviral, anti-inflammatory, hepato- and cardioprotective, chemopreventive, neuroprotective, anti-diabetic, gastroprotective, antihyperlipidemic, and antidepressant-like activities, among others. EA's synthesis and production challenges prompt further research on new methods and alternative sources. Conventional and prospective methods and raw materials for the production of EA and its derivatives are reviewed. Among the potential sources of EA, the residues and industrial streams of the pulp industry have been highlighted and considered as an alluring alternative in terms of commercial exploitation.

Lignin Modification Supported by DFT-Based Theoretical Study as a Way to Produce Competitive Natural Antioxidants.

The valorization of lignins as renewable aromatic feedstock is of utmost importance in terms of the use of sustainable resources. This study provides a deductive approach towards market-oriented lignin-derived antioxidants by ascertaining the direct effect of different structural features of lignin on the reactivity of its phenolic OH groups in the radical scavenging reactions. The antioxidant activity of a series of compounds, modeling lignin structural units, was experimentally characterized and rationalized, using thermodynamic descriptors. The calculated O-H bond dissociation enthalpies (BDE) of characteristic lignin subunits were used to predict the modification pathways of technical lignins. The last ones were isolated by soda delignification from different biomass sources and their oligomeric fractions were studied as a raw material for modification and production of optimized antioxidants. These were characterized in terms of chemical structure, molecular weight distribution, content of the functional groups, and the antioxidant activity. The developed approach for the targeted modification of lignins allowed the products competitive with two commercial synthetic phenolic antioxidants in both free radical scavenging and stabilization of thermooxidative destruction of polyurethane films.

High pressure-promoted xylanase treatment to enhance papermaking properties of recycled pulp.

Industrially produced bleached recycled pulp (R) comprising essentially hardwood fibres was subjected to enzymatic treatment with endo-xylanase from Thermomyces lanuginosus with or without ultra-high hydrostatic pressure (UHP) pre-treatment at 300-600 MPa for 10 min. The kinetics and the extent of enzymatic hydrolysis after UHP pre-treatment under different conditions have been evaluated by released reducing sugars and the analysis of neutral sugars in pulps, respectively. The changes in surface chemical composition of pulps were assessed by UV-vis diffuse reflectance spectroscopy. UHP-pre-treated R under optimal conditions (400 MPa), with or without posterior enzymatic treatment, was used for the production of handsheets and evaluation of its mechanical properties. It was suggested that enzymatic modification improves significantly the papermaking properties of recycled pulp. These improvements were related with selective removal of xylan bound to impurities and to aggregated cellulose fibrils on the fibre surface, thus favouring the ensuing swelling and inter-fibre bonding in paper. UHP pre-treatment and posterior enzymatic treatment revealed a synergetic effect on the mechanical properties of recycled pulp. This fact was assigned to enhanced accessibility of fibres towards xylanase and by forced hydration and favourable rearrangement of cellulosic fibrils in fibres after UHP pre-treatment. The increase of basic strength properties after UHP-promoted xylanase treatment was up to 30 % being the most pronounced for the tensile strength and the burst resistance.

Novel bioemulsifier produced by a Paenibacillus strain isolated from crude oil.

BACKGROUND: Surface active compounds produced by microorganisms are attracting a pronounced interest due to their potential advantages over their synthetic counterparts, and to the fact that they could replace some of the synthetics in many environmental and industrial applications. RESULTS: Bioemulsifier production by a Paenibacillus sp. strain isolated from crude oil was studied. The bioemulsifier was produced using sucrose with and without adding hydrocarbons (paraffin or crude oil) under aerobic and anaerobic conditions at 40°C. It formed stable emulsions with several hydrocarbons and its emulsifying ability was not affected by exposure to high salinities (up to 300 g/l), high temperatures (100°C-121°C) or a wide range of pH values (2-13). In addition, it presented low toxicity and high biodegradability when compared with chemical surfactants. A preliminary chemical characterization by Fourier Transform Infrared Spectroscopy (FT-IR), proton and carbon nuclear magnetic resonance (1H NMR and 13C CP-MAS NMR) and size exclusion chromatography indicated that the bioemulsifier is a low molecular weight oligosaccharide-lipid complex. CONCLUSION: The production of a low molecular weight bioemulsifier by a novel Paenibacillus strain isolated from crude oil was reported. To the best of our knowledge, bioemulsifier production by Paenibacillus strains has not been previously reported. The features of this novel bioemulsifier make it an interesting biotechnological product for many environmental and industrial applications. Graphical Abstract Novel bioemulsifier from Paenibacillus sp.

Photodegradation of 2-mercaptobenzothiazole and 1,2,3-benzotriazole corrosion inhibitors in aqueous solutions and organic solvents.

The photochemical degradation of 2-mercaptobenzothiazole (MBT) and 1,2,3-benzotriazole (BTA) inhibitors was studied in the present work in aqueous and in organic solutions. The extent of photodegradation was assessed by UV-Vis spectroscopy and the main reaction products were identified by tandem electrospray ionization mass spectrometry (ESI-MS/MS). The analysis of degradation products upon UV irradiation revealed the predominant formation of dimeric compounds from MBT and oligomeric structures from BTA, which were further converted into aniline. The increase of the quantum yield of MBT and BTA photodegradation reactions under aerobic conditions both in aqueous and organic solvents was explained by an increase of the spin-orbit conversion of the singlet radical pairs into the triplet radical pairs in the presence of oxygen. These triplet pairs further dissociate into free radicals, or convert to the parent compounds. At the early stage of UV irradiation, free radical coupling leads essentially to dimer formation in the case of MBT and to the formation of oligomers in the case of BTA irradiation.

The study of galactomannans with different molecular weights and their ability to form microparticles suitable for pulmonary delivery.

The influence of locust bean gum (LBG) galactomannans (GMs) molecular weight (Mw) to assemble microparticulate systems was evaluated, and carriers for deep lung delivery were developed. A commercial batch of LBG with a mannose/galactose (M/G) ratio of 2.4 (batch 1) was used to study the influence of different microwave partial acid hydrolysis conditions on carbohydrate composition, glycosidic linkages, and aqueous solutions viscosity. The microwave treatment did not affect the composition, presenting 4-Man (36-42 %), 4,6-Man (27-35 %), and T-Gal (24-25 %) as the main glycosidic linkages. Depolymerization led to a viscosity reduction (≤0.005 Pa·s) with no major impact on polysaccharide debranching. The structural composition of the LBG galactomannans were further elucidated with sequence-specific proteins using carbohydrate microarray technologies. A second batch of LBG (M/G 3.3) was used to study the impact of GMs with different Mw on microparticle assembling, characteristics, and insulin release kinetics. The low-Mw GMs microparticles led to a faster release (20 min) than the higher-Mw (40 min) ones, impacting the release kinetics. All microparticles exhibited a safety profile to cells of the respiratory tract. However, only the higher-Mw GMs allowed the assembly of microparticles with sizes suitable for this type of administration.

Potentiometric chemical sensors from lignin-poly(propylene oxide) copolymers doped by carbon nanotubes.

Hardwood and softwood lignins obtained from industrial sulphite and kraft and laboratory oxygen-organosolv pulping processes were employed in co-polymerization with tolylene 2,4-diisocyanate terminated poly(propylene glycol). The obtained lignin-based polyurethanes were doped with 0.72 w/w% of multiwall carbon nanotubes (MWCNTs) with the aim of increasing their electrical conductivity to the levels suitable for sensor applications. Effects of the polymer doping with MWCNTs were assessed using electrical impedance (EIS) and UV-Resonance Raman (UV-RR) spectroscopy. Potentiometric sensors were prepared by drop casting of liquid polymer on the surface of carbon glass or platinum electrodes. Lignin-based sensors displayed a very low or no sensitivity to all alkali, alkali-earth and transition metal cations ions except Cr(VI) at pH 2. Response to Cr(VI) values of 39, 50 and 53 mV pX(-1) for the sensors based on kraft, organosolv and lignosulphonate lignins, respectively, were observed. Redox sensitivity values close to the theoretical values of 20 and 21 mV pX(-1) for organosolv and lignosulphonate based sensors respectively were detected in the Cr(III)/Cr(VI) solutions while a very low response was observed in the solutions containing Fe(CN)(6)(3-/4-). Conducting composite lignin-based polyurethanes doped with MWCNTs were suggested as being promising materials for Cr(VI)-sensitive potentiometric sensors.

Microwaves and Ultrasound as Emerging Techniques for Lignocellulosic Materials.

Currently, in the context of biorefinery and bioeconomy, lignocellulosic biomass is increasingly used to produce biofuels, biochemicals and other value-added products. Microwaves and ultrasound are emerging techniques that enable efficient and environmentally sustainable routes in the transformation of lignocellulosic biomass. This review presents some of the most important works published in the last few years on the application of microwaves and/or ultrasound in lignocellulosic materials pretreatment and can be used as a starting point for research into this theme. This review is divided into four parts. In Part I, the theoretical fundamentals of microwave and ultrasound treatments are reviewed. Dielectric constants for biomass, factors that influence pretreatment, are some of the subjects addressed. In Part II, the effects that these techniques have on lignocellulosic biomass (on the size and surface area of the particle; on the content of lignin, hemicellulose and cellulose; on the crystallinity index of cellulose; on the effect of solubilization of organic matter; on hydrolysis and reduction of sugars) are discussed. In Part III, emphasis is given to the contribution of microwaves and ultrasound in obtaining value-added products. In this context, several examples of liquefaction and extraction procedures are presented. Part IV describes examples of performing sonocatalysis on lignocellulosic biomass to obtain value-added products, such as furfural, whose production is significantly reduced by ultrasound treatment.

Bio-Based Polyurethane Foams from Kraft Lignin with Improved Fire Resistance.

Rigid polyurethane foams (RPUFs) were synthesized using exclusively lignin-based polyol (LBP) obtained via the oxyalkylation of kraft lignin with propylene carbonate (PC). Using the design of experiments methodology combined with statistical analysis, the formulations were optimized to obtain a bio-based RPUF with low thermal conductivity and low apparent density to be used as a lightweight insulating material. The thermo-mechanical properties of the ensuing foams were compared with those of a commercial RPUF and a RPUF (RPUF-conv) produced using a conventional polyol. The bio-based RPUF obtained using the optimized formulation exhibited low thermal conductivity (0.0289 W/m·K), low density (33.2 kg/m3), and reasonable cell morphology. Although the bio-based RPUF has slightly lower thermo-oxidative stability and mechanical properties than RPUF-conv, it is still suitable for thermal insulation applications. In addition, the fire resistance of this bio-based foam has been improved, with its average heat release rate (HRR) reduced by 18.5% and its burn time extended by 25% compared to RPUF-conv. Overall, this bio-based RPUF has shown potential to replace petroleum-based RPUF as an insulating material. This is the first report regarding the use of 100% unpurified LBP obtained via the oxyalkylation of LignoBoost kraft lignin in the production of RPUFs.

Differentiation of isomeric pentose disaccharides by electrospray ionization tandem mass spectrometry and discriminant analysis.

RATIONALE: The structural characterization of unknown oligosaccharides remains a big challenge since a large number of isomeric structures are possible even for disaccharides. In this work, electrospray ionization collision-induced dissociation tandem mass spectrometry (ESI-CID-MS/MS) was used for the differentiation of isomeric pentose disaccharides, α-(1 → 5)-L-arabinobiose (Ara(2)) and ß-(1 → 4)-D-xylobiose (Xyl(2)). METHODS: ESI-MS/MS spectra of [M + Li](+) and [M + Na](+) ions of Ara(2) and Xyl(2), as well as these precursor ions of (18)O-labelled disaccharides, were acquired using two mass spectrometers equipped with different analyzers: LIT (linear ion trap) and Q-TOF (quadrupole time-of-flight). RESULTS: Product ions observed in MS/MS spectra arise from the cleavage at the nonreducing side of the glycosidic bond (Y(1)(+)) and from cross-ring cleavages (0,1)A(2)(+), (0,2)A(2)(+), and (0,3)A(2)(+) at the reducing residue. Statistically significant differences were observed between the relative abundance of specific product ions, when comparing both disaccharides. These differences allowed discriminant models to be built and to propose a criterion using the relative abundances of selected ions capable of discriminating between the isomers for both adduct ions and spectrometers. CONCLUSIONS: Isomeric pentose disaccharides can be distinguished based on the fragmentation of both [M + Li](+) and [M + Na](+) ions and using different mass spectrometers. However, LIT instrument has a better discriminant power.

Modified kraft lignin for bioremediation applications.

Kraft lignin (KL) from industrial pulping of E. globulus wood was subjected to the oxidative modification with the aim to produce sorbent mimicking humic matter for the bioremediation purposes. Lignin was oxidized by polyoxometalate Na(5)[PMo(10)V(2)O(40)] (POM), solely or in the presence of laccase, under pre-selected aerobic conditions (50-60°C, 1-2h, oxygen pressure 5 bar). The most pronounced lignin oxidation without its depolymerisation was observed in the reaction system POM/O(2). Modified lignins possessed increased amounts of COOH (up to 15 %) and CO (up to 500 %) groups, when compared to unmodified KL, and significantly higher molecular weights. Sorption capacity of KL before and after modification towards transition metals (cadmium (II) and mercury (II)) and triazine pesticide (atrazine) was assessed in batch experiments under equilibrium conditions. KL oxidation improved sorption capacity towards transition metals (up to 15 %) but not necessarily the uptake of atrazine that was higher for unmodified KL.

Improving the Industrial Practice of Reactive Washing of Cork Stoppers Using a Fractional Factorial Design.

Reactive washing (RW) is a key process for disinfecting, purifying, and bleaching of cork stoppers to seal bottles with alcoholic beverages. Excessively severe treatment conditions deteriorate the surface properties of cork stoppers and must be strictly controlled. In this study, the conventional RW of natural cork stoppers was optimized employing a fractional factorial design. The RW variables (H2O2 and NaOH concentrations, oxidation time, and washing water volume) were correlated with the final ISO brightness of the stoppers. A three-level and four-factor fractional factorial design within the response surface methodology approach allowed a quadratic model to predict the process response, where the H2O2 concentration is the variable with the highest response (ISO brightness), followed by the NaOH concentration. The model obtained was validated, allowing the optimization of the process with savings of 37% in the concentration of H2O2 and 33% in the concentration of NaOH and volume of washing water, without deteriorating the final appearance of the stoppers. In addition, the less severe treatment of stoppers under optimized conditions led to less degradation of their surface, thus favoring the receptivity to functional coatings.

Lignin as a Renewable Building Block for Sustainable Polyurethanes.

Currently, the pulp and paper industry generates around 50-70 million tons of lignin annually, which is mainly burned for energy recovery. Lignin, being a natural aromatic polymer rich in functional hydroxyl groups, has been drawing the interest of academia and industry for its valorization, especially for the development of polymeric materials. Among the different types of polymers that can be derived from lignin, polyurethanes (PUs) are amid the most important ones, especially due to their wide range of applications. This review encompasses available technologies to isolate lignin from pulping processes, the main approaches to convert solid lignin into a liquid polyol to produce bio-based polyurethanes, the challenges involving its characterization, and the current technology assessment. Despite the fact that PUs derived from bio-based polyols, such as lignin, are important in contributing to the circular economy, the use of isocyanate is a major environmental hot spot. Therefore, the main strategies that have been used to replace isocyanates to produce non-isocyanate polyurethanes (NIPUs) derived from lignin are also discussed.

Polyoxometalate Functionalized Sensors: A Review.

Polyoxometalates (POMs) are a class of metal oxide complexes with a large structural diversity. Effective control of the final chemical and physical properties of POMs could be provided by fine-tuning chemical modifications, such as the inclusion of other metals or non-metal ions. In addition, the nature and type of the counterion can also impact POM properties, like solubility. Besides, POMs may combine with carbon materials as graphene oxide, reduced graphene oxide or carbon nanotubes to enhance electronic conductivity, with noble metal nanoparticles to increase catalytic and functional sites, be introduced into metal-organic frameworks to increase surface area and expose more active sites, and embedded into conducting polymers. The possibility to design POMs to match properties adequate for specific sensing applications turns them into highly desirable chemicals for sensor sensitive layers. This review intends to provide an overview of POM structures used in sensors (electrochemical, optical, and piezoelectric), highlighting their main functional features. Furthermore, this review aims to summarize the reported applications of POMs in sensors for detecting and determining analytes in different matrices, many of them with biochemical and clinical relevance, along with analytical figures of merit and main virtues and problems of such devices. Special emphasis is given to the stability of POMs sensitive layers, detection limits, selectivity, the pH working range and throughput.

ß-Glucan-Functionalized Nanoparticles Down-Modulate the Proinflammatory Response of Mononuclear Phagocytes Challenged with Candida albicans.

Systemic fungal infections are associated with significant morbidity and mortality, and Candida albicans is the most common causative agent. Recognition of yeast cells by immune cell surface receptors can trigger phagocytosis of fungal pathogens and a pro-inflammatory response that may contribute to fungal elimination. Nevertheless, the elicited inflammatory response may be deleterious to the host by causing excessive tissue damage. We developed a nanoparticle-based approach to modulate the host deleterious inflammatory consequences of fungal infection by using ß1,3-glucan-functionalized polystyrene (ß-Glc-PS) nanoparticles. ß-Glc-PS nanoparticles decreased the levels of the proinflammatory cytokines TNF-α, IL-6, IL-1ß and IL-12p40 detected in in vitro culture supernatants of bone marrow-derived dendritic cells and macrophage challenged with C. albicans cells. Moreover, ß-Glc-PS nanoparticles impaired the production of reactive oxygen species by bone marrow-derived dendritic cells incubated with C. albicans. This immunomodulatory effect was dependent on the nanoparticle size. Overall, ß-Glc-PS nanoparticles reduced the proinflammatory response elicited by fungal cells in mononuclear phagocytes, setting the basis for a targeted therapy aimed at protecting the host by lowering the inflammatory cost of infection.

Modification of Paper Surface by All-Lignin Coating Formulations.

All-lignin coating formulations were prepared while combining water-soluble cationic kraft lignin (quaternized LignoBoost®, CL) and anionic lignosulphonate (LS). The electrostatic attraction between positively charged CL and negatively charged LS led to the formation of insoluble self-organized macromolecule aggregates that align to films. The structures of the formed layers were evaluated by atomic force microscopy (AFM), firstly on glass lamina using dip-coating deposition and then on handsheets and industrial uncoated paper using roll-to-roll coating in a layer-by-layer mode. Coated samples were also characterized by optical microscopy, scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (SEM/EDS), and contact angle measurements. It was suggested that the structure of all-lignin aggregates is the result of the interaction of amphiphilic water-soluble lignin molecules leading to their specifically ordered mutual arrangement depending on the order and the mode of their application on the surface. The all-lignin coating of cellulosic fiber imparts lower air permeability and lower free surface energy to paper, mainly due to a decrease in surface polarity, thus promoting the paper's hydrophobic properties. Moderate loading of lignin coating formulations (5-6 g m-2) did not affect the mechanical strength of the paper.

Polyurethane Adhesives Based on Oxyalkylated Kraft Lignin.

Lignin-based polyol was obtained via oxyalkylation reaction with propylene carbonate using eucalyptus kraft lignin isolated from the industrial cooking liquor by the Lignoboost® procedure. This lignin-based polyol (LBP) was used without purification in the preparation of polyurethane (PU) adhesives combined with polymeric 4,4'-methylenediphenyl diisocyanate (pMDI). A series of adhesives were obtained by varying the NCO/OH ratio of PU counterparts (pMDI and LBPs) and their performance was evaluated by gluing wood pieces under predefined conditions. The adhesion properties of the novel PU adhesive were compared with those of a commercial PU adhesive (CPA). The occurrence and extent of curing reactions and changes in the polymeric network of PA were monitored by Fourier transform infrared spectroscopy (FTIR) and dynamic mechanical analysis. Although the lap shear strength and glass transition temperature of the lignin-based PU adhesives have increased steadily with the NCO/OH ratio ranging from 1.1-2.2, chemical aging resistance can be compromised when the NCO/OH is very low. It was found that the lignin-based PU adhesive with an NCO/OH ratio of 1.3 showed better chemical resistance and adhesion efficiency than CPA possibly because the NCO/OH in the latter is too high as revealed by FTIR spectroscopy. Despite some lower thermal stability and shorter gelation time of lignin-based PU than CPA, the former revealed great potential to reduce the use of petroleum-derived polyols and isocyanates with potential application in the furniture industry as wood bonding adhesive.

Isolation and identification of an arabinogalactan extracted from pistachio external hull: Assessment of immunostimulatory activity.

This work studies the extraction and purification of a novel arabinogalactan from pistachio external hull. It was extracted with a simple method from pistachio hull which is considered as unexploited waste. Based on the results of sugar analysis by GC-FID, glycosidic linkage by GC-MS, NMR spectroscopy, and molecular weight by Size Exclusion Chromatography, pistachio hull water soluble polysaccharides (PHWSP) were identified as a type II arabinogalactan (AG), with characteristic terminally linked α-Araf, (α1 â†’ 5)-Araf, (α1 â†’ 3,5)-Araf, terminally linked ß-Galp, (ß1 â†’ 6)-Galp, and (ß1 â†’ 3,6)-Galp. DEPT-135, HSQC, HMBC and COSY NMR data suggested the presence of (ß1 â†’ 3)-Galp mainly branched at O-6 with (ß1 â†’ 6)-Galp chains, α-Araf chains, and terminally linked α-Araf. These AG from pistachio external hulls showed in vitro stimulatory activity for B cells, suggesting their possible use as an immunological stimulant in nutraceutical and biomedical applications.