Structural characterization of corn fiber hemicelluloses extracted by organic solvent and screening of degradation enzymes.

An integrated treatment coupling peracetic acid delignification, dimethyl sulfoxide extraction, and ethanol precipitation were performed to isolate hemicellulose from de-starched corn fiber. Based on chemical composition, molecular weight distribution, methylation, and nuclear magnetic resonance spectroscopy, it is proposed that hemicelluloses in corn fiber were composed of two polysaccharides, glucuronoarabinoxylan (about 80 %) and xyloglucan (about 20 %). Xylose (about 46 %) and arabinose (about 32 %) were the main components in glucuronoarabinoxylan. More than half of the xylose units in the glucuronoarabinoxylan backbone chain were substituted at O-2 and/or O-3 by various monomers or oligomeric side chains. Based on structure analysis, five hemicellulases were selected and added to Penicillium oxalicum MCAX enzymes for enzymatic hydrolysis of corn fiber. The results showed that the addition of hemicellulases increased the sugar yield of corn fiber. These results demonstrate the effectiveness of enzyme consortium constructed by elucidating the chemical structure of hemicellulose in corn fiber for the degradation of corn fiber and also provide a general solution for the rational construction of targeted and efficient enzyme systems for the degradation of lignocellulosic biomass.

Willow Bark-Derived Material with Antibacterial and Antibiofilm Properties for Potential Wound Dressing Applications.

Tree stems contain wood in addition to 10-20% bark, which remains one of the largest underutilized biomasses on earth. Unique macromolecules (like lignin, suberin, pectin, and tannin), extractives, and sclerenchyma fibers form the main part of the bark. Here, we perform detailed investigation of antibacterial and antibiofilm properties of bark-derived fiber bundles and discuss their potential application as wound dressing for treatment of infected chronic wounds. We show that the yarns containing at least 50% of willow bark fiber bundles significantly inhibit biofilm formation by wound-isolated Staphylococcus aureus strains. We then correlate antibacterial effects of the material to its chemical composition. Lignin plays the major role in antibacterial activity against planktonic bacteria [i.e., minimum inhibitory concentration (MIC) 1.25 mg/mL]. Acetone extract (unsaturated fatty acid-enriched) and tannin-like (dicarboxylic acid-enriched) substances inhibit both bacterial planktonic growth [MIC 1 and 3 mg/mL, respectively] and biofilm formation. The yarn lost its antibacterial activity once its surface lignin reached 20.1%, based on X-ray photoelectron spectroscopy. The proportion of fiber bundles at the fabricated yarn correlates positively with its surface lignin. Overall, this study paves the way to the use of bark-derived fiber bundles as a natural-based material for active (antibacterial and antibiofilm) wound dressings, upgrading this underappreciated bark residue from an energy source into high-value pharmaceutical use.

In Situ Adsorption of Red Onion (Allium cepa) Natural Dye on Cellulose Model Films and Fabrics Exploiting Chitosan as a Natural Mordant.

Synthetic dyes and chemicals create an enormous impact on environmental pollution both in textile manufacturing and after the product's lifetime. Biobased plant-derived colorants and mordants have great potential for the development of more sustainable textile dyeing processes. Colorants isolated from biomass residues are renewable, biodegradable, and usually less harmful than their synthetic counterparts. Interestingly, they may also bring additional functions to the materials. However, the extraction and purification of the biocolorants from biomass as well as their dyeing efficiency and color fastness properties require a more thorough examination. Here, we extracted red onion (Allium cepa) skins to obtain polyphenolic flavonoids and anthocyanins as biocolorants, characterized the chemical composition of the mixture, and used a quartz crystal microbalance and thin films of cellulose nanofibrils to study the adsorption kinetics of dyes onto cellulose substrates in situ. The effect of different mordants on the adsorption behavior was also investigated. Comparison of these results with conventional dyeing experiments of textiles enabled us to determine the interaction mechanism of the dyes with substrates and mordants. Chitosan showed high potential as a biobased mordant based both on its ability to facilitate fast adsorption of polyphenols to cellulose and its ability to retain the purple color of the red onion dye (ROD) in comparison to the metal mordants FeSO4 and alum. The ROD also showed excellent UV-shielding efficiency at low concentrations, suggesting that biocolorants, due to their more complex composition compared to synthetic ones, can have multiple actions in addition to providing aesthetics.

Effect of Hybrid Type and Harvesting Season on Phytochemistry and Antibacterial Activity of Extracted Metabolites from Salix Bark.

Hundreds of different fast-growing Salix hybrids have been developed mainly for energy crops. In this paper, we studied water extracts from the bark of 15 willow hybrids and species as potential antimicrobial additives. Treatment of ground bark in water under mild conditions extracted 12-25% of the dry material. Preparative high-performance liquid chromatography is proven here as a fast and highly efficient tool in the small-scale recovery of raffinose from Salix bark crude extracts for structural elucidation. Less than half of the dissolved material was assigned by chromatographic (gas chromatography and liquid chromatography) and spectroscopic (mass spectrometry and nuclear magnetic resonance spectroscopy) techniques for low-molecular-weight compounds, including mono- and oligosaccharides (sucrose, raffinose, and stachyose) and aromatic phytochemicals (triandrin, catechin, salicin, and picein). The composition of the extracts varied greatly depending on the hybrid or species and the harvesting season. This information generated new scientific knowledge on the variation in the content and composition of the extracts between Salix hybrids and harvesting season depending on the desired molecule. The extracts showed high antibacterial activity on Staphylococcus aureus with a minimal inhibitory concentration (MIC) of 0.6-0.8 mg/mL; however, no inhibition was observed against Escherichia coli, Enterococcus faecalis, and Salmonella typhimurium. MIC of triandrin (i.e., 1.25 mg/mL) is reported for the first time. Although antibacterial triandrin and (+)-catechin were present in extracts, clear correlation between the antibacterial effect and the chemical composition was not established, which indicates that antibacterial activity of the extracts mainly originates from some not yet elucidated substances. Aquatic toxicity and mutagenicity assessments showed the safe usage of Salix water extracts as possible antibacterial additives.

Structural Elucidation of Suberin from the Bark of Cultivated Willow (Salix sp.).

Although extractives have been symbolized as major bioactive pharmacological compounds from Salix (Salicaceae) bark, we speculated that these pharmaceutical effects cannot be solely attributed to phenolic components and their derivatives, but the long-chain suberin acids also contribute to their therapeutic effects. Hence, isolation and deconstruction of suberin were conducted, for the first time, to enrich our knowledge about the macromolecular components at the cell wall of willow bark. Saponification was adopted to obtain suberin extracts at a yield of approximately 5 wt % based on the bark of the studied hybrids. Gas chromatography-mass spectrometry allowed qualification and quantification of 23 compounds from the released suberin monomers, from which fatty acids represented majority of the isolated suberin, namely, fatty acid methyl esters (C17-C19); mono-carboxylic acid (C7-C16); alpha, omega-dicarboxylic acid (C7-C16); and omega-hydroxy long-chain fatty acids (C16-C22). Additionally, the lipophilic extractive was dominated by piceol, heptacosane, ß-sitosterol, and fatty acids (C16-C28) from the studied hybrids. These findings could boost our integrative approach toward full valorization of willow bark.

Salix spp. Bark Hot Water Extracts Show Antiviral, Antibacterial, and Antioxidant Activities-The Bioactive Properties of 16 Clones.

Earlier studies have shown that the bark of Salix L. species (Salicaceae family) is rich in extractives, such as diverse bioactive phenolic compounds. However, we lack knowledge on the bioactive properties of the bark of willow species and clones adapted to the harsh climate conditions of the cool temperate zone. Therefore, the present study aimed to obtain information on the functional profiles of northern willow clones for the use of value-added bioactive solutions. Of the 16 willow clones studied here, 12 were examples of widely distributed native Finnish willow species, including dark-leaved willow (S. myrsinifolia Salisb.) and tea-leaved willow (S. phylicifolia L.) (3 + 4 clones, respectively) and their natural and artificial hybrids (3 + 2 clones, respectively). The four remaining clones were commercial willow varieties from the Swedish willow breeding program. Hot water extraction of bark under mild conditions was carried out. Bioactivity assays were used to screen antiviral, antibacterial, antifungal, yeasticidal, and antioxidant activities, as well as the total phenolic content of the extracts. Additionally, we introduce a fast and less labor-intensive steam-debarking method for Salix spp. feedstocks. Clonal variation was observed in the antioxidant properties of the bark extracts of the 16 Salix spp. clones. High antiviral activity against a non-enveloped enterovirus, coxsackievirus A9, was found, with no marked differences in efficacy between the native clones. All the clones also showed antibacterial activity against Staphylococcus aureus and Escherichia coli, whereas no antifungal (Aspergillus brasiliensis) or yeasticidal (Candida albicans) efficacy was detected. When grouping the clone extract results into Salix myrsinifolia, Salix phylicifolia, native hybrid, artificial hybrid, and commercial clones, there was a significant difference in the activities between S. phylicifolia clone extracts and commercial clone extracts in the favor of S. phylicifolia in the antibacterial and antioxidant tests. In some antioxidant tests, S. phylicifolia clone extracts were also significantly more active than artificial clone extracts. Additionally, S. myrsinifolia clone extracts showed significantly higher activities in some antioxidant tests than commercial clone extracts and artificial clone extracts. Nevertheless, the bark extracts of native Finnish willow clones showed high bioactivity. The obtained knowledge paves the way towards developing high value-added biochemicals and other functional solutions based on willow biorefinery approaches.

Plant-Derived Natural Biomolecule Picein Attenuates Menadione Induced Oxidative Stress on Neuroblastoma Cell Mitochondria.

Several bioactive compounds are in use for the treatment of neurodegenerative disorders, such as Alzheimer's and Parkinson's disease. Historically, willow (salix sp.) bark has been an important source of salisylic acid and other natural compounds with anti-inflammatory, antipyretic and analgesic properties. Among these, picein isolated from hot water extract of willow bark, has been found to act as a natural secondary metabolite antioxidant. The aim of this study was to investigate the unrevealed pharmacological action of picein. In silico studies were utilized to direct the investigation towards the neuroprotection abilities of picein. Our in vitro studies demonstrate the neuroprotective properties of picein by blocking the oxidative stress effects, induced by free radical generator 2-methyl-1,4-naphthoquinone (menadione, MQ), in neuroblastoma SH-SY5Y cells. Several oxidative stress-related parameters were evaluated to measure the protection for mitochondrial integrity, such as mitochondrial superoxide production, mitochondrial activity (MTT), reactive oxygen species (ROS) and live-cell imaging. A significant increase in the ROS level and mitochondrial superoxide production were measured after MQ treatment, however, a subsequent treatment with picein was able to mitigate this effect by decreasing their levels. Additionally, the mitochondrial activity was significantly decreased by MQ exposure, but a follow-up treatment with picein recovered the normal metabolic activity. In conclusion, the presented results demonstrate that picein can significantly reduce the level of MQ-induced oxidative stress on mitochondria, and thereby plays a role as a potent neuroprotectant.

Willow Bark for Sustainable Energy Storage Systems.

Willow bark is a byproduct from forestry and is obtained at an industrial scale. We upcycled this byproduct in a two-step procedure into sustainable electrode materials for symmetrical supercapacitors using organic electrolytes. The procedure employed precarbonization followed by carbonization using different types of KOH activation protocols. The obtained electrode materials had a hierarchically organized pore structure and featured a high specific surface area (>2500 m2 g-1) and pore volume (up to 1.48 cm3 g-1). The assembled supercapacitors exhibited capacitances up to 147 F g-1 in organic electrolytes concomitant with excellent cycling performance over 10,000 cycles at 0.6 A g-1 using coin cells. The best materials exhibited a capacity retention of 75% when changing scan rates from 2 to 100 mV s-1.

Highly Porous Willow Wood-Derived Activated Carbon for High-Performance Supercapacitor Electrodes.

In this study, we present willow wood as a new low-cost, renewable, and sustainable biomass source for the production of a highly porous activated carbon for application in energy storage devices. The obtained activated carbon showed favorable features required for excellent electrochemical performance such as high surface area (∼2 800 m2 g-1) and pore volume (1.45 cm3 g-1), with coexistence of micropores and mesopores. This carbon material was tested as an electrode for supercapacitor application and showed a high specific capacitance of 394 F g-1 at a current density of 1 A g-1 and good cycling stability, retaining ∼94% capacitance after 5 000 cycles (at a current density of 5 A g-1) in 6 M KOH electrolyte. The prepared carbon material also showed an excellent rate performance in a symmetrical two-electrode full cell configuration using 1 M Na2SO4 electrolyte, in a high working voltage of 1.8 V. The maximum energy density and power density of the fabricated symmetric cell reach 23 W h kg-1 and 10 000 W kg-1, respectively. These results demonstrate that willow wood can serve as a low-cost carbon feedstock for production of high-performance electrode material for supercapacitors.

Structural Characterization of Lignins from Willow Bark and Wood.

Understanding the chemical structure of lignin in willow bark is an indispensable step to design how to separate its fiber bundles. The whole cell wall and enzyme lignin preparations sequentially isolated from ball-milled bark, inner bark, and wood were comparatively investigated by nuclear magnetic resonance (NMR) spectroscopy and three classical degradative methods, i.e., alkaline nitrobenzene oxidation, derivatization followed by reductive cleavage, and analytical thioacidolysis. All results demonstrated that the guaiacyl (G) units were predominant in the willow bark lignin over syringyl (S) and minor p-hydroxyphenyl (H) units. Moreover, the monomer yields and S/G ratio rose progressively from bark to inner bark and wood, indicating that lignin may be more condensed in bark than in other tissues. Additionally, major interunit linkage substructures (ß-aryl ethers, phenylcoumarans, and resinols) together with cinnamyl alcohol end groups were relatively quantitated by two-dimensional NMR spectroscopy. Bark and inner bark were rich in pectins and proteins, which were present in large quantities and also in the enzyme lignin preparations.

Rapid and near-complete dissolution of wood lignin at ≤80°C by a recyclable acid hydrotrope.

We report the discovery of the hydrotropic properties of a recyclable aromatic acid, p-toluenesulfonic acid (p-TsOH), for potentially low-cost and efficient fractionation of wood through rapid and near-complete dissolution of lignin. Approximately 90% of poplar wood (NE222) lignin can be dissolved at 80°C in 20 min. Equivalent delignification using known hydrotropes, such as aromatic salts, can be achieved only at 150°C or higher for more than 10 hours or at 150°C for 2 hours with alkaline pulping. p-TsOH fractionated wood into two fractions: (i) a primarily cellulose-rich water-insoluble solid fraction that can be used for the production of high-value building blocks, such as dissolving pulp fibers, lignocellulosic nanomaterials, and/or sugars through subsequent enzymatic hydrolysis; and (ii) a spent acid liquor stream containing mainly dissolved lignin that can be easily precipitated as lignin nanoparticles by diluting the spent acid liquor to below the minimal hydrotrope concentration. Our nuclear magnetic resonance analyses of the dissolved lignin revealed that p-TsOH can depolymerize lignin via ether bond cleavage and can separate carbohydrate-free lignin from the wood. p-TsOH has a relatively low water solubility, which can facilitate efficient recovery using commercially proven crystallization technology by cooling the concentrated spent acid solution to ambient temperatures to achieve environmental sustainability through recycling of p-TsOH.

Activation of TEMPO by ClO2 for oxidation of cellulose by hypochlorite-Fundamental and practical aspects of the catalytic system.

Bromide-free TEMPO-catalyzed oxidation of the primary alcohols by sodium hypochlorite (NaOCl) does not proceed without a prior activation of the catalyst. Here were demonstrate an immediate in situ activation of the catalyst with an equimolar addition of chlorine dioxide (ClO2) relative to TEMPO. Sodium bromide (NaBr) had a similar role in activating the catalyst although NaBr was needed in excess and the activation took several minutes depending on the dosage of NaBr. The activation method, or the concentration of NaBr, did not affect the bulk oxidation rate. The selectivity of the ClO2 initiated oxidation remained high up to NaOCl addition of 3mol/kg bleached birch kraft pulp after which additional loss in yield and depolymerization of cellulose were emphasized with negligible increase in carboxylate content. A carboxylate content of 0.8-1mol/kg, sufficient for easy mechanical fibrillation of the pulp, was achieved under mild conditions with NaOCl addition of 2-2.5mol/kg pulp.