Structural and thermal characterization of hemicelluloses isolated by organic solvents and alkaline solutions from Tamarix austromongolica

Phytochemical and pharmacological properties of the genus Tamarix: a comprehensive review

The genus Tamarix in the Tamaricaceae family consists of more than 100 species of halophyte plants worldwide that are mainly used to improve saline-alkali land and for coastal windbreaks, sand fixation, and afforestation in arid areas. A considerable number of species in this genus are also used as traditional medicines to treat various human diseases, especially in Asian and African countries. This review presents a comprehensive summary of 655 naturally occurring compounds derived from the genus Tamarix, categorized into flavonoids (18.0%), phenols (13.9%), tannins (9.3%), terpenoids (10.5%), essential oils (31.0%), and others (17.3%). The investigation revealed that the crude extracts and phytochemicals of this genus exhibited significant therapeutic potential, including anti-inflammatory, anti-Alzheimer, anticancer, antidiabetic, antibacterial, and antifungal activities. Six species of Tamarix have anticancer effects by causing cancer cell death, inducing autophagy, and stopping cell division. Seven species from the same genus have the potential for treating diabetes by inhibiting α-glycosidase activity, suppressing human islet amyloid polypeptide, regulating blood glucose levels, and modulating autophagy or inflammation. The focus on antibacterial and antidiabetic effects is due to the presence of volatile oil and flavonoid components. Extensive research has been conducted on the biological activity of 30 constituents, including 15 flavonoids, 5 phenols, 3 terpenoids, 1 tannin, and 6 others. Therefore, future research should thoroughly study the mechanisms of action of these and similar compounds. This is the most comprehensive review of the phytochemistry and pharmacological properties of Tamarix species, with a critical assessment of the current state of knowledge.

Polyaniline-coated kapok fibers for convenient in-syringe solid-phase microextraction and determination of organochlorine and pyrethroid pesticide residues in aqueous samples

Pesticides used in agriculture have low polarity and a tendency to accumulate in fatty tissues, posing potential risks to human health. Effective pre-treatment is crucial due to complex sample matrices and low concentrations of pesticide residues typically encountered in instrument analysis. In this study, polyaniline-coated kapok fiber (PANI-KF) was synthesized successfully using in-situ oxidative polymerization for use as sorbents in in-syringe SPME of pyrethroid pesticides (PYRs) and organochlorine pesticides (OCPs) from aqueous samples. Coating the natural KF with PANI maintained the hollow microtubular structure and fiber morphology while significantly enhancing the extraction efficiency. The extraction process was easily conducted by simply pulling and pushing the syringe plunger. The entire extraction process, utilizing 3 mg of PANI-KF, could be completed in approximately 3 min. Density functional theory results indicated that the adsorption mechanism of PANI-KF towards OCPs and PYRs mainly involved van der Waals interactions, π-π interactions, and weak hydrogen bonding interactions. With the coupling of gas chromatography-mass spectrometry, a quantification method was established that exhibited good linearities (R2 > 0.990), and relative recoveries (87.2-108.5 %). The limits of detection ranged from 0.4 to 2.0 ng mL-1 and the matrix effects were negligible (-12.3-16.4 %). The validated in-syringe SPME-GC-MS method was successfully applied to determine pesticide residues in fruit juices, oral liquids and herbal extract granules with satisfactory accuracy and precision. PANI-KF exhibits remarkable promise as a sorbent for the extraction and enrichment of pesticide residues in aqueous samples, thereby contributing to the advancement of pesticide residue determination methodologies.

Biotransformation of lignocellulosic biomass into industrially relevant products with the aid of fungi-derived lignocellulolytic enzymes

Lignocellulosic material has drawn significant attention among the scientific community due to its year-round availability as a renewable resource for industrial consumption. Being an economic substrate alternative, various industries are reevaluating processes to incorporate derived compounds from these materials. Varieties of fungi and bacteria have the ability to depolymerize lignocellulosic biomass by synthesizing degrading enzymes. Owing to catalytic activity stability and high yields of conversion, lignocellulolytic enzymes derived from fungi currently have a high spectrum of industrial applications. Moreover, these materials are cost effective, eco-friendly and nontoxic while having a low energy input. Techno-economic analysis for current enzyme production technologies indicates that synthetic production is not commercially viable. Instead, the economic projection of the use of naturally-produced ligninolytic enzymes is promising. This approach may improve the economic feasibility of the process by lowering substrate expenses and increasing lignocellulosic by-product's added value. The present review will discuss the classification and enzymatic degradation pathways of lignocellulolytic biomass as well as the potential and current industrial applications of the involved fungal enzymes.

Acacia Xylan as a Substitute for Commercially Available Xylan and Its Application in the Production of Xylooligosaccharides

Over the past two decades, birchwood and beechwood xylans have been used as a popular substrate for the characterization of xylanases. Recently, major companies have discontinued their commercial production. Therefore, there is a need to find an alternative to these substrates. Xylan extraction from Acacia sawdust resulted in 23.5% (w/w) yield. The extracted xylan is composed of xylose and glucuronic acid residues in a molar ratio of 6:1 with a molecular mass of ∼70 kDa. The specific optical rotation analysis of extracted xylan displayed that it is composed of the d-form of xylose and glucuronic acid monomeric sugars. The nuclear magnetic resonance analysis of extracted xylan revealed that the xylan backbone is substituted with 4-O-methyl glucuronic acid at the O2 position. Fourier transform infrared analysis confirmed the absence of lignin contamination in the extracted xylan. Xylanase from Clostridium thermocellum displayed the enzyme activity of 1761 U/mg against extracted xylan, and the corresponding activity against beechwood xylan was 1556 U/mg, which confirmed that the extracted xylan could be used as an alternative substrate for the characterization of xylanases.

Glycan utilisation system in Bacteroides and Bifidobacteria and their roles in gut stability and health

Gut residential hundred trillion microbial cells are indispensable for maintaining gut homeostasis and impact on host physiology, development and immune systems. Many of them have displayed excellence in utilising dietary- and host-derived complex glycans and are producing useful postbiotics including short-chain fatty acids to primarily fuel different organs of the host. Therefore, employing individual microbiota is nowadays becoming a propitious target in biomedical for improving gut dysbiosis conditions of the host. Among other gut microbial communities, Bacteroides and Bifidobacteria are coevolved to utilise diverse ranges of diet- and host-derived glycans through harmonising distinct glycan utilisation systems. These gut symbionts frequently share digested oligosaccharides, carbohydrate-active enzymes and fermentable intermediate molecules for sustaining gut microbial symbiosis and improving fitness of own or other communities. Genomics approaches have provided unprecedented insights into these functions, but their precise mechanisms of action have poorly known. Sympathetic glycan-utilising strategy of each gut commensal will provide overview of mechanistic dynamic nature of the gut environment and will then assist in applying aptly personalised nutritional therapy. Thus, the review critically summarises cutting edge understanding of major plant- and host-derived glycan-utilising systems of Bacteroides and Bifidobacteria. Their evolutionary adaptation to gut environment and roles of postbiotics in human health are also highlighted.

Thermal pyrolysis characteristics and kinetics of hemicellulose isolated from Camellia Oleifera Shell

Camellia Oleifera Shell (COS) is a kind of renewable lignocellulose resource and contains abundant hemicelluloses. In this work, the hemicelluloses in COS were extracted by alkali treatment and precipitated by ethanol with different concentration. Thermal pyrolysis kinetics of COS hemicelluloses were investigated using a thermogravimetric analyzer at the heating rates of 5, 10, and 20 °C/min based on Coats-Redfern, Flynn-Wall-Ozawa (FWO), and Kissinger-Akahira-Sunose (KAS) model. The results showed that the best fitting thermal pyrolysis mechanism of COS hemicelluloses was one-dimensional diffusion reaction analyzed by Coats-Redfern model. The activation energies of COS hemicelluloses ranged from 175.07 to 247.87 kJ·mol^-1 and from 174.74 to 252.50 kJ·mol^-1 calculated by FWO and KAS, respectively. The thermal stabilities of COS hemicelluloses were enhanced with the precipitated ethanol concentration increasing, and reflected by thermodynamic parameters ΔH, ΔG and ΔS. This study may provide basic theoretical supports for the thermochemical conversion of COS hemicelluloses.

Enzymatic production of xylooligosaccharides from Brazilian Syrah grape pomace flour: a green alternative to conventional methods for adding value to agricultural by- products

BACKGROUND

The aim of this work was to determine the most favorable conditions for the production of xylooligosaccharides (XOS) from Brazilian Syrah grape pomace. Chemical processes were performed using a rotatable central composite design where the concentration of sulfuric acid or sodium hydroxide and the grape pomace flour/solvent mass ratio were the dependent variables. Enzymatic production was also evaluated using xylanase produced by Aspergillus niger 3T5B8 and Viscozyme^® enzymatic commercial cocktail.

RESULTS

Chemical extraction allowed to recover 21.8-74.6% and 5.2-96.3% of total XOS for acidic and alkaline processes respectively. Enzymatic production extracted up to 88.68 ± 0.12% of total XOS using xylanase and up to 84.09 ± 2.40% with Viscozyme^® .

CONCLUSION

The present study demonstrated different feasible methods to produce high-added-value molecules, i.e. XOS, from Syrah grape pomace flour, valorizing this major by-product. The use of enzymatic cocktails demonstrated to be an alternative to the conventional methods, allowing to obtain an eco-friendly and sustainable grape pomace extract. © 2018 Society of Chemical Industry.

Biochemistry of complex glycan depolymerisation by the human gut microbiota

The human gut microbiota (HGM) makes an important contribution to health and disease. It is a complex microbial community of trillions of microbes with a majority of its members represented within two phyla, the Bacteroidetes and Firmicutes, although it also contains species of Actinobacteria and Proteobacteria. Reflecting its importance, the HGM is sometimes referred to as an 'organ' as it performs functions analogous to systemic tissues within the human host. The major nutrients available to the HGM are host and dietary complex carbohydrates. To utilise these nutrient sources, the HGM has developed elaborate, variable and sophisticated systems for the sensing, capture and utilisation of these glycans. Understanding nutrient acquisition by the HGM can thus provide mechanistic insights into the dynamics of this ecosystem, and how it impacts human health. Dietary nutrient sources include a wide variety of simple and complex plant and animal-derived glycans most of which are not degraded by enzymes in the digestive tract of the host. Here we review how various adaptive mechanisms that operate across the major phyla of the HGM contribute to glycan utilisation, focusing on the most complex carbohydrates presented to this ecosystem.

Microwave-Hydrothermal Rapid Synthesis of Cellulose/Ag Nanocomposites and Their Antibacterial Activity

Silver-based antimicrobial nanomaterials are considered as the most promising antibacterial agents owing to their outstanding antimicrobial efficacy and their relatively low toxicity to human beings. In this work, we report on a facile and environment-friendly microwave-hydrothermal method to prepare cellulose/Ag nanocomposites using hemicellulose as the reductant. The influences of the microwave-hydrothermal heating time and temperature, as well as the hemicellulose concentration on the formation of cellulose nanocomposites, were investigated in detail. Experimental results indicated that the hemicellulose was an effective reductant for silver ions, with higher temperature and longer heating time favoring the formation of silver with higher crystallinity and mass content in the nanocomposites. Moreover, the antimicrobial properties of the as-prepared cellulose/Ag nanocomposites were explored using Gram-positive S. aureus ATCC 6538 and Gram-negative E. coli HB 101 by both disc diffusion method and agar dilution method, and the nanocomposites showed excellent antibacterial activity. These results demonstrate that the as-prepared cellulose/Ag nanocomposites, as a kind of antibacterial material, are promising for applications in a wide range of biomedical fields.

Effects of Organosolv Pretreatment Using Temperature-Controlled Bench-Scale Ball Milling on Enzymatic Saccharification of Miscanthus × giganteus

The effect of organosolv pretreatment was investigated using a 30 L bench-scale ball mill reactor that was capable of simultaneously performing physical and chemical pretreatment. Various reaction conditions were tried in order to discover the optimal conditions for the minimal cellulose loss and enhanced enzymatic digestibility of Miscanthus × giganteus (MG), with conditions varying from room temperature to 170 °C for reaction temperature, from 30 to 120 min of reaction time, from 30% to 60% ethanol concentration, and a liquid/solid ratio (L/S) of 10–20 under non-catalyst conditions. The pretreatment effects were evaluated by chemical compositional analysis, enzymatic digestibility test and X-ray diffraction of the treated samples. The pretreatment conditions for the highest glucan digestibility yield were determined as 170 °C, reaction time of 90 min, ethanol concentration of 40% and L/S = 10. With these pretreatment conditions, the XMG (xylan + mannan + galactan) fractionation yield and delignification were 84.4% and 53.2%, respectively. The glucan digestibility of treated MG after the aforementioned pretreatment conditions was 86.0% with 15 filter paper units (FPU) of cellulase (Cellic® CTec2) per g-glucan enzyme loading.

Effects of alkaline catalysts on acetone-based organosolv pretreatment of rice straw

Organosolv is an effective pretreatment strategy for increasing digestibility of lignocellulosic materials owing to selectivity of solvents on separating biopolymeric constituents of plant biomass. In the present work, a novel low-temperature alkali-catalyzed organosolv pretreatment of rice straw was studied. The effects of alkaline catalysts (i.e., NaOH, ammonia, and tri-ethylamine) and solvent types (i.e., acetone, ethanol, and water) were carried out. Addition of alkalis led to increasing sugar from enzymatic hydrolysis while acetone was found to be superior to ethanol and water on selectivity towards cellulose preservation. The optimal alkaline-catalyzed pretreatment reaction contained 5% (w/v) NaOH in an aqueous-acetone mixture (1:4) at 80 °C for 5 min. A glucose yield of 913 mg/g of pretreated biomass was achieved, equivalent to a maximal glucose recovery of 93.0% from glucan in the native biomass. Scanning electron microscope revealed efficient removal of non-cellulosic components, resulting in exposed cellulose microfibers with a reduced crystallite size as determined by X-ray diffraction. With potential on obtaining high-quality lignin, the work demonstrated potential of the novel low-temperature alkaline-catalyzed acetone-based organosolv process for pretreatment of lignocellulosic materials in biorefineries.

Pretreatment of eucalyptus with recycled ionic liquids for low-cost biorefinery

It is urgent to develop recycled ionic liquids (ILs) as green solvents for sustainable biomass pretreatment. The goal of this study is to explore the availability and performance of reusing 1-allyl-3-methylimidazolium chloride ([amim]Cl) and 1-butyl-3-methylimidazolium acetate ([bmim]OAc) for pretreatment, structural evolution, and enzymatic hydrolysis of eucalyptus. Cellulose enzymatic digestibility slightly decreased with the increased number of pretreatment recycles. The hydrolysis efficiencies of eucalyptus pretreated via 4th recycled ILs were 54.3% for [amim]Cl and 72.8% for [bmim]OAc, which were 5.0 and 6.7-folds higher than that of untreated eucalyptus. Deteriorations of ILs were observed by the relatively lower sugar conversion and lignin removal from eucalyptus after 4th reuse. No appreciable changes in fundamental framework and thermal stability of [amim]Cl were observed even after successive pretreatments, whereas the anionic structure of [bmim]OAc was destroyed or replaced. This study suggested that the biomass pretreatment with recycled ILs was a potential alternative for low-cost biorefinery.

Organic amine catalytic organosolv pretreatment of corn stover for enzymatic saccharification and high-quality lignin

A novel and efficient organic amine and organosolv synergetic pretreatment method was developed to overcome the recalcitrance of lignocellulose to produce fermentable sugars and high-quality salt-free lignin. After optimization of the process parameters, a delignification of 81.7% and total sugar yield of 83.2% (87.1% glucose, 75.4% xylose) could be obtained using n-propylamine (10mmol/g, biomass) as a catalyst and aqueous ethanol (60%, v/v) as a solvent. The susceptibility of the substrates to enzymatic digestibility was explained by their physical and chemical characteristics. The physical structure of extracted lignin showed higher β-aryl ether bonds content and functionalities, offering the potential for further downstream upgrading. The role of organic amine catalyst and a synergistic mechanism is proposed for the present system.

Bacterial xylanases: biology to biotechnology

In this review, a comprehensive discussion exclusively on bacterial xylanases; their gene organization; different factors and conditions affecting enzyme yield and activity; and their commercial application have been deliberated in the light of recent research findings and extensive information mining. Improved understanding of biological properties and genetics of bacterial xylanase will enable exploitation of these enzymes for many more ingenious biotechnological and industrial applications.

Organic solvent pretreatment of lignocellulosic biomass for biofuels and biochemicals: A review

Lignocellulosic biomass represents the largest potential volume and lowest cost for biofuel and biochemical production. Pretreatment is an essential component of biomass conversion process, affecting a majority of downstream processes, including enzymatic hydrolysis, fermentation, and final product separation. Organic solvent pretreatment is recognized as an emerging way ahead because of its inherent advantages, such as the ability to fractionate lignocellulosic biomass into cellulose, lignin, and hemicellulose components with high purity, as well as easy solvent recovery and solvent reuse. Objectives of this review were to update and extend previous works on pretreatment of lignocellulosic biomass for biofuels and biochemicals using organic solvents, especially on ethanol, methanol, ethylene glycol, glycerol, acetic acid, and formic acid. Perspectives and recommendations were given to fully describe implementation of proper organic solvent pretreatment for future research.

Production of xylooligosaccharides from hardwood xylan by using immobilized endoxylanase of Clostridium strain BOH3

Endoxylanase ofClostridiumsp. BOH3 was immobilized in calcium alginate/silica gel matrix with a 100% yield. This immobilized xylanase can be reused 7 times to produce prebiotic xylooligosaccharides from hardwood xylan with 62% of activity recovery.

Ultrasound-assisted extraction of hemicelluloses from grape pomace using response surface methodology

An ultrasound-assisted procedure was applied to the extraction of hemicelluloses from grape pomace at a mild temperature (20°C). A Central composite design (CCD) was employed to optimize the ultrasound-assisted extraction (UAE) of hemicelluloses from grape pomace with the aim to maximize their extraction yield, and, also, the obtention of the main polymers forming this fraction: Xyloglucans (XLG), Mannans (MAN) and Xylans (XN). Extraction time (X1), solid:liquid ratio (X2) and KOH concentration (X3) were the variables used to optimize the process. The conditions that maximize (1) the extraction yield of hemicelluloses and the contents of (2) XLG, (3) MAN and (4) XN, were: (1) X1=2.6h; X2=1:48 (w/v); X3=0.4M, (2) X1=2.9h; X2=1:57 (w/v); X3=2.25M, (3) X1=2.7h; X2=1:58(w/v);X3=2.2M, and (4) X1=3h; X2=1:60 (w/v); X3=2.3M, respectively. Under these conditions, the maximum extraction yield of hemicelluloses, XLG, MAN and XN contents were: ∼7.9±0.2%, ∼3.6±0.02%, ∼1.1±0.04% and ∼1.2±0.02%, respectively. Close agreement between experimental and predicted values was found. The results suggest that the ultrasound-assisted extraction could be a good option for the extraction of hemicellulosic polysaccharides from grape pomace at industrial level.

Methylation--an uncommon modification of glycans

A methyl (Me) group on a sugar residue is a rarely reported event. Until now, this type of modification has been found in the animal kingdom only in worms and molluscs, whereas it is more frequently present in some species of bacteria, fungi, algae and plants, but not in mammals. The monosaccharides involved as well as the positions of the Me groups on the sugar vary with species. Methylation appears to play a role in some recognition events, but details are still unknown. This review summarises the current knowledge on methylation of sugars in all types of organism.

The structural changes of the bagasse hemicelluloses during the cooking process involving active oxygen and solid alkali

This work describes the structural changes of bagasse hemicelluloses during the cooking process involving active oxygen (O(2) and H(2)O(2)) and solid alkali (MgO). The hemicelluloses obtained from the bagasse raw material, pulp, and yellow liquor were analyzed by high-performance anion-exchange chromatography (HPAEC), gel permeation chromatography (GPC), Fourier transform infrared spectroscopy (FT-IR), and (1)H-(13)C 2D hetero-nuclear single quantum coherence spectroscopy (HSQC). The results revealed that the structure of the bagasse hemicelluloses was L-arabino-(4-O-methylglucurono)-D-xylan. Some sugar units in hemicelluloses were oxidized under the cooking conditions. Additionally, the backbones and the ester linkages of hemicelluloses were heavily cleaved during the cooking process.