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1.
Chem Commun (Camb) ; 55(76): 11346-11349, 2019 Sep 19.
Artigo em Inglês | MEDLINE | ID: mdl-31475702

RESUMO

Cellulose oligomers with a terminal alkyl group at the reducing end formed mechanically robust crystalline monolayers via self-assembly against water surfaces from aqueous solutions. The unique properties of the monolayers resulted in anisotropic deformation or manipulation of the aqueous solution droplets.


Assuntos
Celulose/química , Oligossacarídeos/química , Tensoativos/química , Água/química , Celulose/síntese química , Fenômenos Mecânicos , Tamanho da Partícula , Propriedades de Superfície
2.
J Agric Food Chem ; 67(39): 10880-10890, 2019 Oct 02.
Artigo em Inglês | MEDLINE | ID: mdl-31508956

RESUMO

A sustainable biomass-based nanocomposite hydrogel was formulated, characterized, and applied for curcumin delivery. Phytosynthesized zinc oxide nanoparticles (ZnO NPs) employing musk melon (Cucumis melo) seed extract was embedded in the hydrogel matrices and cross-linked using Dialdehyde cellulose prepared from sugarcane (Saccharum officinarum) bagasse (SCB). Nanoparticle incorporation enhanced the hydrogel's swelling degree to 4048% at pH 4.0. Also, an improved tensile strength of 14.1 ± 0.32 MPa was exhibited by the nanocomposite hydrogel compared to 9.79 ± 0.76 MPa for the pure chitosan cellulose hydrogel. A curcumin loading efficiency of 89.68% with around 30% increased loading was exhibited for the nanocomposite hydrogel. A Fickian diffusion-controlled curcumin release mechanism with maximum release at pH 7.4 was obtained. The synergistic effect on the antimicrobial activity was exhibited against Staphylococcus aureus and Trichophyton rubrum. The in vitro cytotoxicity studies employing L929 cells and A431 cells demonstrated good biocompatibility and enhanced anticancer activity of the curcumin-loaded green nanocomposite hydrogel compared to pure curcumin.


Assuntos
Anti-Infecciosos/química , Anti-Infecciosos/farmacologia , Curcumina/química , Curcumina/farmacologia , Sistemas de Liberação de Medicamentos/métodos , Extratos Vegetais/química , Extratos Vegetais/farmacologia , Celulose/química , Quitosana/química , Cucumis melo/química , Portadores de Fármacos/química , Hidrogéis/química , Nanocompostos/química , Nanopartículas/química , Sementes/química , Staphylococcus aureus/efeitos dos fármacos , Trichophyton/efeitos dos fármacos , Trichophyton/crescimento & desenvolvimento , Óxido de Zinco/química
3.
J Agric Food Chem ; 67(36): 10116-10125, 2019 Sep 11.
Artigo em Inglês | MEDLINE | ID: mdl-31442037

RESUMO

Pseudo-lignin is generated from lignocellulose biomass during pretreatment with dilute sulfuric acid and has a significant inhibitory effect on cellulase. However, the mechanism of pseudo-lignin generation remains unclear. The following main points have been addressed to help elucidate the pseudo-lignin generation pathway. Cellulose and xylan were pretreated with sulfuric acid at different concentrations; aliquots were periodically collected; and the changes in the byproducts of the prehydrolysate were quantified. Milled wood lignin (MWL) mixed with cellulose and xylan was pretreated to evaluate the impact of lignin on pseudo-lignin generation. Furfural, 5-hydroxymethylfurfural, and MWL were pretreated as model compounds to investigate pseudo-lignin generation. The result indicated that the increasing acid concentration significantly promoted the generation of pseudo-lignin. When the acid concentration was increased from 0 to 1.00 wt %, pseudo-lignin was increased from 1.36 to 4.05 g. In addition, lignin promoted the pseudo-lignin generation through the condensation between lignin and the generated intermediates.


Assuntos
Lignina/química , Saccharum/química , Ácidos Sulfúricos/análise , Biotecnologia , Celulose/química , Hidrólise , Madeira/química
4.
J Agric Food Chem ; 67(39): 10954-10967, 2019 Oct 02.
Artigo em Inglês | MEDLINE | ID: mdl-31365242

RESUMO

High-performance and useful graphene oxide (GO) and cellulose nanocrystals (CNCs) are easily extracted from natural graphite and cellulose raw materials, and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) is produced by bacterial fermentation from natural plant corn stalks, etc. In this study, novel ternary nanocomposites consisting of PHBV/cellulose nanocrystal-graphene oxide nanohybrids were prepared via a simple solution casting method. The synergistic effect of CNC with GO nanohybrids obtained by chemical grafting (CNC-GO, covalent bonds) and physical blending (CNC/GO, noncovalent bonds) on the physicochemical properties of PHBV nanocomposites was evaluated and the results compared with a single component nanofiller (CNC or GO) in binary nanocomposites. More interestingly, ternary nanocomposites displayed the highest thermal stability and mechanical properties. Compared to neat PHBV, the tensile strength and elongation to break increased by 170.2 and 52.1%, respectively, and maximum degradation temperature (Tmax) increment by 26.3 °C, were observed for the ternary nanocomposite with 1 wt % covalent bonded CNC-GO. Compared to neat PHBV, binary, and 1:0.5 wt % noncovalent CNC/GO based nanocomposites, the ternary nanocomposites with 1 wt % covalent bonded CNC-GO exhibited excellent barrier properties, good antibacterial activity (antibacterial ratio of 100.0%), reduced barrier properties, and lower migration level for both food simulants. Such a synergistic effect yielded high-performance ternary nanocomposites with great potential for bioactive food packaging materials.


Assuntos
Celulose/química , Embalagem de Alimentos/instrumentação , Grafite/química , Nanocompostos/química , Nanopartículas/química , Poliésteres/química , Celulose Oxidada , Temperatura Ambiente , Resistência à Tração
5.
Bioresour Technol ; 291: 121839, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31376673

RESUMO

Inorganic salt treatment is a novel, high-yield, and environmentally friendly approach for the production of xylo-oligosaccharides from Sugarcane bagasse with degree of polymerization of 2-5. A xylo-oligosaccharides yield of 53.79% was obtained with 0.1 M MgCl2 treatment at 180 °C/10 min, and 41.89% with 0.1 M FeCl2 treatment at 140 °C/30 min. The xylo-oligosaccharides yield from the co-catalysis of 0.05 M FeCl2 + 0.05 M MgCl2 reached 54.68% (29.34% xylobiose and 20.94% xylotriose) at 140 °C/30 min. The co-catalysis not only effectively improved the xylobiose and xylotriose contents but also increased the total yield of xylo-oligosaccharides under mild reaction conditions. Additionally, the glucose yield observed from the solid residue after inorganic salt treatment was 71.62% by enzymatic hydrolysis. Mg2+ and Fe2+ are essential for good human health without separation from the system, therefore, the inorganic salt treatment can be potentially applied in the co-production of xylo-oligosaccharides and glucose.


Assuntos
Celulose/química , Compostos Ferrosos/química , Cloreto de Magnésio/química , Oligossacarídeos/química , Saccharum/química , Catálise , Glucose/química , Hidrólise , Polimerização
6.
Bioresour Technol ; 291: 121842, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31377505

RESUMO

The spherical cellulose nanocrystals (CNCs) with high purity were prepared, the processes included composite enzymolysis of pulp fibers and the purification of product. The impurities in the crude product CNCs were analyzed with FTIR, coomassie brilliant blue-G250 and ionic chromatography. The pure CNCs were characterized with SEM, XRD, DLS and TGA. The results indicated that the crude CNCs was flocculated and washed twice with a dilute acid solution (pH = 2) to get pure spherical CNCs, the purity was approximate 99.99%. The obtained pure spherical CNCs had a narrow particle size distribution with diameter 15-40 nm. FTIR and XRD analyses proved that the crystal phase of the spherical CNCs did not change, but the crystallinity decreased slightly compared with pulp fibers. The thermal degradation showed that the spherical CNCs had better thermal stability than one from other methods, and the temperature of maximum weight loss rate (Tmax) was 329.2 °C.


Assuntos
Celulose/química , Nanopartículas/química , Temperatura Alta , Papel , Espectroscopia de Infravermelho com Transformada de Fourier
7.
Bioresour Technol ; 291: 121844, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31400704

RESUMO

A low-temperature sodium hydroxide (NaOH) pretreatment for sugarcane bagasse (SCB) was obtained via the surface response design in this study. However, a large quantity of water consumption and wastewater generation which have been the common problems for alkaline pretreatment of lignocellulose still exists in this pretreatment. In order to reduce water consumption and wastewater generation, this study attempted to perform enzymatic hydrolysis and fermentation of NaOH-treated SCB without washing process. It showed that after pretreatment and solid-liquid separation, NaOH-treated SCB could be directly hydrolysed by cellulase via pH and solid-liquid adjustment without washing steps, and the maximum enzymatic hydrolysis efficiency could reach to 70.2%. A domesticated Saccharomyces cerevisiae Y2034 which can endure 6-times diluted BL was obtained, and realized 67.5% ethanol yield from the enzymatic hydrolysate of unwashed NaOH-treated SCB. It provided a clue for converting NaOH-treated lignocellulose to ethanol at low water consumption and wastewater generation.


Assuntos
Celulose/química , Etanol/química , Saccharum/química , Hidróxido de Sódio/química , Celulose/metabolismo , Temperatura Baixa , Etanol/metabolismo , Fermentação , Hidrólise , Lignina/química , Lignina/metabolismo , Saccharomyces cerevisiae/metabolismo , Saccharum/metabolismo , Águas Residuárias/química
8.
Chem Commun (Camb) ; 55(68): 10158-10161, 2019 Sep 04.
Artigo em Inglês | MEDLINE | ID: mdl-31389420

RESUMO

We developed a chemical method to covalently functionalize cellulose nanofibers and cellulose paper with mannoside ligands displaying a strong affinity for the FimH adhesin from pathogenic E. coli strains. Mannose-grafted cellulose proved efficient to selectively bind FimH lectin and discriminate pathogenic E. coli strains from non-pathogenic ones. These modified papers are valuable tools for diagnosing infections promoted by E. coli, such as cystitis or inflammatory bowel diseases, and the concept may be applicable to other life-threatening pathogens.


Assuntos
Celulose/química , Escherichia coli K12/isolamento & purificação , Mananas/química , Nanofibras/química , Adesinas de Escherichia coli/metabolismo , Aderência Bacteriana/efeitos dos fármacos , Técnicas de Tipagem Bacteriana/instrumentação , Técnicas de Tipagem Bacteriana/métodos , Linhagem Celular Tumoral , Celulose/metabolismo , Escherichia coli K12/química , Fezes/microbiologia , Proteínas de Fímbrias/metabolismo , Microbioma Gastrointestinal/efeitos dos fármacos , Humanos , Mananas/metabolismo , Papel , Ligação Proteica
9.
J Agric Food Chem ; 67(35): 9840-9850, 2019 Sep 04.
Artigo em Inglês | MEDLINE | ID: mdl-31424924

RESUMO

In the present study, methanolysis of poplar biomass was conducted for the selective transformation of hemicellulose and lignin, which leads to methyl glycosides (mainly C5 glycosides) and lignin fragments in the liquefied products that can be separated according to their difference in hydrophilicity. The distribution of methyl glycosides and delignification was dependent on the presence of acid catalysts and reaction temperatures. The obtained lignin fraction was separated into solid lignin fragments and liquid lignin oil according to their molecular weight distribution. Subsequently, directional conversion of methyl C5 glycosides into methyl levulinate was performed with dimethoxymethane/methanol as the cosolvent. A yield of 12-30% of methyl levulinate yield (based on the methyl glycoside) was achieved under these conditions. The remaining cellulose-rich substrate showed enhanced susceptibility to enzymatic hydrolysis, resulting in a yield of glucose of above 70%. Overall, the described strategy shows practical implications for the effective valorization of biomass.


Assuntos
Fracionamento Químico/métodos , Glucose/isolamento & purificação , Ácidos Levulínicos/isolamento & purificação , Metanol/química , Fenóis/isolamento & purificação , Extratos Vegetais/isolamento & purificação , Populus/química , Madeira/química , Catálise , Celulose/química , Celulose/isolamento & purificação , Glucose/química , Ácidos Levulínicos/química , Lignina/química , Lignina/isolamento & purificação , Fenóis/química , Extratos Vegetais/química
10.
Food Chem ; 300: 125194, 2019 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-31325749

RESUMO

The effects of near freezing temperature (NFT) storage at -1.9 °C on cell wall degradation of 'Shushanggan' apricot was studied comparing to 0 °C and 5 °C storage. Our results indicated that NFT storage strongly inhibited the solubilization of Na2CO3-soluble pectin and cellulose, by the suppression of cell wall modifying enzymes (polygalacturonase, ß-Galactosidase, pectin methyl esterase and cellulase) and related genes expressions. The loss of side chains was the main modification in CDTA (Cyclohexane-diamine-tetraacetic Acid)-soluble pectin during storage and made the main contribution to the softening of apricot, while the loss of side chain was suppressed by NFT storage. Microscopic observation showed that NFT storage delayed the degradation of pectin fraction and protected cell wall structure from loosing. This study proves that NFT storage is an effective technology to suppress the cell wall polysaccharides degradation and ultrastructure modification of apricot.


Assuntos
Parede Celular/ultraestrutura , Armazenamento de Alimentos/métodos , Polissacarídeos/química , Prunus armeniaca/química , Hidrolases de Éster Carboxílico/química , Hidrolases de Éster Carboxílico/metabolismo , Parede Celular/química , Parede Celular/metabolismo , Celulose/química , Temperatura Baixa , Congelamento , Frutas/química , Frutas/citologia , Frutas/ultraestrutura , Pectinas/química , Células Vegetais/química , Células Vegetais/ultraestrutura , Poligalacturonase/química , Poligalacturonase/metabolismo , Polissacarídeos/metabolismo , Prunus armeniaca/citologia , Solubilidade , beta-Galactosidase/química , beta-Galactosidase/metabolismo
11.
Food Chem ; 298: 125041, 2019 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-31261000

RESUMO

Edible packaging films play an important role in extending the shelf life of food products. In this work, the properties of cellulose nanofiber (CNF) reinforced hemicelluloses/chitosan-based edible films with xylooligosaccharides (XOS) have been evaluated. Results showed that the tensile strength (TS) of the film can be increased by 2.5 times with adding 5 wt% CNF. Incorporating 1.79-7.18% XOS into hemicelluloses-chitosan matrix only caused slightly higher water vapor permeability, and the composite films exhibited good hydrophobicity, thermal stability, and high transparency. The hemicelluloses/chitosan films with 1.79-5.38% XOS had higher TS (42.7-50.7 MPa) and lower oxygen permeability (OP, 4.95-5.06 cm3 µm/m2·day·kPa) than those containing 7.18% XOS. Additionally, ∼92.6% XOS in films can be released in simulated gastric fluid within 60 min. Overall, XOS (1.79-5.38%) with prebiotic properties can be added to films successfully to improve the functionality and the films were fit for food-packaging where high TS and low OP are required.


Assuntos
Celulose/química , Quitosana/química , Glucuronatos/química , Nanofibras/química , Oligossacarídeos/química , Embalagem de Alimentos/métodos , Suco Gástrico , Humanos , Microscopia Eletrônica de Varredura , Permeabilidade , Polissacarídeos/química , Solubilidade , Espectroscopia de Infravermelho com Transformada de Fourier , Vapor , Resistência à Tração , Difração de Raios X
12.
Bioresour Technol ; 289: 121755, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31301946

RESUMO

A novel approach was proposed for the production of xylooligosaccharides by direct pre-hydrolysis using gluconic acid as catalyst. Maximum xylooligosaccharides (degree of polymerization 2-6) yield of 53.2% could be obtained in 60 min through 5% gluconic acid hydrolysis of sugarcane bagasse at 150 °C. Furthermore, the yield of glucose from solids following gluconic acid hydrolysis treatment was 86.2% after fed-batch enzymatic hydrolysis with 10% solids loading. Results indicated that gluconic acid pretreatment combined with enzymatic hydrolysis could be successfully applied to sugarcane bagasse substrate. Subsequently, glucose could be efficiently bio-oxidized to gluconic acid by Gluconobacter oxydans ATCC 621H with 93.1% yield, and sugarcane bagasse derived gluconic acid has been proved to be an effective catalyst for xylooligosaccharides production. In this study, xylooligosaccharides production from sugarcane bagasse by gluconic acid hydrolysis demonstrated a great potential with respect to the production of these probiotics around the world.


Assuntos
Celulose/química , Gluconatos/metabolismo , Glucuronatos/metabolismo , Oligossacarídeos/metabolismo , Saccharum/química , Biocatálise , Glucose/metabolismo , Hidrólise
13.
Pharm Res ; 36(10): 139, 2019 Jul 29.
Artigo em Inglês | MEDLINE | ID: mdl-31359156

RESUMO

PURPOSE: To identify the minimum interfacial bonding strength (IBS) required for bilayer tablets to sustain the stresses experienced during manufacturing, transportation, and handling. METHODS: Bilayer tablets of a number of formulations with systematically varied IBS were prepared on a materials testing macine. Five bilayer tablets with the same IBS were repeatedly dropped at a fixed height in a friabilator and integrity of the interface was periodically examined. The number of tablets free from observable defects at the interface was plotted as a function of the number of drops. The IBS for all five tablets to remain intact after 1000 drops was taken as the minimum IBS for a given formulation. RESULTS: The minimum IBS depends on both layer composition and tablet size. For bilayer tablets made with more brittle materials or a larger size, a higher minimum IBS is required to pass the survival test. The incorporation of HPMC leads to a lower minimum IBS. An IBS of 0.26 MPa is sufficient for all bilayer tablet formulations and sizes to pass the survival test in this work. CONCLUSIONS: A minimum IBS of 0.26 MPa is recommended as a tentative criterion for bilayer tablets of most materials to avoid quality issues arising from inadequate IBS.


Assuntos
Excipientes/química , Comprimidos/química , Celulose/química , Composição de Medicamentos/métodos , Estabilidade de Medicamentos , Lactose/química , Tamanho da Partícula , Estresse Mecânico , Propriedades de Superfície , Resistência à Tração
14.
Mar Pollut Bull ; 142: 394-407, 2019 May.
Artigo em Inglês | MEDLINE | ID: mdl-31232317

RESUMO

The effect of fiber type (cotton, polyester, and rayon), temperature, and use of detergent on the number of microfibers released during laundering of knitted fabrics were studied during accelerated laboratory washing (Launder-Ometer) and home laundering experiments. Polyester and cellulose-based fabrics all shed significant amounts of microfibers and shedding levels were increased with higher water temperature and detergent use. Cellulose-based fabrics released more microfibers (0.2-4 mg/g fabric) during accelerated laundering than polyester (0.1-1 mg/g fabric). Using well-controlled aquatic biodegradation experiments it was shown that cotton and rayon microfibers are expected to degrade in natural aquatic aerobic environments whereas polyester microfibers are expected to persist in the environment for long periods of time.


Assuntos
Celulose/metabolismo , Lavanderia , Poliésteres/metabolismo , Têxteis , Poluentes Químicos da Água/metabolismo , Biodegradação Ambiental , Celulose/química , Fibra de Algodão , Poliésteres/química , Água/química , Poluentes Químicos da Água/química
15.
Int J Food Microbiol ; 305: 108246, 2019 Sep 16.
Artigo em Inglês | MEDLINE | ID: mdl-31238193

RESUMO

Cellulosic pads, amended with emulsions containing essential oils of thyme and oregano, exhibited antimicrobial activity against the psychrophilic microbiota of minced beef. In addition, the pads were active against specific meat bacterial species (Pseudomonas putida, Pseudomonas fragi, Pseudomonas fluorescens, Enterococcus faecalis and Lactococcus lactis) and some common foodborne pathogens (Salmonella enterica, Campylobacter jejuni and Staphylococcus aureus). Three emulsions, IT131017, Mediterranean and Etnic, containing different percentages of carvacrol, thymol, linalool, and ɑ and ß-pinene, significantly reduced the growth of S. enterica and P. putida. Pads derived from emulsions Mediterranean and Etnic induced slight (0.3-0.8 Log10 CFUs/g) but reproducible reduction of the psychrophilic microbiota in minced meat and hamburger stored for 12 and 15 days at 4 °C.


Assuntos
Antibacterianos/farmacologia , Cinnamomum zeylanicum/química , Óleos Voláteis/farmacologia , Origanum/química , Extratos Vegetais/farmacologia , Carne Vermelha/microbiologia , Thymus (Planta)/química , Animais , Antibacterianos/química , Bactérias/efeitos dos fármacos , Bactérias/crescimento & desenvolvimento , Compostos Bicíclicos com Pontes , Bovinos , Celulose/química , Emulsões/química , Emulsões/farmacologia , Microbiologia de Alimentos , Carne/microbiologia , Monoterpenos/química , Monoterpenos/farmacologia , Óleos Voláteis/química , Extratos Vegetais/química , Carne Vermelha/análise , Timol/química , Timol/farmacologia
16.
Environ Sci Pollut Res Int ; 26(24): 24516-24531, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31230249

RESUMO

Ammoniacal nitrogen is considered as one of the major pollutants of the leachate generated from the landfill site and has the potential to deteriorate the environment as well as health. Considering this, locally available agricultural waste, i.e., sugarcane bagasse ash, was employed as an adsorbent for the removal of ammoniacal nitrogen from landfill leachate. Batch-mode experiments were conducted to see the effect of dose (2-60 g L-1), pH (2-12), and temperature (20-60 °C) on ammoniacal nitrogen adsorption. Application of sugarcane bagasse ash showed 60% removal of ammoniacal nitrogen (50 mg L-1 strength) at an optimum dose of 20 g L-1 and 180 min of contact time with an adsorption capacity of 0.31 mg g-1. The Langmuir adsorption model was found to be best fit at 40 °C with R2 = 0.944, depicting a monolayer coverage of ammoniacal nitrogen onto sugarcane bagasse ash. According to the result, solute uptake rate could be well described by the pseudo-second-order model (R2 = 0.928), whereas the intraparticle diffusion model and Boyd plot indicated that the overall adsorption rate is governed by the external mass transfer. Thermodynamic studies revealed that adsorption is feasible, spontaneous, and endothermic in nature. Hence, the study shows that sugarcane bagasse ash could turn out to be a cost-effective adsorbent for the removal of ammoniacal nitrogen from leachate.


Assuntos
Celulose/química , Nitrogênio/análise , Poluentes Químicos da Água/análise , Adsorção , Concentração de Íons de Hidrogênio , Cinética , Nitrogênio/química , Saccharum , Temperatura Ambiente , Poluentes Químicos da Água/química
17.
Carbohydr Polym ; 220: 110-117, 2019 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-31196528

RESUMO

High quality cellulose nanoparticles (CNP) were isolated from water hyacinth stem cellulose (Cel-WH) extracted via successive thermochemical and alkaline-peroxide treatments, and further enzymatically hydrolysed using the commercial cellulase complex, NS22086, at 50ºC. The maximum CNP concentration was reached after 120 min of enzymatic hydrolysis, with a hydrodynamic diameter in the order of 200-250 nm and an increase of 5% in crystallinity as compared with Cel-WH. The obtained rod-shaped cellulose nanocrystals, as revealed by atomic force microscopy (AFM), exhibited a nominal diameter of 15.6-29.4 nm, a length of 56-184.8 nm, and a height of 2.85-6.43 nm, indicating a low tendency to form aggregates. In the present study, it was found that water hyacinth stems are a valuable source for the isolation of high-quality CNP using an environmentally friendly procedure, with potential applications in nanomedicine and nanopharmacology.


Assuntos
Celulose/química , Eichhornia/química , Nanopartículas/química , Caules de Planta/química , Celulase/química , Hidrólise , Microscopia de Força Atômica/métodos , Nanomedicina/instrumentação , Difração de Raios X/métodos
18.
Carbohydr Polym ; 220: 228-235, 2019 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-31196545

RESUMO

With the increasing requirement of environmental protection, the development of lubricating materials with non-toxicity and good biodegradability becomes more and more significant. As the novel green nanomaterial derived from natural cellulose, cellulose nanocrystals (CNCs) in the present work were prepared from native cotton and added into polyalphaolefin (PAO) base oil as the lubricant additive. To improve the compatibility of CNCs with PAO, the surface of CNCs were grafted by stearoyl chains, which entangled with polyolefin chains and led to a good dispersibility and stability of the colloidal solution. This hybrid oil with the elevated viscosity improved the formation of lubricant film in the boundary lubrication regime. Combining with the mending effect of CNC particles on the surface roughness and scars, both the friction and the wear were dramatically reduced. Specifically, the introduction of 2 wt% modified nanocrystals (mCNC) in PAO base oil reduced the coefficient of friction (COF) by 30%. The results of this study suggest that cellulose nanocrystal is a promising ecofriendly and effective lubricant additive.


Assuntos
Alcenos/química , Celulose/química , Gossypium/metabolismo , Lubrificantes/química , Nanopartículas/química , Fricção , Lubrificação , Propriedades de Superfície , Viscosidade
19.
Carbohydr Polym ; 219: 12-20, 2019 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-31151508

RESUMO

Including additives in the culture media during bacterial cellulose (BC) biosynthesis is a traditional method to produce BC-based nanocomposites. This study examines a novel fermentation process, which is to co-culture Gluconacetobacter hansenii (G. hansenii) with Escherichia coli (E. coli) under static conditions, to produce BC pellicles with enhanced mechanical properties. The mannose-rich exopolysaccharides (EPS) synthesized by E. coli were incorporated into the BC network and affected the aggregation of co-crystallized microfibrils without significantly changing the crystal sizes of BC. When co-culturing G. hansenii ATCC 23769 with E. coli ATCC 700728, which produced a low concentration of EPS at 3.3 ± 0.7 mg/L, the BC pellicles exhibited a Young's modulus of 4,874 ± 1144 MPa and a stress at break of 80.7 ± 21.1 MPa, which are 81.9% and 79.3% higher than those of pure BC, respectively. The growth dynamics of the two co-cultured strains suggested that the production of BC and EPS were enhanced through co-culturing fermentation.


Assuntos
Celulose/química , Técnicas de Cocultura/métodos , Escherichia coli/metabolismo , Gluconacetobacter/metabolismo , Nanocompostos/química , Metabolismo dos Carboidratos , Cristalização , Fermentação , Fenômenos Mecânicos , Microfibrilas
20.
Carbohydr Polym ; 219: 210-218, 2019 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-31151519

RESUMO

Scaffold plays a critical role in stem cell differentiation and tissue regeneration. Composite scaffolds composed of bacterial cellulose (BC) and collagen (Col) in different ratios (1:1, 3:1, 5:1) were fabricated in this study. The composite scaffolds exhibit a well-organized interconnected porous structure, significantly better physical stability than Col scaffold, and more water uptake up to 400%. They were also favorable with cell attachment and growth. After osteogenic induction of umbilical cord blood derived mesenchymal stem cells (UCB-MSCs) for 3 weeks, we found more up-regulated osteogenic markers (collagen type 1, osteocalcin, bone sialoprotein) and significantly elevated proteins and calcium deposition, particularly with BC/Col (5:1) scaffold. When PKH-26 pre-labelled MSC-loaded scaffolds were subcutaneously transplanted in a mouse model, they showed many PKH-26-labelled cells and positive signals of α-smooth muscle actin, for neovascularization in the BC/Col (5:1). The current work demonstrates that our BC/Col composites may be promising as a bone tissue-engineered scaffold.


Assuntos
Celulose/química , Colágeno/química , Gluconacetobacter xylinus/metabolismo , Engenharia Tecidual/métodos , Tecidos Suporte/química , Animais , Regeneração Óssea/efeitos dos fármacos , Diferenciação Celular/efeitos dos fármacos , Celulose/uso terapêutico , Colágeno/uso terapêutico , Humanos , Células-Tronco Mesenquimais/efeitos dos fármacos , Camundongos , Células NIH 3T3 , Osteogênese/efeitos dos fármacos
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