Synthesis of amino-functionalized nanocellulose by guanidine based deep eutectic solvent and its application in fine fibers retention.

A guanidine-based Deep Eutectic Solvent (DES) consisting of 1,3-diaminoguanidine monohydrochloride and glycerol was utilized to prepare C-CNC from dissolving pulp. The pulp fibers were oxidized to dialdehyde cellulose by periodate, then fibrillated through the hydrogen bonds shear of DES and aminocationized through Schiff base effect of the amino groups in the DES solvent to obtain C-CNC. The results revealed that the characterization of the DES (such as viscosity, polarity, and pH) was related to the molar ratio of glycerol/guanidine-salts. The hydrogen bond network structure of DES solvent with optimal system was simulated by DFT and its damage to fiber hydrogen bond network was predicted. The C-CNC produced under the optimal reaction conditions (molar ratio of 1:2, 90 °C for 2 h) was highly dispersible with an average length and diameter of 85 ± 35 nm and 5.0 ± 1.2 nm, a charge density of 2.916 mol/g. C-CNC exhibited excellent flocculation when added to fine fiber suspensions of chemomechanical slurries, achieving rapid flocculation and settling onto fibers in <1 min. The DES solvent maintained its reactivity after 5 cycles. This study lays the foundation for the batch preparation of nanocellulose in an environmentally friendly manner and its application as a green additive in paper industry.

Preparation and characterization of cellulose nanofibril/chitosan aerogels with high-adsorbability and sensitive indication for indoor free formaldehyde.

The toxic volatile organic compounds (VOCs), especially formaldehyde (FA), released from decoration materials pose a great threat to human health. In this study, formaldehyde adsorption performance of the specially formulated nanocellulose/chitosan aerogel (CNFCA) was investigated in simulated atmosphere. The physicochemical property of the composite aerogel was characterized, which had a large specific surface area (153.67 m2/g), a rough surface and an ultra-thin and porous structure. The composite aerogel showed excellent adsorption capacity for the formaldehyde, its theoretical maximum adsorption capacity was as high as 83.89 mg/g, and the adsorption process was more in accordance with the pseudo-second-order kinetics. The chromogenic reaction between the 4-amino-3-benzo-5-mercapto-1,2,4-triazolium (AHMT) and CNFCA was found that the color of the composite aerogel was depended on the free formaldehyde concentration. Based on this phenomenon, a colorimetric card was proposed and built to detection the formaldehyde in the atmosphere. Moreover, the adsorption mechanism research was found that the CNFCA with a multilayer structure belonged to physicochemical complex adsorption.

Selective degradation of hemicellulose and lignin for improving enzymolysis efficiency via pretreatment using deep eutectic solvents.

Deep eutectic solvents (DESs) with different acidity and alkalinity were applied for biomass pretreatment, and the conditions were optimized by response surface methodology. The results showed that lactic acid/betaine hydrochloride had the optimal pretreatment efficiency, where the removal rates of hemicellulose and lignin came up to 89% and 73%, and the enzymolysis efficiency was as high as 92%. Furthermore, eight types of chloride salts with different valence states were introduced into the DESs as the third component. The chloride salts could improve the pretreatment efficiency and positively correlated with the metal valence state. Specifically, AlCl3 was significantly superior in improving the pretreatment efficiency, where the enzymolysis efficiency reached 96% due to the destruction of crystalline region and the esterification of partial cellulose. Therefore, it is proposed that adding highly valent metal salts to acidic DESs has higher pretreatment and enzymatic efficiency.

Facile preparation of cellulose nanofibrils (CNFs) with a high yield and excellent dispersibility via succinic acid hydrolysis and NaClO2 oxidation.

An efficient and low-cost approach to preparing CNFs with succinic acid hydrolysis and NaClO2 oxidation is explored. High-temperature-short-time hydrolysis can depolymerize the cellulose, whereas the dispersibility of the CNFs is hugely enhanced by NaClO2 oxidation under alkaline condition. The degradation of cellulose in succinic acid hydrolysis follows first-order reaction kinetics and is severely influenced by the hydrolysis temperature, moreover, the molecular chains of the cellulose are seriously cracked under the optimized condition. The NaClO2 oxidation greatly improves the zeta potential (-36.2 mV) and the dispersibility of the CNFs. The obtained CNFs have an ultimate yield of 94.6%, and the diameter distribution is mainly within 20-40 nm. In addition, some amount of carboxyl groups in the cellulose will be instead of the hydroxyl groups, and the crystallinity of the CNFs is significantly increased.

The structural features of hemicelluloses dissolved out at different cooking stages of active oxygen cooking process.

This work described the morphologic changes of corn stalk and the structural characterization of its hemicelluloses dissolved in yellow liquor at different cooking stages. The results showed that active oxygen cooking process was an efficient method to depolymerize the corn stalk into cellulose, hemicelluloses, and lignin as a pretreatment of biomass conversion. This cooking process can also be divided into three phases: bulk delignification, extended delignification, and residual delignification. During the heating-up period 57.67% of hemicelluloses and 62.31% of lignin were removed from the raw material. However, only 15% of hemicelluloses and 23.21% of lignin were removed during at temperature' period. The hemicelluloses from the corn stalk and yellow liquor were composed of (1→4)-ß-D-xylopyranose backbones substituted with α-l-arabinofuranosyl, 4-O-methyl-α-D-glucuronic acid, and some methoxyl residues. The backbones of hemicelluloses were gradually cleaved during the cooking process. The acetyl groups substituted with xylopyranosyl residues were completely cleaved during the cooking process.

Enhancement of eucalypt chips' enzymolysis efficiency by a combination method of alkali impregnation and refining pretreatment.

A combination process of alkali impregnation and refining was used as a pretreatment to improve the production of fermentable sugar. The surface structures and crystallinities of wood samples were characterized to explain the relationships between the pretreatment action and enzymatic efficiency. After refining, the reducing sugar contents in hydrolyzates were analyzed by UV-Vis and HPLC. The results showed that the enzymatic efficiency could be improved by the combined pretreatment, due to the increment of specific surface area and the release of more free hydroxyls. Comparing to the sodium hydroxide and deionized water, the impregnation with magnesium hydroxide had low refining energy consumption and high yield of reducing sugar (glucose and xylose) in enzymolysis process, where about 560 kWh/t of the energy was saved in refining, and the yield of the reducing sugar was as high as 91.53%. And the enzymolysis could be improved by a certain amount of magnesium ions.

Efficient enzymatic hydrolysis of the bagasse pulp prepared with active oxygen and MgO-based solid alkali.

The enzymatic hydrolysis of the bagasse pulp prepared from the treatment process with active oxygen and MgO-based solid alkali was studied. The hydrolysates were tested by IC (ionic chromatography) for the analysis of monosaccharide. Additionally, the changes of pulp before and after hydrolysis were characterized with Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray diffraction (XRD), Kajaani cellulose automatic analyzer and atomic force microscopy (AFM) techniques. The results showed that an optimized sugar yield of 82.38% was obtained at the substrate concentration of 5% for 72h with the enzyme dosage of 15IU/g. Furthermore, as the length of the cellulose fiber decreased, the crystallinity of cellulose increased, and more depressions appeared on the surface of pulp after enzymatic hydrolysis.

Characterization of changes of lignin structure in the processes of cooking with solid alkali and different active oxygen.

The cooking with solid alkali and active oxygen has a high selectivity for delignification. In the present work, the O(2) and H(2)O(2) were separately combined with MgO used in cornstalk cooking for investigating their effects on delignification. After cooking, the lignins in raw material, pulp, and yellow liquor were all characterized by HSQC NMR. The results showed that the syringyl (S/S'/S″) units and ß-O-4' (A/A'/A″) structures had different reactivity in the cooking with MgO and H(2)O(2) due to their different structures on side-chains. Whereas the syringyl (S/S'/S″) units could be completely decomposed when the MgO and O(2) were used, and the ß-O-4' (A/A'/A″) structures could be partly degraded. A novel structure G' unit with a carbonyl group was only generated in the cooking with MgO and O(2). In addition, the H unit, non-phenolic ß-ß' (B) and ß-5' (C) structures were all stable in both of the two cooking processes.

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.

Structural characterization of lignin in the process of cooking of cornstalk with solid alkali and active oxygen.

A novel, efficient, and environmentally friendly technology is used in cornstalk cooking, active oxygen (O2 and H2O2) cooking with solid alkali (MgO). After the cooking, the milled wood lignin in the raw material and pulp and the water-soluble and insoluble lignin in the yellow liquor were all characterized by attenuated total reflectance Fourier transform infrared spectroscopy and two-dimensional heteronuclear single-quantum coherence NMR. The results showed that the cooking procedure with solid alkali and active oxygen had a high selectivity for delignification, which could remove 85.5% of the lignin from the raw material. The syringyl (S/S'/S') units could be dissolved preferentially because of their high reactivity, and a novel guaiacyl unit with a carbonyl group (G') was generated in the cooking process. Moreover, during the cooking, the ß-O-4' (A/A'/A″) structures as the main side-chain linkages in all the lignins could be partly broken and the ß-O-4' (A') with a ring-conjugated structure was readily attacked by oxygen, whereas the H unit and ß-5' and ß-ß' structures were found to stay stable without characteristic reaction.

Correlation between hammerhead ribozyme-mediated eggshell protein gene cleavage and reproduction inhibition of Schistosoma japonicum.

Schistosoma japonicum (S. japonicum) is an extremely harmful pathogen, which infects humans and causes severe public health problems. To date, no effective therapeutic drugs for this pathogen are available. In this study, we designed and constructed three hammerhead ribozymes targeting the eggshell protein gene of S. japonicum (SjESG). The cleavage activities of these three ribozymes were determined using cleavage experiments. The in vitro cleavage results showed that among the three synthesized ribozymes (Rz1, Rz2 and Rz3), Rz1 and Rz3 cleaved their target RNAs effectively. However, Rz2 did not cleave its target RNA detectably. The putative therapeutic roles of these three ribozymes to inhibit the reproduction of S. japonicum in mice were studied in vivo. Compared with the negative controls, Rz1 and Rz3 treatments resulted in increased levels of IFN-γ but decreased levels of IL-4 in mice. Rz2 affected levels of IFN-γ and IL-4 to degrees similar with those caused by the vector controls. In addition, Rz1 and Rz3 reduced the amounts of adult worms and eggs in the livers of mice more extensively than Rz2 and the vector controls. Altogether, these results suggest a correlation between the in vitro cleavage abilities of Rz1 and Rz3 and their roles in reproduction inhibition of S. japonicum.

Changes of the surface structure of corn stalk in the cooking process with active oxygen and MgO-based solid alkali as a pretreatment of its biomass conversion.

This study presents a novel, efficient and environmentally friendly process for the cooking of corn stalk that uses active oxygen (O2 and H2O2) and a recoverable solid alkali (MgO). The structural changes on the surface of corn stalk before and after cooking were characterized by attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) techniques. The results showed that lignin and extractives were effectively removed, especially those on the surface of corn stalk. Additionally, the changes included becoming fibrillar, the exposure of cellulose and hemi-cellulose and the pitting corrosion on the surface, etc. The results also showed that the removal reaction is from outside to inside, but the main reaction is possibly on the surface. Furthermore, the results of active oxygen cooking with a solid alkali are compared with those of alkaline cooking in the paper.

[Rapid detection of norwalk GII with reverse transcription loop-mediated isothermal amplification].

To develop a reverse transcription-loop-mediated isothermal amplification (RT-LAMP) assay for rapid and sensitive detection of Norwalk GII. 4 primers which recognized 6 distinct regions on the RNA-dependent RNA polymerase gene of Norwalk GII were designed and used for LAMP assay. Norwalk GII RNA was amplified under isothermal conditions (65 degrees C) for 120 min, and LAMP results were then judged with naked eye, SYBR Green I staining, electrophoretic analysis and restriction digestion. To evaluate the specificity of the RT-LAMP, 48 fecal specimens of Norwalk GII and 12 fecal specimens of group A rotaviruses were tested. To compare the sensitivity of the RT-LAMP with that of conventional RT-PCR, Norwalk GII RNA was serially diluted and amplified by RT-LAMP and RT-PCR, respectively. With 46 fecal specimens of Norwalk GII, observation with naked eyes, SYBR Green I staining and electrophoretic analysis were able to detect the PCR products in the RT-LAMP assay. The specificity of RT-LAMP products was also confirmed by digestion of the RT-LAMP products with restriction enzymes. No RNA amplification was observed in 2 fecal specimens of Norwalk GII and 12 fecal specimens of group A rotaviruses. The specificity of the RT-LAMP assay with regard to RT-PCR were 100% for Norwalk GII. The detection limits of RT-LAMP was 15.6 pg/tube for Norwalk GII and similar to that of a RT-PCR assay. Compared to RT-PCR, the RT-LAMP assay has been proven to be a rapid, sensitive, specific and accurate method for detection of the Norwalk GII in fecal specimens, and that RT-LAMP assay is potentially useful for the rapid detection of Norwalk GII from fecal specimens in outbreaks of infectious diarrhea.

[Detection of Toxoplasma gondii DNA by loop-mediated isothermal amplification].

OBJECTIVE: To detect Toxoplasma gondii DNA by loop-mediated isothermal amplification (LAMP). METHODS: DNA was extracted by phenol-chloroform extraction from T. gondii tachyzoites. Four primers which recognized 6 distinct regions on the B1 gene of T. gondii were designed and used for LAMP assay. To evaluate the specificity of the method, Plasmodium vivax, P. falciparum, Pneumocystis carinii, Schistosoma japonicum, and mouse leucocytes were used gs controls. The parasite extract (T. gondii) was 10-fold serially diluted for evaluating the sensitivity of LAMP, and was amplified by LAMP. LAMP results were read with naked eye and analyzed by electrophoresis. RESULTS: After LAMP reaction, positive amplification was observed with T. gondii, but no positive signal was noted for the negative controls in the study. The sensitivity of LAMP assay reached up to 2-3 T. gondii tachyzoites/ml per reaction. CONCLUSION: LAMP assay shows proper specificity and sensitivity for the detection of T. gondii.

[Induction of protective immunity against Schistosoma japonicum by pcDNA3.1/Sj20.8 nucleic acid vaccine in BALB/c mice].

Sj20.8 gene was amplified by PCR and inserted into eukaryotic expression plasmid pcDNA3.1 to construct recombinant plasmid pcDNA3.1/Sj20.8, which was then injected into the quadriceps femoris of the BALB/c mice. Results showed that the Sj20.8 antigen was low expressed in the local tissue of the mice, and was not able to significantly reduce eggs in the liver than in the control mice.

[Construction of Sjcb2 DNA vaccine and its expression in HeLa cells].

A recombinant plasmid containing cathepsin B endopeptidase of Schistosoma japonicum (Sjcb2) was constructed, indentified by PCR, restrictive enzyme, digestion and DNA sequencing, and expressed into mammalian cells. Immunochemistry examination showed that the Sjcb2 gene can be expressed in the eukaryotic system, providing a basis for the development of schistosome DNA vaccine.

[Acquisition and analysis of 149 ESTs and 18 novel genes of Schistosoma japonicum].

OBJECTIVE: To acquire and analyze adult stage Schistosoma japonicum (Chinese strain) expressed sequence tags and new genes from an adult S. japonicum cDNA library, and to search new vaccine candidates and drug targets. METHODS: A cDNA library was constructed from adult stage S. japonicum. Clones were selected randomly from the cDNA library and were sequenced. ESTs and new genes were acquired after analysis in GenBank databases by BLAST and other programs. All ESTs and new genes were submitted to GenBank and received accession numbers. RESULTS: 149 ESTs were acquired from a total 382 clones that were randomly selected from the adult S. japonicum cDNA library. All ESTs were successfully submitted to the dbEST at Genbank. Some of them were homologous with sequences of male, female, egg, schistosomula, cercaria and miracidia of S. japonicum. 18 new genes of adult S. japonicum were acquired. Some genes were housekeeping genes and some genes might be interesting as vaccine candidates or drugs targets. CONCLUSIONS: The EST strategy is a rapid, efficient and economical method to acquire ESTs and to discover new genes of adult stage S. japonicum from cDNA libraries.