Efficient dissolution of cellulose in slow-cooling alkaline systems and interacting modes between alkali and urea at the molecular level.

The dissolution of microcrystalline cellulose (MCC) in a urea-NaOH system is beneficial for its mechanical processing. The apparent MCC solubility was greatly improved to 14 wt% under a slow-cooling condition with a cooling rate of -0.3 °C/min. The cooling curve or thermal history played a crucial role in the dissolution process. An exotherm (-54.7 ± 3 J/g MCC) was detected by DSC only under the slow-cooling condition, and the cryogenic dissolution of MCC was attributed to the exothermic interaction between MCC and solvent. More importantly, the low cooling rate promoted the dissolution of MCC by providing enough time for the diffusion of OH- and urea into MCC granules at higher temperatures. The Raman spectral data showed that the intramolecularly and intermolecularly hydrogen bonds in cellulose were cleaved by NaOH and urea, respectively. XPS and solid-state 13C NMR results showed that hydrogen bonds were generated after dissolution, and a dual-hydrogen-bond binding mode between urea and cellulose was confirmed by DFT calculations. Both the decrease of enthalpy and increase of entropy dominated the spontaneity of MCC dissolution, and that is the reason for the indispensability of cryogenic environment. The high apparent solubility of MCC in the slow-cooling process and the dissolution mechanism are beneficial for the studies on cellulose modification and mechanical processing.

Fumigaclavine C ameliorates liver steatosis by attenuating hepatic de novo lipogenesis via modulation of the RhoA/ROCK signaling pathway.

BACKGROUND: Non-alcoholic fatty liver disease (NAFLD) has been well defined as a common chronic liver metabolism disorder. Statins as a first-line therapeutic treatment had some side effects. Here, we found that Fumigaclavine C (FC) was collected from endophytic Aspergillus terreus via the root of Rhizophora stylosa (Rhizophoraceae), had potential anti-adipogenic and hepatoprotective effects both in vitro and in vivo without obvious adverse side effects. However, the mechanisms of the prevention and management of FC for hepatic steatosis are incompletely delineated. METHODS: The pharmacodynamic effects of FC were measured in high-fat diet (HFD)-induced obese mice. Liver index and blood biochemical were examined. Histopathological examination in the liver was performed by hematoxylin & eosin or oil red O. The levels of serum TG, TC, LDL-c, HDL-c, FFA, T-bili, ALT, AST, creatinine, and creatine kinase were estimated via diagnostic assay kits. The levels of hepatic lipid metabolism-related genes were detected via qRT-PCR. The expression levels of hepatic de novo lipogenesis were quantitated with Western blot analysis.  RESULTS: FC-treatment markedly reduced hepatic lipid accumulation in HFD-induced obese mice. FC significantly attenuated the hepatic lipid metabolism and ameliorated liver injury without obvious adverse side effects. Moreover, FC also could dose-dependently modulate the expressions of lipid metabolism-related transcription genes. Mechanically, FC notably suppressed sterol response element binding protein-1c mediated de novo lipogenesis via interfering with the RhoA/ROCK signaling pathway by decreasing the levels of geranylgeranyl diphosphate and farnesyl diphosphate. CONCLUSIONS: These findings suggested that FC could improve hepatic steatosis through inhibiting de novo lipogenesis via modulating the RhoA/ROCK signaling pathway.

Low-temperature aerobic carbonization and activation of cellulosic materials for Pb2+ removal in water source.

Targeting the removal of Pb2+ in wastewater, cellulosic materials were carbonized in an aerobic environment and activated via ion exchange. The maximum adsorption capacity reached 243.5 mg/g on an MCC-derived adsorbent activated with sodium acetate. The modified porous properties improved the adsorption capacity. The capacity could be completely recovered five times through elution with EDTA. Because of the negative effects of Ni, Mg, and Ca elements, the adsorption capacities of activated carbonized natural materials were lower than that of pure cellulose. N2 adsorption measurement showed that the adsorbent had a large specific surface area as well as abundant micropores and 4-nm-sized mesopores. FTIR and surface potential results proved that carboxyl group was generated in the aerobic carbonization, and was deprotonated during ion exchange. This adsorbent consisted of C-C bonds as the building blocks and hydrophilic groups on the surface. XPS results demonstrated that the Pb 4f binding energies were reduced by 0.7-0.8 eV due to the interaction between Pb2+ and the activated adsorbent, indicating that the carboxylate groups bonded with Pb2+ through coordination interactions. Pseudo-second-order and Elovich kinetic models were well fitted with the adsorption processes on the pristine and activated carbonized adsorbents, indicative of chemisorption on heterogeneous surfaces. The Freundlich expression agreed well with the data measured, and the pristine and activated adsorbents had weak and strong affinities for Pb2+, respectively. The Pb2+ adsorption process was exothermic and spontaneous, and heat release determined the spontaneity. The adsorption capacity is attributed to the carboxylate groups and pores generated in the aerobic oxidation and ion exchange procedures.

[Transformation mechanism of carbon tetrachloride and the associated micro-ecology in landfill cover, a typical functional layer zone].

Landfill is one of the important sources of carbon tetrachloride (CT) pollution, and it is important to understand the degradation mechanism of CT in landfill cover for better control. In this study, a simulated landfill cover system was set up, and the biotransformation mechanism of CT and the associated micro-ecology were investigated. The results showed that three stable functional zones along the depth, i.e., aerobic zone (0-15 cm), anoxic zone (15-45 cm) and anaerobic zone (> 45 cm), were generated because of long-term biological oxidation in landfill cover. There were significant differences in redox condition and microbial community structure in each zone, which provided microbial resources and favorable conditions for CT degradation. The results of biodegradation indicated that dechlorination of CT produced chloroform (CF), dichloromethane (DCM) and Cl- in anaerobic and anoxic zones. The highest concentration of dechlorination products occurred at 30 cm, which were degraded rapidly in aerobic zone. In addition, CT degradation rate was 13.2-103.6 µg/(m2·d), which decreased with the increase of landfill gas flux. The analysis of diversity sequencing revealed that Mesorhizobium, Thiobacillus and Intrasporangium were potential CT-degraders in aerobic, anaerobic and anoxic zone, respectively. Moreover, six species of dechlorination bacteria and eighteen species of methanotrophs were also responsible for anaerobic transformation of CT and aerobic degradation of CF and DCM, respectively. Interestingly, anaerobic dechlorination and aerobic transformation occurred simultaneously in the anoxic zone in landfill cover. Furthermore, analysis of degradation mechanism suggested that generation of stable anaerobic-anoxic-aerobic zone by regulation was very important for the harmless removal of full halogenated hydrocarbon in vadose zone, and the increase of anoxic zone scale enhanced their removal. These results provide theoretical guidance for the removal of chlorinated pollutants in landfills.

Heterotrophic nitrification and aerobic denitrification by a novel Acinetobacter sp. TAC-1 at low temperature and high ammonia nitrogen.

A novel strain was isolated from swinewastewater and identified as Acinetobacter sp. TAC-1 based on its phylogenetic and phenotypic characteristics. The strain TAC-1 was found to have a high ability to metabolize ammonium-N under low temperature condition. The strain TAC-1 could remove approximately 94.6% of ammonium-N (400 mg/L), 93.3% of nitrate-N (400 mg/L) and 42.4% of nitrite-N (400 mg/L) at 5 °C. The functional genes nitrate reductase gene (narG) and nitrite reductase gene (nirK, nirS) were successfully amplified by qPCR, further evidencing the heterotrophic nitrification and aerobic denitrification capability of Acinetobacter sp. TAC-1. The transcriptome data confirmed that the membrane transport protein and unsaturated fatty acid dehydrogenase-related genes of the strain TAC-1 were significantly up-regulated at 5 °C, enabling it to survive low temperatures. The high nitrogen removal ability at 5 °C makes this strain have a good application prospect.

Lead ion adsorption on functionalized sugarcane bagasse prepared by concerted oxidation and deprotonation.

Targeting the removal of Pb2+ in wastewater, sugarcane bagasse was treated with nitric acid and an alkaline solution to prepare adsorbents. On a typical adsorbent, the adsorption isotherms agreed well with the Langmuir expression, and the maximum adsorption capacity reached 200.3 mg/g. In the presence of 150 ppm Ca2+, a common cation in natural water, the Pb2+ adsorption capacity slightly declined. In contrast, Mg2+ obviously prohibited the adsorption for Pb2+. The spent adsorbent could be regenerated at least five times through elution with an EDTA solution. EDS and XPS results demonstrated that nitric acid functioned as an oxidant instead of nitrification agent in the treatment of bagasse. The adsorption process was consistent with quasi-second-order kinetics. Based on thermodynamic studies, the changes in enthalpy and Gibbs free energy were calculated to be - 33.3 and ca. - 18 kJ/mol, indicating that the adsorption process was exothermic and spontaneous. The equilibrium Pb2+ adsorption amounts were proportional to the numbers of carboxylate groups on different adsorbents. The binding energies of Pd 4f5/2 and Pd 4f7/2 XPS spectra of Pb2+ adsorbed were 0.6-0.7 eV lower than those of free Pb(NO3)2, indicating the transfer of electrons during adsorption. The conversion of hydroxymethyl groups in sugarcane bagasse into carboxylate groups, as well as the chelation between Pb2+ ions and carboxylate groups, was validated in this work, which is beneficial for the treatment of wastewater polluted by lead ions.

Fast and reversible adsorption for dibenzothiophene in fuel oils with metallic nano-copper supported on mesoporous silica.

Dibenzothiophene (DBT) in fuel oils causes the release of toxic sulfur oxide gases, and it is necessary to remove DBT in fuels. Herein, metallic copper was loaded on SBA-15 mesoporous silica through simple reduction reactions for the preparation of DBT adsorbents. On an adsorbent with a copper loading of 0.3 wt%, adsorption equilibrium was achieved within 5 min, and a DBT removal rate of 90.4% was achieved. The adsorption isotherm agreed with a linear Freundlich model and adsorption capacity was 12.1 mg sulfur/g. Nano-sized copper particles were observed by TEM, indicating the size effect of copper particles in DBT adsorption. A broad band, corresponding to copper-sulfur coordination bonds, was observed at 300-600 cm-1 in the Raman spectrum of DBT-doped adsorbent. Meanwhile, the band at 1233 cm-1 corresponding to C = C (-S) bonds in DBT was shifted to 1229 cm-1 in DBT adsorbed. XPS and Cu LMM XPS spectra proved that Cu(0) was oxidized by DBT sulfur during adsorption. Furthermore, Auger spectra verified that the adsorption of DBT on Cu(0) involved the formation of Cu(I) and Cu(II) species through coordination bonds. The adsorption capacity could be completely recovered via elution. This work sheds light on the removal of DBT in fuel oils with cost-effective efficient adsorbents.

Fabrication of composites with ultra-low chitosan loadings and the adsorption mechanism for lead ions.

Through a facile impregnation-precipitation strategy, chitosan was dispersed on bentonite to prepare an organic/inorganic hybrid composite for Pb2+ adsorption. The strong promotion effect of a small amount of highly dispersed chitosan on the Pb2+ adsorption capacity of clay minerals was unveiled. With a chitosan loading of 0.4 wt%, the experimental adsorption capacity reached 261.3 mg/g. The good dispersion of chitosan played a crucial role in the high capacity. The large proportion of mesopores in the adsorbent facilitated mass transfer, and thereby adsorption equilibrium states could be achieved within 15 s. The adsorption isotherms were consistent with the Freundlich expression. The Pb2+ adsorption capacity was suppressed with the addition of 150 ppm Ca2+ and almost eliminated in the presence of 150 ppm Mg2+. The adsorption enthalpy change was measured to be - 28.6 kJ/mol and Gibbs free energy change was in the range of - 18.4 to - 16.7 kJ/mol, indicating that this adsorption process was exothermic and spontaneous. The FTIR and XPS results demonstrated that the amino groups on chitosan could bond with Pb2+, and contributed to the high adsorption capacity. DFT calculation results showed that the amino and hydroxyl groups in adjacent chitosan units could be tri-coordinated with Pb2+, and the energy of system was greatly decreased due to the coordination interaction.

Study on mechanism of chitosan degradation with hydrodynamic cavitation.

Hydrodynamic cavitation is an effective method for chitosan degradation, of which the mechanism directly determines the molecular weight distribution of degradation products. In this study, based on the Monte Carlo simulation and experimental results, the mechanism of chitosan degradation with hydrodynamic cavitation and molecular weight distribution of products were analyzed. The results showed that the algorithm established in the simulation could effectively analyze degradation mechanism and the factors that influenced degradation mechanism and molecular weight distribution of products. The degradation with hydrodynamic cavitation was caused by chemical and mechanical effects, of which the former dominated the degradation process. The outlet and inlet angles and throat length of the cavitator had major and minor influences on the degradation pattern, respectively. The chemical effect led to random cuts resulting in wide distribution of the products, while the mechanical effect led to central cuts resulting in narrow distribution of the products. With more central cuts, the slide-shaped molecular weight distribution curve of degradation products was gradually transferred into a bell-shaped curve. These results provide instructions for researches on the molecular weight distribution of chitosan products degraded with hydrodynamic cavitation.

N2O profiles in the enhanced CANON process via long-term N2H4 addition: minimized N2O production and the influence of exogenous N2H4 on N2O sources.

Production of the greenhouse gas nitrous oxide (N2O) from the completely autotrophic nitrogen removal over nitrite (CANON) process is of growing concern. In this study, the effect of added hydrazine (N2H4) on N2O production during the CANON process was investigated. Long-term trace N2H4 addition minimized N2O production (0.018% ± 0.013% per unit total nitrogen removed) and maintaining high nitrogen removal capacity of CANON process (nitrogen removal rate and TN removal efficiency was 450 ± 60 mg N/L/day and 71 ± 8%, respectively). Ammonium oxidizing bacteria (AOB) was the main N2O producer. AOB activity inhibition by N2H4 decreased N2O production during aeration, and the N2H4 concentration was negatively correlated with N2O production rate in NH4+ oxidation via AOB, whereas N2O production was facilitated under anaerobic conditions because hydroxylamine (NH2OH) production was accelerated due to anammox bacteria (AnAOB) activity strengthen via N2H4. Added N2H4 completely degraded in the initial aeration phases of the CANON SBR, during which some N2H4 intensified anammox for total nitrogen removal to eliminate N2O production from nitrifier denitrification (ND) by anammox-associated, while the remaining N2H4 competed with NH2OH for hydroxylamine oxidoreductase (HAO) in AOB to inhibit intermediates formation that result in N2O production via NH2OH oxidation (HO) pathway, consequently decreasing total N2O production.