Activation of 2D titanate nanosheet photocatalysts by nitrogen doping and solution plasma processing.

Novel two-dimensional (2D) oxides are of great interest for photocatalysis because of their superlative physical features, namely, large surface areas, short charge diffusion pathways, high crystallinity and easy surface modification. However, most 2D oxides suffer from weak visible light absorption and severe photogenerated carrier recombination. Nitrogen doping can successfully narrow the bandgap of 2D oxides but can hardly improve the charge separation. In this work, we pre-dope nitrogen into 2D titanate nanosheets (HTiO), followed by surface processing with solution plasma. By dual modification of nitrogen doping and solution plasma processing (SPP), the modified 2D titanate nanosheets (N-HTiO-SPP) display broad absorption extending to the visible light region and the healing of oxygen vacancies brought about by nitrogen doping. Compared with HTiO and nitrogen doped titanate (N-HTiO), a higher removal rate and mineralization rate towards the photocatalytic degradation of acetaldehyde were achieved over N-HTiO-SPP under solar light. This work provides a powerful way to activate 2D wide bandgap semiconductors for enhanced photocatalytic activity.

Double knockout of FFAR4 and FGF21 aggravates metabolic disorders in mice.

Several investigations have examined the involvement of free fatty acid receptor 4 (FFAR4) in metabolic disorders, but its action remains controversial. To investigate whether endogenous fibroblast growth factor 21 (FGF21)-mediated signaling controls the metabolic status in FFAR4-deficient mice, we generated FFAR4/FGF21 double knockout (DKO) mice. We also evaluated the role of FGF21 on glucose and lipid metabolism in FFAR4 KO mice fed a high-fat diet. Levels of FGF21 were significantly increased in FFAR4-deficient mice and double deletion of FGF21 and FFAR4 led to severe metabolic disorders. Additionally, FFAR4/FGF21 DKO mice displayed metabolic abnormalities that may be caused by decreased energy expenditure. Collectively, this study characterized the effects of endogenous FGF21, which acts as a master feedback regulator in the absence of FFAR4.

Synergy of Adsorption and Photocatalytic Reduction for Efficient Removal of Cr(VI) with Polyvinylidene Fluoride@Polyvinyl Alcohol-FeC2O4/Bi2.15WO6.

Although the photocatalytic reduction of Cr(VI) to Cr(III) by traditional powder photocatalysts is a promising method, the difficulty and poor recovery of photocatalysts from water hinder their wide practical applications. Herein, we present that FeC2O4/Bi2.15WO6 (FeC2O4/BWO) composites were tightly bonded to modified polyvinylidene fluoride (PVDF) membranes by chemical grafting with the aid of polyvinyl alcohol (PVA) to form photocatalytic composite membranes (PVDF@PVA-FeC2O4/BWO). The contact angle of PVDF@PVA-FeC2O4/BWO (0.06 wt % of FeC2O4/BWO) is 48.0°, which is much lower than that of the pure PVDF membrane (80.5°). Meanwhile, the permeate flux of 61.43 g m-2 h-1 and water flux of 250.60 L m-2 h-1 were observed for PVDF@PVA-FeC2O4/BWO composite membranes. The tensile strength of composite membranes reached 48.84 MPa, which was 9.8 times higher than that of PVDF membrane. It was found that the PVDF@PVA-FeC2O4/BWO membrane exhibited excellent photocatalytic Cr(VI) reduction performance under both simulated and real sunlight irradiation. The adsorption for Cr(VI) by PVDF@PVA-FeC2O4/BWO can reach 47.6% in the dark process within 30 min, and the removal percentage of Cr(VI) could reach 100% with a rate constant k value of 0.2651 min-1 after 10 min of light exposure, indicating a synergistic effect of adsorption and photoreduction for Cr(VI) removal by the composite membrane. The PVDF@PVA-FeC2O4/BWO membrane had good stability and reusability after seven consecutive cycles. Most importantly, the influences of foreign ions on Cr(VI) reduction were investigated to mimic real sewage, which revealed that no obvious adverse effects can be found with the presence of common foreign ions in sewage. The photocatalytic membrane material developed in this study provides a new idea for treating Cr(VI)-containing wastewater and has a more significant application prospect.

Ethanol Solution Plasma Loads Carbon Dots onto 2D HNb3O8 for Enhanced Photocatalysis.

Layered metal oxoacids hold potential as photocatalysts due to their facile exfoliation to two-dimensional (2D) nanosheets with a large surface area and a short migration distance for photoexcited charge carriers. However, the utilization of electrons in photocatalytic processes is restricted by the competitive trapping of electrons by metal ions. In this work, we attempt to improve the utilization of photogenerated electrons over exfoliated HNb3O8 nanosheets by solution plasma activation. On dispersing exfoliated HNb3O8 nanosheets in ethanol solution plasma, the defects in HNb3O8 can be engineered, and carbon dots (CDs) can be anchored on the surface of HNb3O8 nanosheets in situ. In comparison with pristine HNb3O8 nanosheets, the rate of photocatalytic hydrogen evolution can be increased by 317.7 times over the HNb3O8/C heterojunction, and the apparent quantum efficiency of hydrogen production can be as high as 5.05%. The reason for the high photocatalytic performance is explored by the comparison of activation between plasma-in-ethanol and plasma-in-water, which reveals that CD anchoring and defect engineering indeed promote charge separation and hence lead to enhanced photocatalytic activity. This work provides an alternative approach to synthesize CDs and activate 2D-layered compounds with MO6 (M = Nb, Ti, and W) octahedral building blocks in the host layer for enhanced photocatalytic evolution of hydrogen.

Photocatalytic reduction of Cr(VI) by Bi2.15WO6 complexed with polydopamine: Contribution of the ligand-to-metal charge transfer path.

Photocatalytic reduction of Cr(VI) in water environments attracts more attention; however, the mechanisms involved in this process have not been clearly elucidated yet. In this study, the photocatalytic reduction of Cr(VI) by polydopamine modified Bi2.15WO6 (PDA/BWO) under visible light was conducted. Kinetics results show that PDA apparently accelerates the reduction of Cr(VI). The quasi-first-order kinetic constant of Cr(VI) reduction by 5PDA/BWO is 70.0 times that of the original BWO, reaching 0.070 min-1. X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and Raman analyses confirm the formation of ligand-to-metal charge transfer (LMCT) complex [Bi(III)OC] between PDA and BWO. The formed Bi(III)OC complex enhances visible light response and narrows the bandgap of PDA/BWO. The photoelectrochemical and photoluminescent characterization further reveals that the formed Bi(III)OC complex inhibits the recombination of carriers, thus enhancing the photocatalytic reactivity of PDA/BWO. Electrons, are derived from three paths, including dye sensitization, LMCT and bandgap excitation, contribute to Cr(VI) reduction by PDA/BWO. This study provides new insights on the paths of Cr(VI) reduction by PDA/BWO under visible light.

Effectiveness and safety of the improved mini-incision surgery for osmidrosis treatment.

BACKGROUND: As the mainstream treatment of axillary osmidrosis, surgical treatment is still limited by various complications, such as paresthesia, scars, local infection, hematoma, flap necrosis, and long recovery time. In this study, we tried to adopt the improved mini-incision surgery for osmidrosis treatment. OBJECTIVES: The paper aims to evaluate the clinical effectiveness and safety of the improved mini-incision surgery for axillary osmidrosis treatment. PATIENTS/METHODS: Clinical series of patients underwent improved mini-incision surgery were retrospectively reviewed. Dates of complications, including paresthesia, scars, infection, hematoma, skin necrosis, and recurrence were analyzed. RESULTS: Among 61 cases, 58 cases had a preoperative osmidrosis score of 3 and 3 cases had a preoperative score of 2; while 13 cases had a postoperative osmidrosis score of 0, 43 cases had a postoperative score of 1 and 5 cases had a postoperative score of 2, significantly lower than that before (p < 0.001). A total of 12 axillae complications occurred, 2 axillae (1.6%) had paresthesia; 5 axillae (4.1%) had hematoma; 2 axillae (1.6%) had local flap necrosis due to hematoma; and 3 axillae (2.4%) had hypertrophic scars. CONCLUSIONS: The results showed that the improved mini-incision surgery was safe and effective for osmidrosis treatment.

W-Doped TiO2 for photothermocatalytic CO2 reduction.

TiO2 is one of the most widely used photocatalysts and photothermocatalysts. Tailoring their structure and electronic properties is crucial for the design of high-performance TiO2 catalysts. Herein, we report a strategy to significantly enhance the performance of TiO2 in the photothermocatalytic reduction of CO2 by doping high crystalline nano-TiO2 with tungsten. A variety of tungsten doping concentrations ranging from 2% to 10% were tested and they all showed enhanced catalytic activities. The 4% W-doped TiO2 exhibited the highest activity, which was 3.5 times greater than that of the undoped TiO2 reference. Structural characterization of these W-doped TiO2 catalysts indicated that W was successfully doped into the TiO2 lattice at relatively low dopant concentration. Synchrotron X-ray absorption spectroscopy at both the W L3- and Ti K-edges was further used to provide insight into the local structure and bonding properties of the catalysts. It was found that the replacement of Ti with W led to the formation of Ti vacancies in order to maintain the charge neutrality. Consequently, dangling oxygen and oxygen vacancies were produced that acted as catalytically active sites for the CO2 reduction. As the W doping concentration increased from 2% to 4%, more such active sites were generated which thus resulted in the enhancement of the catalytic activity. When the W doping concentration was further increased to 10%, the extra W species that cannot replace the Ti in the lattice aggregated to form WO3. Due to the lower conduction band of WO3, the catalytic O sites were deactivated and CO2 reduction was inhibited. This work presents a useful strategy for the development of highly efficient catalysts for CO2 reduction as well as new insights into the catalytic mechanism in cation-doped TiO2 photothermocatalysis.

Peak compression in linear gradient elution liquid chromatography.

An expression for peak compression factor based on temporal peak widths is proposed which can be measured directly. The relationship between it and peak compression factor based on spatial peak widths is given. The experimental data presented in the Neue's work are reevaluated. The peak compression factor is recalculated by taking into account the curvature in the plot of logarithmic retention factor (lnk) vs. mobile phase composition (φ) and the variation in plate height (H) with φ. The lnk vs. φ plot is accounted for by quadratic solvent strength model (QSSM). The lnH vs. φ plot is accounted for by QSSM and a quadratic equation that accounts for the plot of logarithmic peak width obtained under isocratic elution (lnWI) vs. φ. By taking these two factors into account, the discrepancy between experimental and predicted values of peak width is reduced. This result confirms the Neue's conclusion that the anomalous peak broadening reported previously may be an artifact of the procedure to determine the theoretical value of peak width. Moreover, by assuming linear gradient elution, constant column efficiency, and general solvent strength, the relationship between peak compression factors obtained under ideal and real situation respectively is discussed.

Influence of the pre-elution of solute in initial mobile phase on retention time and peak compression under linear gradient elution.

Under gradient elution the solute will firstly migrate in initial mobile phase due to dwelling time (tD) of the system. The pre-elution of solute in initial mobile phase can be accounted for by a dimensionless value of tD/(t0kφ0), where t0 and kφ0 denote dead time and retention factor in initial mobile phase, respectively. The influence of tD/(t0kφ0) on retention time (tR) and peak compression factor (G) are discussed under linear gradient elution. A general expression for G is proposed, and two analytical forms of it which are suited for linear solvent strength model (LSSM) and quadratic solvent strength model (QSSM) respectively are presented. The well-known Poppe equation for G which is derived under LSSM is extended by taking tD/(t0kφ0) into account. The expression for G under QSSM takes into account the curvature in the plot of logarithmic retention factor vs. mobile phase composition. By taking twelve compounds degraded from lignin as analytes, the experimental and predicted chromatograms are found to be well consistent. It is shown that tD/(t0kφ0) has more effects on the prediction of tR than that of G.

Enhanced protopanaxadiol production from xylose by engineered Yarrowia lipolytica.

BACKGROUND: As renewable biomass, lignocellulose remains one of the major choices for most countries in tackling global energy shortage and environment pollution. Efficient utilization of xylose, an important monosaccharide in lignocellulose, is essential for the production of high-value compounds, such as ethanol, lipids, and isoprenoids. Protopanaxadiol (PPD), a kind of isoprenoids, has important medical values and great market potential. RESULTS: The engineered protopanaxadiol-producing Yarrowia lipolytica strain, which can use xylose as the sole carbon source, was constructed by introducing xylose reductase (XR) and xylitol dehydrogenase (XDH) from Scheffersomyces stipitis, overexpressing endogenous xylulose kinase (ylXKS) and heterologous PPD synthetic modules, and then 18.18 mg/L of PPD was obtained. Metabolic engineering strategies such as regulating cofactor balance, enhancing precursor flux, and improving xylose metabolism rate via XR (K270R/N272D) mutation, the overexpression of tHMG1/ERG9/ERG20 and transaldolase (TAL)/transketolase (TKL)/xylose transporter (TX), were implemented to enhance PPD production. The final Y14 strain exhibited the greatest PPD titer from xylose by fed-batch fermentation in a 5-L fermenter, reaching 300.63 mg/L [yield, 2.505 mg/g (sugar); productivity, 2.505 mg/L/h], which was significantly higher than the titer of glucose fermentation [titer, 167.17 mg/L; yield, 1.194 mg/g (sugar); productivity, 1.548 mg/L/h]. CONCLUSION: The results showed that xylose was more suitable for PPD synthesis than glucose due to the enhanced carbon flux towards acetyl-CoA, the precursor for PPD biosynthetic pathway. This is the first report to produce PPD in Y. lipolytica with xylose as the sole carbon source, which developed a promising strategy for the efficient production of high-value triterpenoid compounds.

Yarrowia lipolytica construction for heterologous synthesis of α-santalene and fermentation optimization.

Sandalwood oil is a valuable resource derived from Santalum album. It has antibacterial, cosmetic, and sedative effects. α-Santalene is the precursor of α-santalol, the main component of sandalwood oil. Yarrowia lipolytica is an oleaginous yeast, which has been metabolically engineered to produce valuable compounds such as terpenoids and biofuel. This study presents a method for the heterologous synthesis of α-santalene by Y. lipolytica. Using Y. lipolytica ATCC 201249, a codon-optimized plant-origin α-santalene synthase (STS) was integrated into the genome, and a yield of 5.19 mg/L α-santalene was obtained after fermentation. Upstream genes in the MVA pathway (ERG8, ERG10, ERG12, ERG13, ERG19, ERG20, HMG1, and tHMG1) were overexpressed, and we found that the key genes ERG8, HMG1, and tHMG1 can increase the supply of FPP and the yield of α-santalene. ERG8 and HMG1 were overexpressed in multiple-copy formats, and the plasmid pERG8HMG1 and ERG8-HMG1 expression modules were optimized as single-copy and multiple-copy formats, respectively. The overexpression of single-copy plasmid pERG8HMG1 led to α-santalene yield of 13.31 mg/L. The optimal feeding strategy was determined by initial carbon source concentration optimizations and five feeding methods. Using 50 g/L glucose as the initial carbon source, maintaining the carbon source concentration at 5-20 g/L during the feeding process is most conducive to increased production. These results were verified in a 5-L fermenter by batch and fed-batch fermentation. The OD of fed-batch fermentation broth reached 79.09, and the production of α-santalene reached 27.92 mg/L; 5.38 times of the initial yield, without by-products farnesol and trans-α-bergamotene.

Production of Triterpene Ginsenoside Compound K in the Non-conventional Yeast Yarrowia lipolytica.

Compound K (CK) is a rare, tetracyclic, triterpenoid compound with important medical properties, such as antitumor and anti-inflammatory activities. Herein, an efficient biosynthetic pathway of CK was constructed in metabolically engineered Yarrowia lipolytica for the first time, and the engineered strain, YL-CK0, produced 5.1 mg/L CK. The production of CK was further increased by 5.96-fold to 30.4 mg/L with overexpression of key genes in the MVA pathway and fusion of cytochrome P450 monooxygenase (PPDS) and NADPH-P450 reductase. Finally, 161.8 mg/L CK production was achieved by fed-batch fermentation in a 5 L fermenter using the strain YL-MVA-CK. To the best of our knowledge, this is the first report on heterologous CK synthesis with the highest titer in Y. lipolytica. This study demonstrates the feasibility of producing high-value triterpenoid compounds using Y. lipolytica as a platform.

[Evaluation of continuous curvilinear buccal-cervical incision in combined radical resection of buccal cancer].

PURPOSE: To evaluate the clinical effect of continuous curvilinear buccal-cervical incision in combined radical resection of buccal cancer. METHODS: From January 2015 to December 2018, a total of 87 patients with buccal cancer were collected, of whom 42 underwent continuous curvilinear buccal-cervical incision (experimental group) and 45 underwent conventional cervical T shaped incision combined with a buccal incision (control group). Exposure of surgical filed in two groups was evaluated. The length of incision, duration of radical resection, and the incidence of postoperative complications were compared between two groups. The patients were followed-up for 7-43 months. Modified vancouver scar scale (VSS) and University of Washington Quality of Life (UW-QOL) were used to evaluate the postoperative scar and quality of life in both groups. Statistical analysis was performed on the data using SPSS 22.0 software package. RESULTS: The length of the incision in the experimental group was (36.40±5.08) cm, which was shorter than that of the control group (39.93±5.22) cm. Duration of combined radical resection in the experimental group was shorter than that of the control group. The incidence of neck complications in the experimental group was lower than that of the control group. The postoperative scar assessment and quality of life of the experimental group were better than that of the control group. The difference was statistically significant (P<0.05). There was no significant difference between the two groups in terms of the exposure of the surgical field, postoperative recurrence and metastasis rate. CONCLUSIONS: Continuous curvilinear buccal-cervical incision has good exposure of the surgical field and shorter duration of radical resection, which ensures en bloc resection of tumor and cervical lymph nodes. It limits the formation of skin cicatrix, reduces the occurrence of postoperative complications and results in a good aesthetic and functional effect, therefore it is a recommended incision for clinical practice.

"Perfect" designer chromosome V and behavior of a ring derivative.

Perfect matching of an assembled physical sequence to a specified designed sequence is crucial to verify design principles in genome synthesis. We designed and de novo synthesized 536,024-base pair chromosome synV in the "Build-A-Genome China" course. We corrected an initial isolate of synV to perfectly match the designed sequence using integrative cotransformation and clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9)-mediated editing in 22 steps; synV strains exhibit high fitness under a variety of culture conditions, compared with that of wild-type V strains. A ring synV derivative was constructed, which is fully functional in Saccharomyces cerevisiae under all conditions tested and exhibits lower spore viability during meiosis. Ring synV chromosome can extends Sc2.0 design principles and provides a model with which to study genomic rearrangement, ring chromosome evolution, and human ring chromosome disorders.

Optimization of a cytochrome P450 oxidation system for enhancing protopanaxadiol production in Saccharomyces cerevisiae.

Ginsenosides, the major bioactive components of Panax ginseng, are regarded as promising high-value pharmaceutical compounds. In ginseng, ginsenosides are produced from their precursor protopanaxadiol. Recently, an artificial biosynthetic pathway of protopanaxadiol was built in Saccharomyces cerevisiae by introducing a P. ginseng dammarenediol-II synthase, a P. ginseng cytochrome P450-type protopanaxadiol synthase (PPDS), and a Arabidopsis thaliana NADPH-cytochrome P450 reductase (ATR1). In this engineered yeast strain, however, the low metabolic flux through PPDS resulted in a low productivity of protopanaxadiol. Moreover, health of the yeast cells was significantly affected by reactive oxygen species released by the pool coupling between PPDS and ATR1. To overcome the obstacles in protopanaxadiol production, PPDS was modified through transmembrane domain truncation and self-sufficient PPDS-ATR1 fusion construction in this study. The fusion enzymes conferred approximately 4.5-fold increase in catalytic activity, and 71.1% increase in protopanaxadiol production compared with PPDS and ATR1 co-expression. Our in vivo experiment indicated that the engineered yeast carrying fusion protein effectively converted 96.8% of dammarenediol-II into protopanaxadiol. Protopanaxadiol production in a 5 L bioreactor in fed-batch fermentation reached 1436.6 mg/L. Our study not only improved protopanaxadiol production in yeast, but also provided a generic method to improve activities of plant cytochrome P450 monooxygenases. This method is promising to be applied to other P450 systems in yeast. Biotechnol. Bioeng. 2016;113: 1787-1795. © 2016 Wiley Periodicals, Inc.

Heterologous biosynthesis of triterpenoid dammarenediol-II in engineered Escherichia coli.

OBJECTIVES: To achieve heterologous biosynthesis of dammarenediol-II, which is the precursor of dammarane-type tetracyclic ginsenosides, by reconstituting the 2,3-oxidosqualene-derived triterpenoid biosynthetic pathway in Escherichia coli. RESULTS: By the strategy of synthetic biology, dammarenediol-II biosynthetic pathway was reconstituted in E. coli by co-expression of squalene synthase (SS), squalene epoxidase (SE), NADPH-cytochrome P450 reductase (CPR) from Saccharomyces cerevisiae, and SE from Methylococcus capsulatus (McSE), NADPH-cytochrome P450 reductase (CPR) from Arabidopsis thaliana. Sequences of transmembrane domains were truncated if necessary in each of the genes. Different sources of SE/CPR combinations were tested, during which two CPRs were detected to be new reductase partners of McSE. When the gene encoding dammarenediol-II synthase was co-expressed with the 2,3-oxidosqualene expression modules, dammarenediol-II was detected and the production was 8.63 mg l(-1) in E. coli under the shake-flask conditions. CONCLUSIONS: Two E. coli chassis for production of dammarenediol-II were established which could be potentially applied in other triterpenoid production in E. coli when different oxidosqualene cyclases (OSCs) introduced into the system.

Suitable extracellular oxidoreduction potential inhibit rex regulation and effect central carbon and energy metabolism in Saccharopolyspora spinosa.

BACKGROUND: Polyketides, such as spinosad, are mainly synthesized in the stationary phase of the fermentation. The synthesis of these compounds requires many primary metabolites, such as acetyl-CoA, propinyl-CoA, NADPH, and succinyl-CoA. Their synthesis is also significantly influenced by NADH/NAD+. Rex is the sensor of NADH/NAD+ redox state, whose structure is under the control of NADH/NAD+ ratio. The structure of rex controls the expression of many NADH dehydrogenases genes and cytochrome bd genes. Intracellular redox state can be influenced by adding extracellular electron acceptor H2O2. The effect of extracellular oxidoreduction potential on spinosad production has not been studied. Although extracellular oxidoreduction potential is an important environment effect in polyketides production, it has always been overlooked. Thus, it is important to study the effect of extracellular oxidoreduction potential on Saccharopolyspora spinosa growth and spinosad production. RESULTS: During stationary phase, S. spinosa was cultured under oxidative (H2O2) and reductive (dithiothreitol) conditions. The results show that the yield of spinosad and pseudoaglycone increased 3.11 fold under oxidative condition. As H2O2 can be served as extracellular electron acceptor, the ratios of NADH/NAD+ were measured. We found that the ratio of NADH/NAD+ under oxidative condition was much lower than that in the control group. The expression of cytA and cytB in the rex mutant indicated that the expression of these two genes was controlled by rex, and it was not activated under oxidative condition. Enzyme activities of PFK, ICDH, and G6PDH and metabolites results indicated that more metabolic flux flow through spinosad synthesis. CONCLUSION: The regulation function of rex was inhibited by adding extracellular electron acceptor-H2O2 in the stationary phase. Under this condition, many NADH dehydrogenases which were used to balance NADH/NAD+ by converting useful metabolites to useless metabolites and unefficient terminal oxidases (cytochrome bd) were not expressed. So lots of metabolites were not waste to balance. As a result, un-wasted metabolites related to spinosad and PSA synthesis resulted in a high production of spinosad and PSA under oxidative condition.