Balancing Redox Homeostasis to Improve l-Cysteine Production in Corynebacterium glutamicum.

l-Cysteine is a valuable sulfur-containing amino acid with applications across a wide range of fields. Recently, microbial fermentation has emerged as a method to produce l-cysteine. However, cellular redox stress from high levels of l-cysteine is a bottleneck for achieving efficient production. In this study, we aimed to facilitate l-cysteine biosynthesis by modulating cellular redox homeostasis through the introduction of the natural antioxidant astaxanthin in Corynebacterium glutamicum. To achieve this, we first introduced an exogenous astaxanthin synthesis module in C. glutamicum. Then, an l-cysteine-dependent autonomous bifunctional genetic switch was developed to dynamically regulate the l-cysteine and astaxanthin biosynthesis pathway to maintain cellular redox homeostasis. This regulation system achieved high biosynthesis of astaxanthin, which significantly facilitated l-cysteine production. Finally, engineered strain Cg-10 produced 8.45 g/L l-cysteine and 95 mg/L astaxanthin in a 5 L bioreactor, both of which are the highest reported levels in C. glutamicum.

Transcription factor OxyR regulates sulfane sulfur removal and L-cysteine biosynthesis in Corynebacterium glutamicum.

Sulfane sulfur, a collective term for hydrogen polysulfide and organic persulfide, often damages cells at high concentrations. Cells can regulate intracellular sulfane sulfur levels through specific mechanisms, but these mechanisms are unclear in Corynebacterium glutamicum. OxyR is a transcription factor capable of sensing oxidative stress and is also responsive to sulfane sulfur. In this study, we found that OxyR functioned directly in regulating sulfane sulfur in C. glutamicum. OxyR binds to the promoter of katA and nrdH and regulates its expression, as revealed via in vitro electrophoretic mobility shift assay analysis, real-time quantitative PCR, and reporting systems. Overexpression of katA and nrdH reduced intracellular sulfane sulfur levels by over 30% and 20% in C. glutamicum, respectively. RNA-sequencing analysis showed that the lack of OxyR downregulated the expression of sulfur assimilation pathway genes and/or sulfur transcription factors, which may reduce the rate of sulfur assimilation. In addition, OxyR also affected the biosynthesis of L-cysteine in C. glutamicum. OxyR overexpression strain Cg-2 accumulated 183 mg/L of L-cysteine, increased by approximately 30% compared with the control (142 mg/L). In summary, OxyR not only regulated sulfane sulfur levels by controlling the expression of katA and nrdH in C. glutamicum but also facilitated the sulfur assimilation and L-cysteine synthesis pathways, providing a potential target for constructing robust cell factories of sulfur-containing amino acids and their derivatives. IMPORTANCE C. glutamicum is an important industrial microorganism used to produce various amino acids. In the production of sulfur-containing amino acids, cells inevitably accumulate a large amount of sulfane sulfur. However, few studies have focused on sulfane sulfur removal in C. glutamicum. In this study, we not only revealed the regulatory mechanism of OxyR on intracellular sulfane sulfur removal but also explored the effects of OxyR on the sulfur assimilation and L-cysteine synthesis pathways in C. glutamicum. This is the first study on the removal of sulfane sulfur in C. glutamicum. These results contribute to the understanding of sulfur regulatory mechanisms and may aid in the future optimization of C. glutamicum for biosynthesis of sulfur-containing amino acids.

Effect of acupuncture in the acute phase of intracerebral hemorrhage on the prognosis and serum BDNF: a randomized controlled trial.

Background: Intracerebral hemorrhage (ICH) is a common cerebrovascular disease, with a high rate of disability. In the literature on Chinese traditional medicine, there is increasing evidence that acupuncture can help hematoma absorption and improve neurological deficits after cerebral hemorrhage. Brain-derived neurotrophic factor (BDNF), one of the most studied neurotrophic factors, is involved in a variety of neurological functions and plays an important role in brain injury recovery. We investigated the effect of acupuncture intervention in the acute phase of ICH on the prognosis and serum BDNF levels of several patient groups. Objective: To investigate the influence of acupuncture on the prognosis and brain-derived neurotrophic factor (BDNF) levels in patients in the acute phase of ICH. Methods: From November 2021 to May 2022, 109 subjects were consecutively enrolled, including patients with ICH, who were randomized into the acupuncture group (AG) and sham acupuncture group (SAG), and a control group (CG). The CG received the same acupuncture intervention as the AG, and the SAG received sham acupuncture, with 14 interventions in each group. The level of consciousness of patients with ICH was assessed and serum BDNF levels were measured in all three groups before the intervention and at 3 weeks after onset, and the level of consciousness and outcomes were assessed at 12 weeks after onset. Results: After the intervention, the level of consciousness of the AG improved significantly (P < 0.05); the BDNF level of only the AG increased significantly (P < 0.05); the changes in Glasgow Coma Scale (GCS) score and BDNF level were significantly greater in the AG than in the SAG (P < 0.05), especially for locomotion (P < 0.05). At 12 weeks post-onset, the AG showed better outcomes and recovery of consciousness than the SAG (P < 0.05).

Improving the Electron Transport Performance of TiO2 Film by Regulating TiCl4 Post-Treatment for High-Efficiency Carbon-Based Perovskite Solar Cells.

Titanium oxide (TiO2 ) has been widely used as an electron transport layer (ETL) in perovskite solar cells (PSCs). Typically, TiCl4 post-treatment is indispensable for modifying the surfaces of TiO2 ETL to improve the electron transport performance. However, it is challenging to produce the preferred anatase phase-dominated TiO2 by the TiCl4 post-treatment due to the higher thermodynamic stability of the rutile phase. In this work, a mild continuous pH control strategy for effectively regulating the hydrolysis process of TiCl4 post-treatment is proposed. As the weak organic base, urea has been demonstrated can maintain a moderate pH decrease during the hydrolysis process of TiCl4 while keeping the hydrolysis process relatively mild due to the ultra-weak alkalinity. The improved pH environment is beneficial for the formation of anatase TiO2 . Consequently, a uniform anatase-dominated TiO2 surface layer is formed on the mesoporous TiO2 , resulting in reduced defect density and superior band energy level. The interfacial charge recombination is effectively suppressed, and the charge extraction efficiency is improved simultaneously in the fabricated solar cells. The efficiency of the fabricated carbon electrode-based PSCs (C-PSCs) is improved from 16.63% to 18.08%, which is the highest for C-PSCs based on wide-bandgap perovskites.

Self-Driven Prenucleation-Induced Perovskite Crystallization Enables Efficient Perovskite Solar Cells.

Perovskite film with high crystal quality is fundamental to achieving high-performance solar cells. A fast nucleation process is crucial to improving the crystallization quality. Here, we propose a self-driven prenucleation strategy to achieve fast nucleation. This is realized through rational solvent design. The key characteristics of different solvents are systematically evaluated. Among them, formamide, with ultra-high dielectric constant, low Gutman donor number, and a high boiling point, is selected as the co-solvent. These unique characteristics render formamide a double-face solvent that is a good solvent for formamidinium iodide (FAI) and CsI while a poor solvent for PbI2 . As a result, formamide induces the self-driven prenucleation of PbI2 -DMSO seeding crystals and accelerates the nucleation, improving the crystalline quality of perovskite film. The efficiency of the hole transport layer-free carbon-based perovskite solar cells is boosted beyond 19 % for the first time.

Continuous CO2 capture and methanation over Ni-Ca/Al2O3 dual functional materials.

Although Ni-Ca-based dual functional materials (DFMs) have been examined for CO2 capture and reduction with H2 (CCR) for the synthesis of CH4, their performance has generally been investigated using single reactors in an oxygen-free environment. In addition, continuous CCR operations have scarcely been investigated. In this study, continuous CCR for the production of CH4 was investigated using a double reactor system over Al2O3-supported Ni-Ca DFMs in the presence of O2. We found that a high Ca loading (Ni(10)-Ca(30)/Al2O3, 10 wt% Ni, and 30 wt% CaO) was necessary for reaction efficiency under isothermal conditions at 450 °C. The optimized DFM exhibited an excellent performance (46% CO2 conversion, 45% CH4 yield, and 97% CH4 selectivity, respectively) and good stability over 24 h. The structure and CCR activity of Ni(10)-Ca(30)/Al2O3 were studied using X-ray diffraction (XRD), scanning transmission electron microscopy (STEM), energy-dispersive X-ray spectrometry (EDS), temperature-programmed desorption (TPD), and temperature-programmed surface reaction (TPSR) techniques.

The reducibility and oxidation states of oxide-supported rhenium: experimental and theoretical investigations.

The activity and stability of supported metal catalysts, which exhibit high efficiency and activity, are significantly influenced by the interactions between the metal and the support, that is, metal-support interactions (MSIs). Here, we report an investigation of the MSIs between supported rhenium (Re) and oxide supports such as TiO2, SiO2, Al2O3, MgO, V2O5, and ZrO2 using experimental and computational approaches. The reducibility of the Re species was found to strongly depend on the oxide support. Experimental studies including temperature-programmed reduction by H2 as well as Re L3- and L1-edge X-ray absorption near edge structure (XANES) analysis revealed that the valency of the Re species started to decrease upon H2 reduction in the 200-400 °C range, except for Re on MgO, where the shift occurred at temperatures above 500 °C. The dependence of the Re L3- and L1-edge XANES spectra of the oxide-supported Re catalysts on the size of Re was also examined.

[Cloning, expression and characterization of a new endo-ß-N-acetylglucosaminidase from Streptomyces alfalfae].

Endo-ß-N-acetylglucosaminidase is used widely in the glycobiology studies and industries. In this study, a new endo-ß-N-acetylglucosaminidase, designated as Endo SA, was cloned from Streptomyces alfalfae ACCC 40021 and expressed in Escherichia coli BL21 (DE3). The purified recombinant Endo SA exhibited the maximum activity at 35 ºC and pH 6.0, good thermo/pH stability and high specific activity (1.0×106 U/mg). It displayed deglycosylation activity towards different protein substrates. These good properties make EndoSA a potential tool enzyme and industrial biocatalyst.

Comparative Study of Moisture-Treated Pd@CeO2/Al2O3 and Pd/CeO2/Al2O3 Catalysts for Automobile Exhaust Emission Reactions: Effect of Core-Shell Interface.

In this article, moisture-treated Pd@CeO2/Al2O3 and Pd/CeO2/Al2O3 catalysts were synthesized and applied in automotive three-way catalytic (TWC) reactions. Compared to the Pd/CeO2/Al2O3 catalyst, the Pd@CeO2/Al2O3 core-shell catalyst had better TWC activities. Transmission electron microscopy (TEM) images and X-ray photoelectron spectra (XPS) showed excess PdO2 on the Pd and CeO2 interface of Pd@CeO2 nanoparticles. Fourier transform infrared (FT-IR) spectra analysis demonstrated the generation of the hydroperoxyl (*OOH) groups on the surface of the Pd@CeO2 nanoparticle. CO-diffuse reflectance Fourier transform (DRIFT) measurement suggested that the CO adsorbed on *OOH species contributed to the formation of CO2 and intermediate *COOH. NO-DRIFT results showed that more *NO2 species appeared on the moisture-treated Pd@CeO2 nanoparticle, which was the main active site in the automobile TWC reaction. These were the main factors contributing to the moisture-treated Pd@CeO2/Al2O3 catalyst's high catalytic activities. The collected data revealed the crucial role of the co-promoting effect of moisture and core-shell interface on TWC reactions over the Pd@CeO2/Al2O3 catalyst, which could be applied to other catalytic reactions.

Biochemical characterization of a ß-N-acetylhexosaminidase from Streptomyces alfalfae and its application in the production of N-acetyl-d-glucosamine.

N-Acetyl-d-glucosamine (GlcNAc) is a valuable monosaccharide widely used in the medical, agricultural, biofuel, and food industries. Its efficient and environment-friendly production depends on the binary system of ß-N-acetylhexosaminidase (HEX) and chitinase. In the present study, a HEX of glycoside hydrolasefamily 20 was identified in Streptomyces alfalfae ACCC40021, and was overexpressed in Escherichia coli. The purified recombinant SaHEX showed maximal activities at 60°C and pH 5.5, and retained stable up to 45°C. The enzyme not only exhibited broad substrate specificity including p-nitrophenyl ß-N-acetylglucosaminide, p-nitrophenyl ß-N-acetylgalactosaminide, chitooligosaccharides and colloidal chitin, but also had higher specific activities (up to 1149.7 ± 72.6 U/mg) towards natural and synthetic substrates. When combined with a commercial chitinase, it achieved a conversion rate of 93.7% from 1% of colloidal chitin to GlcNAc in 6 h, with the product purity of >98%. These excellent properties make SaHEX a potential enzyme candidate for the chitin conversion for various industrial purposes.

Precisely controlled synthesis of α-/ß-MnO2 materials by adding Zn(acac)2 as a phase transformation-inducing agent.

In this paper, we present an approach for the precisely controlled phase transformation of MnO2 in order to synthesise different compositions of α-/ß-MnO2 materials, by adding a trace amount of Zn(acac)2 as the phase transformation-inducing agent in a hydrothermal reaction. The single-atomic dispersion of Zn might reduce the barrier of phase transformation of δ-MnO2 to ß-MnO2. The ratio of the Zn species present in the single-atomic dispersions and nanoclusters might dominate the generation of α-MnO2 and ß-MnO2. The results of the oxygen reduction reactions indicate that the MnO2 materials have potential applications as promising catalysts in electrochemical catalysis.