Enzymatic Electrosynthesis of Glycine from CO2 and NH3.

Enzymatic electrosynthesis has gained more and more interest as an emerging green synthesis platform, particularly for the fixation of CO2 . However, the simultaneous utilization of CO2 and a nitrogenous molecule for the enzymatic electrosynthesis of value-added products has never been reported. In this study, we constructed an in vitro multienzymatic cascade based on the reductive glycine pathway and demonstrated an enzymatic electrocatalytic system that allowed the simultaneous conversion of CO2 and NH3 as the sole carbon and nitrogen sources to synthesize glycine. Through effective coupling and the optimization of electrochemical cofactor regeneration and the multienzymatic cascade reaction, 0.81 mM glycine was yielded with a highest reaction rate of 8.69 mg L-1 h-1 and faradaic efficiency of 96.8 %. These results imply a promising alternative for enzymatic CO2 electroreduction and expand its products to nitrogenous chemicals.

Capillarisin protects SH-SY5Y cells against bupivacaine-induced apoptosis via ROS-mediated PI3K/PKB pathway.

AIMS: Bupivacaine, a common local anesthetic, can induce neurotoxicity and neurological complications. Capillarisin, a bioactive ingredient of Artemisia capillaris root extracts, has been reported to protect SH-SY5Y cells against oxidative stress-mediated neuronal cell death. Nevertheless, the effects of capillarisin on bupivacaine-induced neurotoxicity in SH-SY5Y cells remain unclear. MAIN METHODS: Cell viability, lactate dehydrogenase (LDH) release, reactive oxygen species (ROS) production, and apoptosis were detected. Malondialdehyde (MDA) content, glutathione peroxidase (GSH-Px), superoxide dismutase (SOD) and catalase (CAT) activities were measured for evaluation of oxidative stress. Western blot was performed to detect the changes of phosphatidylinositol-3-kinase (PI3K)/protein kinase B (PKB) pathway, and expression of cleaved poly ADP ribose polymerase (PARP), cleaved caspase-3, glucose-regulated protein 78 (GRP78) and C/EBP homologous protein (CHOP). Activities of mitochondrial respiratory chain complexes I-III and adenosine triphosphate (ATP) content were measured to evaluate mitochondrial damage. KEY FINDINGS: Bupivacaine treatment dose-dependently reduced cell viability, increased LDH release, and induced ROS production and PI3K/PKB pathway inactivation in SH-SY5Y cells, which were overturned by capillarisin treatment. Capillarisin inhibited bupivacaine-induced apoptosis in SH-SY5Y cells by decreasing cleaved PARP and cleaved caspase-3 expression. Capillarisin inhibited bupivacaine-induced oxidative stress, decrease of mitochondrial respiratory chain complex I, II, and III activities and ATP content, and increase of GRP78 and CHOP expression in SH-SY5Y cells. However, treatment with LY294002 abolished the effects of capillarisin on bupivacaine-induced neurotoxicity in SH-SY5Y cells. SIGNIFICANCE: Capillarisin protected SH-SY5Y cells against bupivacaine-induced apoptosis by inhibiting oxidative stress, mitochondrial injury, and endoplasmic reticulum stress via ROS-mediated of PI3K/PKB pathway.

Smart Oral Administration of Polydopamine-Coated Nanodrugs for Efficient Attenuation of Radiation-Induced Gastrointestinal Syndrome.

High-dose ionizing radiation can lead to death from the unrecoverable damage of the gastrointestinal tract, especially the small intestine. Until now, the lack of predilection for the small intestine and rapid clearance by digestive fluids limit the effects of conventional radioprotective formulations. Herein, an innovative radioprotective strategy is developed for attenuating gastrointestinal syndrome by smart oral administration nanodrugs. The nanodrug is first engineered by encapsulating thalidomide into chitosan-based nanoparticles, and then coated with polydopamine. The behaviors of gastric acid-resistance, and pH-switchable controlled release in the small intestine enhance the oral bioavailability of the pyroptosis inhibitor thalidomide. In a mouse model, nanodrugs demonstrate prolonged small intestinal residence time and accessibility to the crypt region deep in the mucus. Furthermore, the nanodrugs ameliorate survival rates of C57BL/6J mice irradiated by 14 Gy of subtotal body irradiation and also maintain their epithelial integrity. This work may provide a promising new approach for efficiently attenuating lethal radiation-induced gastrointestinal syndrome and add insights into developing nanodrug-based therapies with improved efficacy and minimum side effects.

Engineering unnatural methylotrophic cell factories for methanol-based biomanufacturing: Challenges and opportunities.

Methanol is a very promising feedstock alternative to sugar-based raw materials for biomanufacturing because it does not compete with food production, is abundant and potentially sustainable in the future. Although methylotrophic fermentations have been practiced for decades, their applications are limited by technical drawbacks and insufficient knowledge of the physiology and metabolic regulation of native methylotrophs. Synthetic biology offers great opportunities for engineering efficient methylotrophic microbial cell factories by enabling non-methylotrophic model organisms to utilize methanol via the introduction of C1 utilization pathways. This review critically comments C1 metabolism with a focus on comparing different methanol-utilization pathways in light of biomanufacturing, and highlights recent advances in the engineering of synthetic methylotrophs. Most importantly, the unique challenges in the engineering process and possible solutions are also discussed in detail.

Enhancing the Energy Density of Tricritical Ferroelectrics for Energy Storage Applications.

Recently, tricritical ferroelectrics have been drawn tremendous attention, owing to their ultrahigh dielectric permittivities of up to εr > 5 × 104, and their consideration for prototype materials in the development of high-performance energy storage devices. Nevertheless, such a materials system suffers from the disadvantage of low breakdown strength, which makes its energy density far from the satisfactory level for practical application. In this paper, a material-modification approach has been reported, for improving the dielectric strength for tricritical ferroelectric materials Ba(Ti1-xSnx)O3 (BTS) through doping with Bi1.5ZnNb1.5O7 (BZN) additives. The results suggest that the electric strength has been largely improved in the modified tricritical ferroelectric material (BTSx-yBZN), and the associated energy density reaches Ue = 1.15 J/cm³. Further microstructure investigation indicates that the modified tricritical ferroelectric material exhibits homogenous fine grains with perovskite structure in crystal symmetry, and the BZN may help to form a special structure that could enhance the breakdown strength. The findings may advance the material design and development of high-energy storage materials.

Improved production of trans-4-hydroxy-l-proline by chromosomal integration of the Vitreoscilla hemoglobin gene into recombinant Escherichia coli with expression of proline-4-hydroxylase.

trans-4-Hydroxy-l-proline (Hyp) is a chiral amino acid conventionally produced by acid hydrolysis of animal collagen, a process which involves the bottleneck problems of low efficiency and heavy environmental pollution. Biotransformation of l-proline into Hyp using recombinant whole-cell biocatalysis with proline-4-hydroxylase (P4H) is an environmentally-friendly alternative method. Since biohydroxylation of proline by whole cells is a high-oxygen-demand process, oxygen transfer needs to be improved. To solve this problem, the Vitreoscilla hemoglobin gene (vgb) was integrated into the chromosome of recombinant Escherichia coli expressing the P4H gene originally from Dactylosporangium sp. RH1. Expression of Vitreoscilla hemoglobin (VHb) resulted in a 94.4% increase of Hyp production in a 100-mL shaking flask culture compared to the same strain without VHb expression. Meanwhile in a fed-batch fermentation with a 1.4 L bioreactor, the expression of VHb led to an increase in Hyp production by 73.2% and biomass improved by 106%. We also found that acetic acid concentration was decreased by the expression of VHb during the fermentation. This work demonstrates that vgb chromosomal integration is an efficient way to improve Hyp production by enhancing oxygen transfer in recombinant E. coli.

Characterization of a novel Acinetobacter baumannii xanthine dehydrogenase expressed in Escherichia coli.

OBJECTIVE: To characterize a novel xanthine dehydrogenase (XDH) from Acinetobacter baumannii by recombinant expression in Escherichia coli and to assess its potential for industrial applications. RESULTS: The XDH gene cluster was cloned from A. baumannii CICC 10254, expressed heterologously in E. coli and purified to homogeneity. The purified recombinant XDH consisted of two subunits with the respective molecular weights of 87 kDa and 56 kDa according to SDS-PAGE. XDH catalysis was optimum at pH 8.5 and 40-45 °C, was stable under alkaline conditions (pH 7-11) and the half-inactivation temperature was 60 °C. The K m, turnover number and catalytic efficiency for xanthine were 25 µM, 69 s(-1) and 2.7 µM(-1) s(-1), respectively, which is an improvement over XDHs characterized previously. A. baumannii XDH is less than 50 % identical to previously identified XDH orthologs from other species, and is the first from the Acinetobacter genus to be characterized. CONCLUSION: The novel A. baumannii enzyme was found to be among the most active, thermostable and alkaline-tolerant XDH enzymes reported to date and has potential for use in industrial applications.