Metabolic engineering allows development of microbial strains efficiently producing chemicals and materials, but it requires much time, effort, and cost to make the strains industrially competitive. ...Systems metabolic engineering, which integrates tools and strategies of systems biology, synthetic biology, and evolutionary engineering with traditional metabolic engineering, has recently been used to facilitate development of high-performance strains. The past decade has witnessed this interdisciplinary strategy continuously being improved toward the development of industrially competitive overproducer strains. In this article, current trends in systems metabolic engineering including tools and strategies are reviewed, focusing on recent developments in selection of host strains, metabolic pathway reconstruction, tolerance enhancement, and metabolic flux optimization. Also, future challenges and prospects are discussed.
Systems metabolic engineering, which integrated systems biology, synthetic biology, and evolutionary engineering with traditional metabolic engineering, is facilitating the development of high performance strains.
More diverse microorganisms are being used as production host strains, supported by the new genetic tools and strategies.
Recent advances in biosynthetic/semisynthetic design strategies are expanding the portfolio of products that can be produced biologically.
Evolutionary engineering tools and strategies are facilitating the improvement of strain and enzyme performances.
Advances in tools and strategies of omics, in silico metabolic simulation, genetic and genomic engineering, and high-throughput screening are accelerating optimization of metabolic fluxes for the enhanced production of target bioproducts.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Increased grain yield will be critical to meet the growing demand for food, and could be achieved by delaying crop senescence. Here, via quantitative trait locus (QTL) mapping, we uncover the genetic ...basis underlying distinct life cycles and senescence patterns of two rice subspecies, indica and japonica. Promoter variations in the Stay-Green (OsSGR) gene encoding the chlorophyll-degrading Mg
-dechelatase were found to trigger higher and earlier induction of OsSGR in indica, which accelerated senescence of indica rice cultivars. The indica-type promoter is present in a progenitor subspecies O. nivara and thus was acquired early during the evolution of rapid cycling trait in rice subspecies. Japonica OsSGR alleles introgressed into indica-type cultivars in Korean rice fields lead to delayed senescence, with increased grain yield and enhanced photosynthetic competence. Taken together, these data establish that naturally occurring OsSGR promoter and related lifespan variations can be exploited in breeding programs to augment rice yield.
Bacterial cellulose nanofiber (CNF) is a polymer with a wide range of potential industrial applications. Several Komagataeibacter species, including Komagataeibacter xylinus as a model organism, ...produce CNF. However, the industrial application of CNF has been hampered by inefficient CNF production, necessitating metabolic engineering for the enhanced CNF production. Here, we present complete genome sequence and a genome‐scale metabolic model KxyMBEL1810 of K. xylinus DSM 2325 for metabolic engineering applications. Genome analysis of this bacterium revealed that a set of genes associated with CNF biosynthesis and regulation were present in this bacterium, which were also conserved in another six representative Komagataeibacter species having complete genome information. To better understand the metabolic characteristics of K. xylinus DSM 2325, KxyMBEL1810 was reconstructed using genome annotation data, relevant computational resources and experimental growth data generated in this study. Random sampling and correlation analysis of the KxyMBEL1810 predicted pgi and gnd genes as novel overexpression targets for the enhanced CNF production. Among engineered K. xylinus strains individually overexpressing heterologous pgi and gnd genes, either from Escherichia coli or Corynebacterium glutamicum, batch fermentation of a strain overexpressing the E. coli pgi gene produced 3.15 g/L of CNF in a complex medium containing glucose, which was the best CNF concentration achieved in this study, and 115.8% higher than that (1.46 g/L) obtained from the control strain. Genome sequence data and KxyMBEL1810 generated in this study should be useful resources for metabolic engineering of K. xylinus for the enhanced CNF production.
Complete genome sequence and a genome‐scale metabolic model (GEM) of Komagataeibacter xylinus DSM 2325 were generated in this study. K. xylinus has long been studied as a model organism that produces bacterial cellulose nanofiber (CNF) having excellent physical properties for a wide range of applications. The two resources, both the genome data and GEM, should be useful for further in‐depth studies and engineering of K. xylinus DSM 2325 and other relevant strains for the enhanced CNF production.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
This paper presents study of design characteristics with wide constant power speed range (CPSR) for electric vehicle Propulsion. Through analysis of interior permanent magnet synchronous motor ...(IPMSM) control logic, design characteristic of extending CPSR is proposed. To achieve wide CPSR, center of voltage limit ellipse should be placed at cross point of current limit circle and d-axis. To analyze characteristic of voltage ellipse, four types of representative IPMSM rotor topologies are selected. Through rotor topology analysis, tendency of φ f and L ds parameters which decide center of voltage limit ellipse is analyzed. This paper also considers shifting of voltage limit ellipse center according to change in motor speed. Reflecting the result, this paper focuses on center of voltage limit ellipse position at maximum speed, because central coordinates of high-speed range determine characteristics of CPSR. Through the analysis result, this paper suggests direction of IPMSM design for wide CPSR.
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•A method to fabricate continuous hydrophobic/oleophilic RGO/ZIF-8 nanocoating on polymeric foam.•Selective oil absorption with an absorption capacity of 15–35 g/g depending on the ...viscosity of organic solvents.•Ultrafast hexane flux up to 800,000 Lm−2 h−1 and no water flux during vacuum filtration.•Universal method to fabricate metal-organic frameworks on polymeric foam.
Continuous ZIF-8/reduced graphene oxide (RGO) nanocoating is fabricated by growing ZIF-8 on RGO-coated polyurethane (PU) foam. Surface modification of PU foam can be easily achieved by immersing the PU foam in GO solution, followed by mild thermal treatment to turn the GO layer into RGO layer. Adhesion between polymer foam and ZIF-8 layer was enhanced by the inserted RGO layer because oxygen-containing groups of RGO could interact with Zn2+ precursor of ZIF-8 localizing the layer growth preferentially on the surface of RGO. The synergetic hydrophobic/oleophilic properties of RGO and ZIF-8 enable selective oil absorption of PU foam with an absorption capacity of 15–35 g/g depending on the viscosity of organic solvents. Most of all, the ZIF-8/RGO coated PU foam can filter organic solvent selectively via vacuum filtration, showing ultrafast hexane flux up to 800,000 Lm−2 h−1 and no water flux.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The learning and inference efficiencies of an artificial neural network represented by a cross‐point synaptic memristor array can be achieved using a selector, with high selectivity (Ion/Ioff) and ...sufficient death region, stacked vertically on a synaptic memristor. This can prevent a sneak current in the memristor array. A selector with multiple jar‐shaped conductive Cu filaments in the resistive switching layer is precisely fabricated by designing the Cu ion concentration depth profile of the CuGeSe layer as a filament source, TiN diffusion barrier layer, and Ge3Se7 switching layer. The selector performs super‐linear‐threshold‐switching with a selectivity of > 107, death region of −0.70–0.65 V, holding time of 300 ns, switching speed of 25 ns, and endurance cycle of > 106. In addition, the mechanism of switching is proven by the formation of conductive Cu filaments between the CuGeSe and Ge3Se7 layers under a positive bias on the top Pt electrode and an automatic rupture of the filaments after the holding time. Particularly, a spiking deep neural network using the designed one‐selector‐one‐memory cross‐point array improves the Modified National Institute of Standards and Technology classification accuracy by ≈3.8% by eliminating the sneak current in the cross‐point array during the inference process.
An artificial neural network consisting of a hardware‐based cross‐point synaptic memristor array should employ selectors with two‐terminal electrodes to prevent an undesired sneak current and to improve learning and inference efficiencies. Here, a highly reliable super‐linear‐threshold‐switching selector with multiple jar‐shaped Cu‐filaments in the amorphous Ge3Se7 resistive switching layer by controlling the Cu ion concentration depth profile is developed.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
A perovskite LED with a perovskite film treated under optimum thermal annealing conditions exhibits a significantly enhanced long‐term stability with full coverage of the green electroluminescence ...emission due to the highly uniform morphology of the perovskite film.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
A compact self-powered solar-blind UV-C photodiode was demonstrated using an ultra-wide bandgap (UWBG) α-Ga2O3 thin film as a wavelength-selective absorber layer. The UWBG-based Schottky junction ...architecture renders the use of low-performance and bulky solar-blind UV bandpass filters unnecessary. High-quality α-Ga2O3 thin films with a thickness of 1.25 µm were grown on a (0001) sapphire substrate via the halide vapor-phase epitaxy technique. The self-powered solar-blind UV-C photodetector based on the Ni/α-Ga2O3 Schottky junction exhibited excellent responsivity (1.17 × 10−4 A/W), photo-to-dark current ratio (1.12 × 105), and reproducibility, as well as fast rise/decay characteristics without persistent photoconductivity upon exposure to UV-C radiation (254 nm wavelength). The relationship between light intensity (I) and photocurrent (P) was modeled by I ∼ P0.69, indicating the high-quality of the halide vapor-phase epitaxy-grown α-Ga2O3 thin film. Upon exposure to natural sunlight, the fabricated solar-blind photodetector showed excellent solar blindness with sensitivity to UV-C radiation and did not require an external power source. Therefore, this UWBG α-Ga2O3 thin-film Schottky barrier photodiode is expected to facilitate the development of a compact and energy-independent next-generation UV-C photodetector with solar blindness.
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