Abstract
Ectoine, a compatible solute synthesized by many halophiles for hypersalinity resistance, has been successfully produced by metabolically engineered
Halomonas bluephagenesis
, which is a ...bioplastic poly(3-hydroxybutyrate) producer allowing open unsterile and continuous conditions. Here we report a de novo synthesis pathway for ectoine constructed into the chromosome of
H. bluephagenesis
utilizing two inducible systems, which serve to fine-tune the transcription levels of three clusters related to ectoine synthesis, including
ectABC
,
lysC
and
asd
based on a GFP-mediated transcriptional tuning approach. Combined with bypasses deletion, the resulting recombinant
H. bluephagenesis
TD-ADEL-58 is able to produce 28 g L
−1
ectoine during a 28 h fed-batch growth process. Co-production of ectoine and PHB is achieved to 8 g L
−1
ectoine and 32 g L
−1
dry cell mass containing 75% PHB after a 44 h growth.
H. bluephagenesis
demonstrates to be a suitable co-production chassis for polyhydroxyalkanoates and non-polymer chemicals such as ectoine.
Skeletal muscles are natural motors executing sophisticated work through precise control of linear contraction. Although various liquid crystal polymers based artificial muscles have been designed, ...the mechanism based on mainly the order–disorder transition usually leads to discrete shape morphing, leaving arbitrary and precise deformation a huge challenge. Here, one novel photoresponsive hemiphasmidic side‐chain liquid crystal polymer with a unique “breathing” columnar phase that enables continuous morphing is presented. Due to confinement inside the supramolecular columnar assembly, the cooperative movements of side‐chains and backbones generate a significant negative thermal expansion and lead to temperature‐controllable muscle‐like elongation/contraction in the oriented polymer strip. The irreversible isomerization of the photoresponsive mesogens results in the synergistic phototunable bending and high‐contrast fluorescence change. Based on the orthogonal responses to heat and light, controllable arm‐like bending motions of this material, which is applicable in constructing advanced artificial muscles or intelligent soft robotics, are further demonstrated.
A hemiphasmidic side‐chain liquid crystal polymer forms multichain supramolecular columnar assemblies. Through the cooperative movements of main‐chains and side‐chains, the uniaxially aligned polymer strip executes muscle‐like continuous and reversible elongation/contraction. The irreversible photoisomerization of mesogens further endows the polymer strip with arm‐like phototunable bending which can lift heavy load. Both deformations are under precise control of temperature.
A control strategy of islanded microgrid is proposed in this paper against the harmonic circulation of the inverters and the Point of Common Coupling (PCC) voltage harmonic distortion of the ...microgrid caused by nonlinear load. The reference voltage of the inverter's outer voltage loop is given by the decoupling control of the fundamental and harmonic components. Virtual synchronous generator (VSG) is adopted in fundamental domain. In harmonic domain, adaptive harmonic compensation and harmonic virtual impedance are applied to obtain the harmonic components of the reference voltage of the outer voltage loop. The hybrid control strategy combining P control and repetitive control in parallel is adopted in the outer voltage loop. Multi-period repetitive control (MPRC) with fast repetitive control (FRC) is adopted to improve the tracking control performance of the main harmonic components of the given reference voltage. Fractional order delay approximated by Lagrange interpolation polynomial FIR filter is applied in MPRC for different repetitive control periods at the fixed sampling period. The output harmonic current of the inverters can be distributed autonomously according to the capacity of the inverters to suppress the harmonic circulation, and the suppression of the PCC voltage harmonic distortion is realized. Simulation based on Matlab/Simulink and hardware-in-loop(HIL) test are carried out, and the results show that the proposed control strategy is effective.
Clustered regularly interspaced short palindromic repeats interference (CRISPRi) has provided an efficient approach for targeted gene inhibition. A non-model microorganism Halomonas species TD01 has ...been developed as a promising industrial producer of polyhydroxyalkanoates (PHA), a family of biodegradable polyesters accumulated by bacteria as a carbon and energy reserve compound. A controllable gene repression system, such as CRISPRi, is needed for Halomonas sp. TD01 to regulate its gene expression levels.
For the first time CRISPRi was successfully used in Halomonas sp. TD01 to repress expression of ftsZ gene encoding bacterial fission ring formation protein, leading to an elongated cell morphology with typical filamentous shape similar to phenomenon observed with Escherichia coli. CRISPRi was employed to regulate expressions of prpC gene encoding 2-methylcitrate synthase for regulating 3-hydroxyvalerate monomer ratio in PHBV copolymers of 3-hydroxybutyrate (HB) and 3-hydroxyvalerate (HV). Percentages of HV in PHBV copolymers were controllable ranging from less than 1 to 13%. Furthermore, repressions on gltA gene encoding citrate synthase channeled more acetyl-CoA from the tricarboxylic acid (TCA) cycle to poly(3-hydroxybutyrate) (PHB) synthesis. The PHB accumulation by Halomonas sp. TD01 with its gltA gene repressed in various intensities via CRISPRi was increased by approximately 8% compared with the wild type control containing the CRISPRi vector without target.
It has now been confirmed that the CRISPRi system can be applied to Halomonas sp. TD01, a promising industrial strain for production of various PHA and chemicals under open and continuous fermentation process conditions. In details, the CRISPRi system was successfully designed in this study to target genes of ftsZ, prpC and gltA, achieving longer cell sizes, channeling more substrates to PHBV and PHB synthesis, respectively. CRISPRi can be expected to use for more metabolic engineering applications in non-model organisms.
•The separate S-N curves are firstly detected in additively manufactured metals.•Fatigue cracks originate from gas pores, lack of fusions, and columnar grains.•ΔK at the border of rough area ...corresponds to propagation threshold for long cracks.•Fatigue sensitivity of maximal micro-crack type, size, and location increase successively.
Ultrasonic fatigue tests were performed to investigate high and very high cycle fatigue behaviors of a laser additively manufactured Inconel 718 (IN718) alloy in the as-deposited condition. The results indicate that the competition failure behavior between the surface and interior crack initiation results in the separate S-N curve. Both manufacturing defects (e.g., gas pore, lack of fusion) and columnar grains (matrix) observed in the microstructure could act as the original fatigue micro-cracks due to the effective restriction on manufacturing defects. The fatigue sensitivity levels increase successively in terms of the type, size, and location of the maximal micro-crack.
3-Hydroxypropionic acid (3HP), an important three carbon (C3) chemical, is designated as one of the top platform chemicals with an urgent need for improved industrial production. Halomonas ...bluephagenesis shows the potential as a chassis for competitive bioproduction of various chemicals due to its ability to grow under an open, unsterile and continuous process. Here, we report the strategy for producing 3HP and its copolymer poly(3-hydroxybutyrate-co-3-hydroxypropionate) (P3HB3HP) by the development of H. bluephagenesis. The transcriptome analysis reveals its 3HP degradation and synthesis pathways involving endogenous synthetic enzymes from 1,3-propanediol. Combing the optimized expression of aldehyde dehydrogenase (AldD
), an engineered H. bluephagenesis strain of whose 3HP degradation pathway is deleted and that overexpresses alcohol dehydrogenases (AdhP) on its genome under a balanced redox state, is constructed with an enhanced 1.3-propanediol-dependent 3HP biosynthetic pathway to produce 154 g L
of 3HP with a yield and productivity of 0.93 g g
1,3-propanediol and 2.4 g L
h
, respectively. Moreover, the strain could also accumulate 60% poly(3-hydroxybutyrate-co-32-45% 3-hydroxypropionate) in the dry cell mass, demonstrating to be a suitable chassis for hyperproduction of 3HP and P3HB3HP.
Ten eleven translocation (TET) enzymes, including TET1, TET2 and TET3, convert 5-methylcytosine to 5-hydroxymethylcytosine and regulate gene transcription. However, the molecular mechanism by which ...TET family enzymes regulate gene transcription remains elusive. Using protein affinity purification, here we search for functional partners of TET proteins, and find that TET2 and TET3 associate with O-linked β-N-acetylglucosamine (O-GlcNAc) transferase (OGT), an enzyme that by itself catalyses the addition of O-GlcNAc onto serine and threonine residues (O-GlcNAcylation) in vivo. TET2 directly interacts with OGT, which is important for the chromatin association of OGT in vivo. Although this specific interaction does not regulate the enzymatic activity of TET2, it facilitates OGT-dependent histone O-GlcNAcylation. Moreover, OGT associates with TET2 at transcription start sites. Downregulation of TET2 reduces the amount of histone 2B Ser 112 GlcNAc marks in vivo, which are associated with gene transcription regulation. Taken together, these results reveal a TET2-dependent O-GlcNAcylation of chromatin. The double epigenetic modifications on both DNA and histones by TET2 and OGT coordinate together for the regulation of gene transcription.
A new type of physically linked double‐network hydrogel is synthesized by a simple, time‐saving, facile, easily controlled, one‐pot method. The resulting agar/polyacrylamide double‐network hydrogels ...exhibit good mechanical properties, excellent recoverability, and a unique free‐shapeable property, which makes them very promising hydrogels for load‐bearing soft tissues.
Cytotoxic potential of silver nanoparticles Zhang, Tianlu; Wang, Liming; Chen, Qiang ...
Yonsei Medical Journal/Yonsei medical journal,
03/2014, Volume:
55, Issue:
2
Journal Article
Peer reviewed
Open access
Silver nanoparticles (AgNPs) have been widely used in industrial, household, and healthcare-related products due to their excellent antimicrobial activity. With increased exposure of AgNPs to human ...beings, the risk of safety has attracted much attention from the public and scientists. In review of recent studies, we discuss the potential impact of AgNPs on individuals at the cell level. In detail, we highlight the main effects mediated by AgNPs on the cell, such as cell uptake and intracellular distribution, cytotoxicity, genotoxicity, and immunological responses, as well as some of the major factors that influence these effects in vitro and in vivo, such as dose, time, size, shape, surface chemistry, and cell type. At the end, we summarize the main influences on the cell and indicate the challenges in this field, which may be helpful for assessing the risk of AgNPs in future.
Manipulation bacterial cells for maximizing PHA synthesis.▪
•Improvements on PHA biosynthesis must be considered in a systematic way.•Directing metabolic flux to PHA synthesis is critical for ...improving conversion rate.•Engineering rapid growth and cell sizes are important for PHA biosynthesis efficiency.•The newly emerging tools and reprogramming DNA are helping to control PHA biosynthesis.•A suitable chassis for engineering all the above properties is desirable.
Biosynthesis of polyhydroxyalkanoates (PHA) has been studied since the 1920s. The biosynthesis pathways have been well understood and various attempts have been made to improve the PHA biosynthesis efficiency. Recent progresses have been focused on systematic improvements on PHA biosynthesis including changing growth pattern for rapid proliferation, engineering to enlarge cell sizes for more PHA accumulation space, reprogramming the PHA synthesis pathways using optimized RBS and promoter, redirecting metabolic flux to PHA synthesis using CRISPR/Cas9 tools, and very importantly, the employment of non-traditional host such as halophiles for reduced complexity on PHA production. All of the efforts should lead to ultrahigh PHA accumulation, controllable PHA compositions and molecular weights, open and continuous PHA production with gravity separation processes, resulting in competitive PHA production cost.
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