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1.
Appl Opt ; 63(10): A59-A69, 2024 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-38568512

RESUMO

Based on the generalized Lorenz-Mie theory (GLMT) and the scattering theory of uniaxial spheres, a theoretical approach is introduced to study the axial radiation force (AOF) exerted on a uniaxial anisotropic sphere illuminated by an on-axis high-order Bessel (vortex) beams (HOBVBs). Applying Maxwell's stress tensor, an analytical expression of the AOF on a uniaxial anisotropic sphere by the on-axis HOBVB is derived. The correctness of the theoretical and numerical results is verified by comparing the AOF on an isotropic sphere by a zero-order Bessel beam (ZOBB) with those results by a plane wave, Gaussian beam, and ZOBB. The focus of this study is to determine some conditions of the tractor beam, so as to realize the inverse motion of an anisotropic sphere through a Bessel beam. The range of optical pulling force (OPF) that can pull particles in reverse motion generated by zero-order and first-order Bessel beams is extended from isotropic spherical particles to anisotropic spherical particles. The effects of the sphere radius, conical angle, and especially electromagnetic anisotropy parameters on the OPF in water or a vacuum environment are discussed in detail. Moreover, the OPF exerted on the uniaxial anisotropic sphere illuminated by a HOBVB with l=2, 3, and 4 is also exhibited. It indicates that the HOBVB with l=2, 3 is also a good tractor beam for the uniaxial anisotropic sphere. The OPF generated by Bessel beams on uniaxial anisotropic spherical particles is not only affected by the conical angle and radius but is also significantly influenced by anisotropic parameters and topological charges. These properties of the OPF are different from those on an isotropic sphere. The theory and results are hopeful to provide an effective theoretical basis for the study of optical micromanipulation of biological and anisotropic complex particles by optical tractor (vortex) beams.

2.
Int J Biol Macromol ; 261(Pt 2): 129838, 2024 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-38307428

RESUMO

A novel α-amylase Amy03713 was screened and cloned from the starch utilization strain Vibrio alginolyticus LHF01. When heterologously expressed in Escherichia coli, Amy03713 exhibited the highest enzyme activity at 45 °C and pH 7, maintained >50 % of the enzyme activity in the range of 25-75 °C and pH 5-9, and sustained >80 % of the enzyme activity in 25 % (w/v) of NaCl solution, thus showing a wide range of adapted temperatures, pH, and salt concentrations. Halomonas bluephagenesis harboring amy03713 gene was able to directly utilize starch. With optimized amylase expression, H. bluephagenesis could produce poly(3-hydroxybutyrate) (PHB), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), and poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P34HB). When cultured for PHB production, recombinant H. bluephagenesis was able to grow up to a cell dry weight of 11.26 g/L, achieving a PHB titer of 6.32 g/L, which is the highest titer that has been reported for PHB production from starch in shake flasks. This study suggests that Amy03713 is an ideal amylase for PHA production using starch as the carbon source in H. bluephagenesis.


Assuntos
Halomonas , Ácidos Pentanoicos , Poli-Hidroxialcanoatos , Halomonas/genética , Halomonas/metabolismo , Carbono/metabolismo , Amido/metabolismo , Hidroxibutiratos/metabolismo , alfa-Amilases/genética , alfa-Amilases/metabolismo , Poliésteres/metabolismo
3.
J Opt Soc Am A Opt Image Sci Vis ; 40(3): 510-520, 2023 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-37133025

RESUMO

Analytical solutions to the scattering of a uniform uniaxial anisotropic sphere illuminated by an on-axis high-order Bessel vortex beam (HOBVB) are investigated. Using the vector wave theory, the expansion coefficients of the incident HOBVB in terms of the spherical vector wave functions (SVWFs) are obtained. According to the orthogonality of the associated Legendre function and exponential function, more concise expressions of the expansion coefficients are derived. It can reinterpret the incident HOBVB faster compared with the expansion coefficients of double integral forms. The internal fields of a uniform uniaxial anisotropic sphere are proposed in the integrating form of the SVWFs by introducing the Fourier transform. The differences of scattering characteristics of a uniaxial anisotropic sphere illuminated by a zero-order Bessel beam, Gaussian beam, and HOBVB are exhibited. Influences of the topological charge, conical angle, and particle size parameters on the angle distributions of the radar cross section are analyzed in detail. The scattering and extinction efficiencies varied with the particle radius, conical angle, permeability, and dielectric anisotropy are also discussed. The results provide insights into the scattering and light-matter interactions and may find important applications in optical propagation and optical micromanipulation of biological and anisotropic complex particles.

4.
Chin J Integr Med ; 29(6): 556-565, 2023 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-37052766

RESUMO

Postoperative adhesion (PA) is currently one of the most unpleasant complications following surgical procedures. Researchers have developed several new strategies to alleviate the formation of PA to a great extent, but so far, no single measure or treatment can meet the expectations and requirements of clinical patients needing complete PA prevention. Chinese medicine (CM) has been widely used for thousands of years based on its remarkable efficacy and indispensable advantages CM treatments are gradually being accepted by modern medicine. Therefore, this review summarizes the formating process of PA and the efficacy and action mechanism of CM treatments, including their pharmacological effects, therapeutic mechanisms and advantages in PA prevention. We aim to improve the understanding of clinicians and researchers on CM prevention in the development of PA and promote the in-depth development and industrialization process of related drugs.


Assuntos
Medicamentos de Ervas Chinesas , Medicina Tradicional Chinesa , Humanos , Aderências Teciduais/tratamento farmacológico , Aderências Teciduais/prevenção & controle , Desenvolvimento Industrial , Medicamentos de Ervas Chinesas/farmacologia , Medicamentos de Ervas Chinesas/uso terapêutico
5.
Synth Syst Biotechnol ; 8(2): 235-241, 2023 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-36970069

RESUMO

Fumarate is a value-added chemical that is widely used in food, medicine, material, and agriculture industries. With the rising attention to the demand for fumarate and sustainable development, many novel alternative ways that can replace the traditional petrochemical routes emerged. The in vitro cell-free multi-enzyme catalysis is an effective method to produce high value chemicals. In this study, a multi-enzyme catalytic pathway comprising three enzymes for fumarate production from low-cost substrates acetate and glyoxylate was designed. The acetyl-CoA synthase, malate synthase, and fumarase from Escherichia coli were selected and the coenzyme A achieved recyclable. The enzymatic properties and optimization of reaction system were investigated, reaching a fumarate yield of 0.34 mM with a conversion rate of 34% after 20 h of reaction. We proposed and realized the conversion of acetate and glyoxylate to fumarate in vitro using a cell-free multi-enzyme catalytic system, thus providing an alternative approach for the production of fumarate.

6.
Front Bioeng Biotechnol ; 11: 1130368, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-36824353

RESUMO

Vibrio alginolyticus LHF01 was engineered to efficiently produce poly-3-hydroxybutyrate (PHB) from starch in this study. Firstly, the ability of Vibrio alginolyticus LHF01 to directly accumulate PHB using soluble starch as the carbon source was explored, and the highest PHB titer of 2.06 g/L was obtained in 18 h shake flask cultivation. Then, with the analysis of genomic information of V. alginolyticus LHF01, the PHB synthesis operon and amylase genes were identified. Subsequently, the effects of overexpressing PHB synthesis operon and amylase on PHB production were studied. Especially, with the co-expression of PHB synthesis operon and amylase, the starch consumption rate was improved and the PHB titer was more than doubled. The addition of 20 g/L insoluble corn starch could be exhausted in 6-7 h cultivation, and the PHB titer was 4.32 g/L. To the best of our knowledge, V. alginolyticus was firstly engineered to produce PHB with the direct utilization of starch, and this stain can be considered as a novel host to produce PHB using starch as the raw material.

7.
World J Clin Cases ; 10(31): 11442-11453, 2022 Nov 06.
Artigo em Inglês | MEDLINE | ID: mdl-36387811

RESUMO

BACKGROUND: It remains unclear whether video aids can improve the quality of bystander cardiopulmonary resuscitation (CPR). AIM: To summarize simulation-based studies aiming at improving bystander CPR associated with the quality of chest compression and time-related quality parameters. METHODS: The systematic review was conducted according to the PRISMA guidelines. All relevant studies were searched through PubMed, EMBASE, Medline and Cochrane Library databases. The risk of bias was evaluated using the Cochrane collaboration tool. RESULTS: A total of 259 studies were eligible for inclusion, and 6 randomised controlled trial studies were ultimately included. The results of meta-analysis indicated that video-assisted CPR (V-CPR) was significantly associated with the improved mean chest compression rate [OR = 0.66 (0.49-0.82), P < 0.001], and the proportion of chest compression with correct hand positioning [OR = 1.63 (0.71-2.55), P < 0.001]. However, the difference in mean chest compression depth was not statistically significant [OR = 0.18 (-0.07-0.42), P = 0.15], and V-CPR was not associated with the time to first chest compression compared to telecommunicator CPR [OR = -0.12 (-0.88-0.63), P = 0.75]. CONCLUSION: Video real-time guidance by the dispatcher can improve the quality of bystander CPR to a certain extent. However, the quality is still not ideal, and there is a lack of guidance caused by poor video signal or inadequate interaction.

8.
Int J Biol Macromol ; 221: 1365-1372, 2022 Nov 30.
Artigo em Inglês | MEDLINE | ID: mdl-36126806

RESUMO

Volatile fatty acids (VFAs) derived from biomass are considered to be economical and environmentally friendly feedstocks for microbial fermentation. Converting VFAs to polyhydroxyalkanoate (PHA) could reduce the substrate cost and provide an economically viable route for the commercialization of PHA. The halophilic bacteria Salinivibrio spp. TGB4 and TGB19, newly isolated from salt fields, were found to accumulate poly-3-hydroxybutyrate (PHB) using acetate or butyrate as the substrate. Both strains exhibited considerable cell growth (OD600 of ~8) even at acetate concentration of 100 g/L. In shake flask cultures, TGB4 produced PHB titers of 0.90 and 1.34 g/L, while TGB19 produced PHB titers of 0.25 and 2.53 g/L with acetate and butyrate, respectively. When acetate and butyrate were both applied, PHB production was significantly increased, and the PHB titer of TGB4 and TGB19 reached 6.14 and 6.84 g/L, respectively. After optimizing the culture medium, TGB19 produced 8.42 g/L PHB, corresponding to 88.55 wt% of cell dry weight. During fed-batch cultivation, TGB19 produced a PHB titer of 53.23 g/L. This is the highest reported PHB titer using acetate and butyrate by pure microbial cultures and would provide promising hosts for the industrial production of PHA from VFAs.


Assuntos
Poli-Hidroxialcanoatos , Vibrionaceae , Butiratos , Hidroxibutiratos , Poliésteres/metabolismo , Ácidos Graxos Voláteis , Acetatos , Vibrionaceae/metabolismo , Fermentação
9.
Int J Biol Macromol ; 195: 255-263, 2022 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-34914906

RESUMO

Several species of novel marine bacteria from the genus Marinobacterium, including M. nitratireducens, M. sediminicola, and M. zhoushanense were found to be capable of producing polyhydroxyalkanoates (PHA) using sugars and volatile fatty acids (VFAs) as the carbon source. M. zhoushanense produced poly-3-hydroxybutytate (PHB) from sucrose, achieving a product titer and PHB content of 2.89 g/L and 64.05 wt%, respectively. By contrast, M. nitratireducens accumulated 3.38 g/L PHB and 66.80 wt% polymer content using butyrate as the substrate. A third species, M. sediminicola showed favorable tolerance to propionate, butyrate, and valerate. The use of 10 g/L valerate yielded 3.37 g/L poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), with a 3-hydroxyvalerate (3 HV) monomer content of 94.75 mol%. Moreover, M. sediminicola could be manipulated to produce PHBV with changeable polymer compositions by feeding different mixtures of VFAs. Our results indicate that M. sediminicola is a promising halophilic bacterium for the production of PHA.


Assuntos
Ácido 3-Hidroxibutírico/biossíntese , Oceanospirillaceae/metabolismo , Poli-Hidroxialcanoatos/biossíntese , Ácido 3-Hidroxibutírico/metabolismo , Butiratos , Carbono , Ácidos Graxos Voláteis/metabolismo , Hidroxibutiratos , Poliésteres/química , Poli-Hidroxialcanoatos/metabolismo , Propionatos , Açúcares/metabolismo , Valeratos
10.
Molecules ; 26(20)2021 Oct 17.
Artigo em Inglês | MEDLINE | ID: mdl-34684864

RESUMO

Vibrio alginolyticus is a halophilic organism usually found in marine environments. It has attracted attention as an opportunistic pathogen of aquatic animals and humans, but there are very few reports on polyhydroxyalkanoate (PHA) production using V. alginolyticus as the host. In this study, two V. alginolyticus strains, LHF01 and LHF02, isolated from water samples collected from salt fields were found to produce poly(3-hydroxybutyrate) (PHB) from a variety of sugars and organic acids. Glycerol was the best carbon source and yielded the highest PHB titer in both strains. Further optimization of the NaCl concentration and culture temperature improved the PHB titer from 1.87 to 5.08 g/L in V. alginolyticus LHF01. In addition, the use of propionate as a secondary carbon source resulted in the production of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV). V. alginolyticus LHF01 may be a promising host for PHA production using cheap waste glycerol from biodiesel refining.


Assuntos
Poli-Hidroxialcanoatos/biossíntese , Vibrio alginolyticus/metabolismo , Carbono/metabolismo , China , Fermentação , Proibitinas , Águas Salinas , Vibrio alginolyticus/isolamento & purificação , Vibrio alginolyticus/ultraestrutura
11.
Int J Biol Macromol ; 186: 574-579, 2021 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-34245739

RESUMO

A moderately halophilic bacterium isolated from the water samples collected from a salt field, Salinivibrio sp. TGB10 was found capable of producing poly-3-hydroxybutytate (PHB) from various sugars. Cell dry weight (CDW) of 8.82 g/L and PHB titer of 6.84 g/L were obtained using glucose as the carbon source after 24 h of cultivation in shake flasks. Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) was synthesized when propionate was provided as secondary carbon source. Salinivibrio sp. TGB10 exhibited favorable tolerance to propionate. The use of 8 g/L propionate and 20 g/L glucose as combinational substrates yielded 1.45 g/L PHBV with a 3-hydroxyvalerate monomer content of 72.02 mol% in flask cultures. In bioreactor study, CDW of 33.45 g/L and PHBV titer of 27.36 g/L were obtained after 108 h of fed-batch cultivation. The results indicated that Salinivibrio sp. TGB10 is a promising halophilic bacterium for the production of PHBV with various polymer compositions.


Assuntos
Hidroxibutiratos/metabolismo , Poliésteres/metabolismo , Poli-Hidroxialcanoatos/metabolismo , Vibrionaceae/enzimologia , Reatores Biológicos , Ácidos Graxos Voláteis/metabolismo , Fermentação , Especificidade por Substrato , Açúcares/metabolismo , Vibrionaceae/crescimento & desenvolvimento , Microbiologia da Água
12.
J Opt Soc Am A Opt Image Sci Vis ; 38(5): 616-627, 2021 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-33983266

RESUMO

Based on Maxwell's stress tensor and the generalized Lorenz-Mie theory, a theoretical approach is introduced to study the radiation force exerted on a uniaxial anisotropic sphere illuminated by dual counter-propagating (CP) Gaussian beams. The beams propagate with arbitrary direction and are expanded in terms of the spherical vector wave functions (SVWFs) in a particle coordinate system using the coordinate rotation theorem of the SVWFs. The total expansion coefficients of the incident fields are derived by superposition of the vector fields. Using Maxwell stress tensor analysis, the analytical expressions of the radiation force on a homogeneous absorbing uniaxial anisotropic sphere are obtained. The accuracy of the theory is verified by comparing the radiation forces of the anisotropic sphere reduced to the special cases of an isotropic sphere. In order to study the equilibrium state, the effects of beam parameters, particle size parameters, and anisotropy parameters on the radiation force are discussed in detail. Compared with the isotropic particle, the equilibrium status is sensitive to the anisotropic parameters. Moreover, the properties of optical force on a uniaxial anisotropic sphere in a single Gaussian beam trap and Gaussian standing wave trap are compared. It indicates that the CP Gaussian beam trap may more easily capture or confine the anisotropic particle. However, the radiation force exerted on an anisotropic sphere exhibits very different properties when the beams do not propagate along the primary optical axis. The influence of the anisotropic parameter on the radiation force by CP Gaussian beams is different from that of a single Gaussian beam. In summary, even for anisotropic particles, the Gaussian standing wave trap also exhibits significant advantages when compared with the single Gaussian beam trap. The theoretical predictions of radiation forces exerted on a uniaxial anisotropic sphere by dual Gaussian beams provide effective ways to achieve the improvement of optical tweezers as well as the capture, suspension, and high-precision delivery of anisotropic particles.

13.
Mar Genomics ; 53: 100754, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32883436

RESUMO

The marine bacterium Neptunomonas concharum was firstly characterized in 2012. It preferred to utilize acetate as the carbon source to accumulate poly-3-hydroxybutyrate (PHB) as intracellular carbon and energy storage. Here we report the genomic characteristics of N. concharum JCM17730T. The complete genome sequence of N. concharum JCM17730T consists of 3,561,992 bp in one contig, without plasmid. Analysis of coding sequences revealed the presence of genomic features involved in acetate assimilation and PHB metabolism. The genome of N. concharum JCM17730T contains three genes encoding acetyl-CoA synthetase and two genes encoding isocitrate lyase. Three polyhydroxyalkanoate synthases and one polyhydroxyalkanoate depolymerase are scattered throughout the genomic DNA. The genome features provide interesting insights into the acetate and PHB metabolism of N. concharum JCM17730T and would facilitate further research on the genetic engineering of marine bacteria for efficient PHB production.


Assuntos
Arcidae/microbiologia , Genoma Bacteriano , Oceanospirillaceae/genética , Acetatos/metabolismo , Animais , República da Coreia , Sequenciamento Completo do Genoma
14.
J Biotechnol ; 319: 69-73, 2020 Aug 10.
Artigo em Inglês | MEDLINE | ID: mdl-32526261

RESUMO

Neptunomonas concharum JCM17730 was isolated from an ark clam sample and characterized as a mesophilic bacterium. The genome of N. concharum JCM17730 contains thirteen genes related to polyhydroxyalkanoates (PHA) metabolism. Three PHA synthase encoding genes were identified, and phylogenetic analysis of enzyme sequences suggested the presence of two class I PHA synthases and one class III PHA synthase. The PHA synthases of N. concharum were heterologously expressed with acetyl-CoA acetyltransferase and acetoacetyl-CoA reductase in Escherichia coli to confirm the catalytic activity of each PHA synthase. Recombinants harboring different PHA synthase exhibit important distinctions in poly-3-hydroxybutyrate synthesis ability under various temperatures. Decreased cultivation temperature (≤30 °C) significantly improved PHB titer and content. This is the first report on characterization of PHA synthases from the marine genus Neptunomonas and would provide molecular basis for PHA production using Neptunomonas species.


Assuntos
Aciltransferases , Proteínas de Bactérias , Oceanospirillaceae , Aciltransferases/química , Aciltransferases/genética , Aciltransferases/metabolismo , Organismos Aquáticos/enzimologia , Organismos Aquáticos/genética , Proteínas de Bactérias/química , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Escherichia coli/genética , Escherichia coli/metabolismo , Oceanospirillaceae/enzimologia , Oceanospirillaceae/genética , Poli-Hidroxialcanoatos/metabolismo , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo
15.
J Biosci Bioeng ; 130(3): 290-294, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32482608

RESUMO

Aeromonas hydrophila 4AK4 normally produces the copolymer of 3-hydroxybutyrate and 3-hydroxyhexanoate (PHBHHx) using lauric acid as the carbon source. In this study we reported the metabolic engineering of A. hydrophila 4AK4 for the production of polyhydroxyalkanoate (PHA) using acetate as a main carbon source. Recombinant A. hydrophila overexpressing ß-ketothiolase and acetoacetyl-CoA reductase could accumulate poly-3-hydroxybutyrate (PHB) from acetate with a polymer content of 1.39 wt%. Further overexpression of acetate kinase/phosphotransacetylase and acetyl-CoA synthetase improved PHB content to 8.75 wt% and 19.82 wt%, respectively. When acetate and propionate were simultaneously supplied as carbon sources, the engineered A. hydrophila overexpressing ß-ketothiolase, acetoacetyl-CoA reductase, and acetyl-CoA synthetase was found able to produce the copolymer of 3-hydroxybutyrate and 3-hydroxyvalerate (PHBV). The recombinant grew to 3.79 g/L cell dry weight (CDW) containing 15.02 wt% PHBV. Our proposed metabolic engineering strategies illustrate the feasibility for producing PHA from acetate by A. hydrophila.


Assuntos
Acetatos/metabolismo , Aeromonas hydrophila/genética , Aeromonas hydrophila/metabolismo , Engenharia Metabólica , Poli-Hidroxialcanoatos/biossíntese , Ácido 3-Hidroxibutírico/metabolismo , Acetil-CoA C-Aciltransferase/genética , Oxirredutases do Álcool/genética , Ácidos Pentanoicos/metabolismo
16.
World J Psychiatry ; 10(12): 286-298, 2020 Dec 19.
Artigo em Inglês | MEDLINE | ID: mdl-33392005

RESUMO

BACKGROUND: Post-traumatic stress disorder (PTSD) is a serious stress-related disorder. AIM: To identify the key genes and pathways to uncover the potential mechanisms of PTSD using bioinformatics methods. METHODS: Gene expression profiles were obtained from the Gene Expression Omnibus database. The differentially expressed genes (DEGs) were identified by using GEO2R. Gene functional annotation and pathway enrichment were then conducted. The gene-pathway network was constructed with Cytoscape software. Quantitative real-time polymerase chain reaction (qRT-PCR) analysis was applied for validation, and text mining by Coremine Medical was used to confirm the connections among genes and pathways. RESULTS: We identified 973 DEGs including 358 upregulated genes and 615 downregulated genes in PTSD. A group of centrality hub genes and significantly enriched pathways (MAPK, Ras, and ErbB signaling pathways) were identified by using gene functional assignment and enrichment analyses. Six genes (KRAS, EGFR, NFKB1, FGF12, PRKCA, and RAF1) were selected to validate using qRT-PCR. The results of text mining further confirmed the correlation among hub genes and the enriched pathways. It indicated that these altered genes displayed functional roles in PTSD via these pathways, which might serve as key signatures in the pathogenesis of PTSD. CONCLUSION: The current study identified a panel of candidate genes and important pathways, which might help us deepen our understanding of the underlying mechanism of PTSD at the molecular level. However, further studies are warranted to discover the critical regulatory mechanism of these genes via relevant pathways in PTSD.

17.
J Biotechnol ; 291: 41-45, 2019 Feb 10.
Artigo em Inglês | MEDLINE | ID: mdl-30615909

RESUMO

Escherichia coli was metabolically engineered to synthesize glycolate using acetate as the carbon source. The native glyoxylate bypass pathway was reinforced by the overexpression of isocitrate lyase and isocitrate dehydrogenase kinase/phosphatase. Glyoxylate/hydroxypyruvate reductase was overexpressed to convert glyoxylate to glycolate. Meanwhile, side reactions were eliminated by inactivating genes encoding malate synthase, glyoxylate carboligase, and glycolate oxidase to prevent loss of glyoxylate and glycolate. The engineered E. coli produced 1.78 g/L glycolate from 3.23 g/L acetate after 48 h shake flask cultivation using minimal medium supplemented with 1 g/L yeast extract. When citrate synthase, phosphotransacetylase, and acetate kinase were co-overexpressed to strengthen the tricarboxylic acid cycle and acetate utilization, glycolate production titer was improved to 2.75 g/L with pH control in shake flasks. The results of this work offer an approach for producing glycolate using acetate as the carbon source.


Assuntos
Acetatos/metabolismo , Escherichia coli/metabolismo , Glicolatos/metabolismo , Oxirredutases do Álcool/genética , Citrato (si)-Sintase/genética , Escherichia coli/genética , Isocitrato Liase/genética , Engenharia Metabólica , Proteínas Serina-Treonina Quinases/genética
18.
Microb Cell Fact ; 17(1): 102, 2018 Jul 03.
Artigo em Inglês | MEDLINE | ID: mdl-29970091

RESUMO

BACKGROUND: High production cost of bioplastics polyhydroxyalkanoates (PHA) is a major obstacle to replace traditional petro-based plastics. To address the challenges, strategies towards upstream metabolic engineering and downstream fermentation optimizations have been continuously pursued. Given that the feedstocks especially carbon sources account up to a large portion of the production cost, it is of great importance to explore low cost substrates to manufacture PHA economically. RESULTS: Escherichia coli was metabolically engineered to synthesize poly-3-hydroxybutyrate (P3HB), poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P3HB4HB), and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) using acetate as a main carbon source. Overexpression of phosphotransacetylase/acetate kinase pathway was shown to be an effective strategy for improving acetate assimilation and biopolymer production. The recombinant strain overexpressing phosphotransacetylase/acetate kinase and P3HB synthesis operon produced 1.27 g/L P3HB when grown on minimal medium supplemented with 10 g/L yeast extract and 5 g/L acetate in shake flask cultures. Further introduction succinate semialdehyde dehydrogenase, 4-hydroxybutyrate dehydrogenase, and CoA transferase lead to the accumulation of P3HB4HB, reaching a titer of 1.71 g/L with a 4-hydroxybutyrate monomer content of 5.79 mol%. When 1 g/L of α-ketoglutarate or citrate was added to the medium, P3HB4HB titer increased to 1.99 and 2.15 g/L, respectively. To achieve PHBV synthesis, acetate and propionate were simultaneously supplied and propionyl-CoA transferase was overexpressed to provide 3-hydroxyvalerate precursor. The resulting strain produced 0.33 g/L PHBV with a 3-hydroxyvalerate monomer content of 6.58 mol%. Further overexpression of propionate permease improved PHBV titer and 3-hydroxyvalerate monomer content to 1.09 g/L and 10.37 mol%, respectively. CONCLUSIONS: The application of acetate as carbon source for microbial fermentation could reduce the consumption of food and agro-based renewable bioresources for biorefineries. Our proposed metabolic engineering strategies illustrate the feasibility for producing polyhydroxyalkanoates using acetate as a main carbon source. Overall, as an abundant and renewable resource, acetate would be developed into a cost-effective feedstock to achieve low cost production of chemicals, materials, and biofuels.


Assuntos
Acetatos/metabolismo , Escherichia coli/metabolismo , Engenharia Metabólica , Poli-Hidroxialcanoatos/biossíntese , Ácido 3-Hidroxibutírico/biossíntese , Acetato Quinase/genética , Técnicas de Cultura Celular por Lotes , Biopolímeros/biossíntese , Carbono/metabolismo , Escherichia coli/genética , Fermentação , Fosfato Acetiltransferase/genética , Plásticos
19.
Metab Eng ; 48: 25-32, 2018 07.
Artigo em Inglês | MEDLINE | ID: mdl-29800611

RESUMO

Malate is regarded as one of the key building block chemicals which can potentially be produced from biomass at a large scale. Although glucose has been extensively studied as the substrate for malate production, its high price and potential competition with food production are serious limiting factors. In this study, Escherichia coli was metabolically engineered to effectively produce malate from xylose, the second most abundant sugar component of lignocellulosic biomass. First, the biosynthetic route of malate was constructed by overexpressing D-tagatose 3-epimerase, L-fuculokinase, L-fuculose-phosphate aldolase, and aldehyde dehydrogenase A. Second, genes encoding malic enzyme, malate dehydrogenase, and fumarate hydratase were knocked out to eliminate malate consumption, resulting in a titer of 1.99 g/l malate and a yield of 0.47 g malate/g xylose. Third, glycolate oxidase and malate synthase were overexpressed to strengthen the conversion of glycolate to malate, which led to a titer of 4.33 g/l malate and a yield of 0.83 g malate/g xylose, reaching 93% of the theoretical yield. Finally, catalase HPII was overexpressed to decompose H2O2 and alleviate its toxicity, which improved cell growth and further boosted malate titer to 5.90 g/l with a yield of 0.80 g malate/g xylose. To the best of our knowledge, this is the first study to report efficient malate production from xylose as the carbon source.


Assuntos
Proteínas de Escherichia coli , Escherichia coli , Malatos/metabolismo , Engenharia Metabólica , Xilose/metabolismo , Escherichia coli/enzimologia , Escherichia coli/genética , Proteínas de Escherichia coli/genética , Proteínas de Escherichia coli/metabolismo
20.
J Opt Soc Am A Opt Image Sci Vis ; 35(2): 336-345, 2018 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-29400884

RESUMO

Based on the generalized Lorentz-Mie theory (GLMT) and the localized approximation of the beam shape coefficients, we derived the expansions of incident elliptic Gaussian (EG) beams in terms of spherical vector wave functions (SVWFs). Utilizing multiple scattering (MS) equations and electromagnetic momentum (EM) theory, the lateral binding force (BF) exerted on a bi-sphere induced by an EG beam is calculated. Numerical effects of various parameters such as beam waist widths, beam polarization states, incident wavelengths, particle sizes, and material losses are analyzed and compared with the results of a circular Gaussian (CG) beam in detail. The observed dependence of the separation of optically bound particles on the incidence of an EG beam is in agreement with earlier theoretical predictions. Accurate investigation of BF induced by an EG beam could provide an effective test for further research on BF between more complex particles, which plays an important role in using optical manipulation on particle self-assembly.

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