Metabolic Engineering to Improve Docosahexaenoic Acid Production in Marine Protist Aurantiochytrium sp. by Disrupting 2,4-Dienoyl-CoA Reductase

Docosahexaenoic acid (DHA) has attracted attention from researchers because of its pharmacological and nutritional importance. Currently, DHA production costs are high due to fermentation inefficiency; however, improving DHA yield by metabolic engineering in thraustochytrids is one approach to reduce these costs. In this study, a high-yielding (53.97% of total fatty acids) DHA production strain was constructed by disrupting polyunsaturated fatty acid beta-oxidation via knockout of the 2,4-dienyl-CoA reductase (DECR) gene (KO strain) in Aurantiochytrium sp. Slight differences in cell growth was observed in the wild-type and transformants (OE and KO), with cell concentrations in stationary of 2.65×106, 2.36×106 and 2.56×106 cells mL-1 respectively. Impressively, the KO strain yielded 21.62% more neutral lipids and 57.34% greater DHA production; moreover, the opposite was observed when overexpressing DECR (OE strain), with significant decreases of 30.49% and 64.61%, respectively. Furthermore, the KO strain showed a prolonged DHA production period with a sustainable increase from 63 to 90 h (170.03 to 203.27 mg g−1 DCW), while that of the wildtype strain decreased significantly from 150.58 to 140.10 mg g−1 DCW. This new approach provides an advanced proxy for the construction of sustainable DHA production strains for industrial purposes and deepens our understanding of the metabolic pathways of Aurantiochytrium sp

Inhibition of Four Inert Powders on the Minimum Ignition Energy of Sucrose Dust

In order to evaluate the effect of inert powder on the ignition sensitivity of sucrose dust, this study investigated the effects of NaHCO3, NaCl, NH4 H2 PO4 and Al(OH)3 on the minimum ignition energy (MIE) of sucrose dust. The results showed that all four different inert powders inhibited the MIE of sucrose dust, and all of them showed a trend that the smaller the particle size of the inert powders, the better the inhibition effect. The inhibition effect was ranked as NaHCO3 > NH4 H2 PO4 > NaCl > Al(OH)3. NaHCO3 and NH4 H2 PO4 had both physical and chemical inhibition effects, which were better compared to NaCl and Al(OH)3, which had only physical inhibition effects. Analysis of the flame images showed that the inert powder slowed down the combustion of the sucrose dust flame and reduced the flame height. No flame appeared in the region of higher inert powder concentration

Study of Parameters and Theory of Sucrose Dust Explosion

To investigate the parameters of sucrose dust explosion, the minimum ignition energy (MIE) and minimum ignition temperature (MIT) were evaluated. The experiments tested the MIE of sucrose dust under different conditions of dust quantity, ignition delay time (IDT), and powder injection pressure (PIP). The experiments tested the MIT of different particle sizes. The results demonstrate that the MIE of sucrose powder under three conditions was an open-up quadratic polynomial. When the dust quantity, the IDT, and PIP were 0.5 g (417 g/m3), 90 ms, and 150 kPa, respectively, the MIE was 58.9 mJ, 62.6 mJ, and 52.4 mJ. The MIT was positively correlated with the particle size of sucrose dust, and the MIT was 340 °C. At the molecular level, the 'O–H' bonds of the sucrose molecule hydroxyl groups were broken by the discharge of electrodes or high temperature to generate H2. The combustion of H2 caused the explosion to spread to the surrounding sucrose dust and made the deposited dust rise, forming an interlocking explosion. The explosion would not stop until the dust concentration dropped below the lowest explosion limit. The results of this study can provide guidance for sucrose enterprises to prevent dust explosion accident

Investigation of an Intensifying-flux Variable Flux-leakage Interior Permanent Magnet Machine for Wide Speed Range

In this paper, a novel intensifying-flux variable flux-leakage interior permanent magnet (IFVF-IPM) machine is proposed, in which flux barriers were designed deliberately between the adjacent poles to obtain intensifying-flux effect and variable flux-leakage property. The rotor topology and design principles of the proposed machine are also introduced. Then, a multi-objective optimization method is adopted based on the sensitivity analysis, and some design variables of IFVF-IPM machine with strong sensitivity are selected to optimization progress by using the non-dominated sorting genetic algorithm-II (NSGA-II). Moreover, the electromagnetic characteristics of conventional IPM machine, conventional IFVF-IPM machine (CIFVF-IPM) and the novel IFVF-IPM machine are compared based on the finite element analysis (FEA) method which includes flux linkage, inductances characteristic, torque-speed envelops and power characteristic, as well as evaluation of the risk of irreversible demagnetization. Finally, the experiment results show that the IFVF- IPM machine has a better performance in flux weakening capability for wide speed range and a lower risk of irreversible demagnetization, which indicates the validity and feasibility of the proposed machine

Study of Explosion Characteristics and Mechanism of Sucrose Dust

In order to investigate the explosion mechanism of sucrose in the air atmosphere, the explosion intensity under different ignition delay times (IDT), powder input pressures (PIP), and concentrations were studied using a 20L-sphere. The sucrose particles were analyzed in a synchronized thermal analyzer (STA) and scanning electron microscope (SEM). The results are as follows: 1. The DSC curve has two endothermic peaks and one exothermic peak, respectively at T = 180.5 ℃, 510.2 ℃ and 582.6 ℃. 2. The explosion intensity varies with the experiment conditions. The maximum explosion pressure (Pmax) appears when IDT = 90 ms, PIP = 1.5 MPa and concentration = 625 g/m3. 3. The explosive mechanism is a homogeneous combustion mechanism based on particle surface pyrolysis and volatilization. Because of the decomposition, H2, CO, furfural, and other flammable gas-phase products are released, then surface burn appears, which leads to the crystal rupture on account of thermal imbalance, resulting in multiple flame points and a chain explosion. As the temperature of the 20L-sphere rises, more explosive products are released, which causes a rapidly expanding explosion and eventually forms the explosion. This paper can be used as a reference for the prevention of explosion accidents in sucrose production processing

Acupuncture Treatment for Cough-Variant Asthma: A Meta-Analysis

Background. In recent years, there have been many clinical reports on acupuncture treatment of cough-variant asthma, but no researcher has objectively analysed and evaluated the efficacy and safety of acupuncture treatment of cough-variant asthma from the perspective of evidence-based medicine. Objective. To systematically evaluate the clinical efficacy and safety of acupuncture in treating cough-variant asthma and to provide reference values for clinical decision-making. Methods. The comprehensive computer retrieval Chinese journal full-text database (CNKI), Chinese science and technology periodical database (VIP), ten thousand data knowledge service platform (WanFang Data), PubMed, Embase, and the Cochrane Library were used to collect literature for relevant randomized controlled trials (RCT) of acupuncture treatment of cough-variant asthma, as well as to retrieve papers and add reference retrieval after literature review, in accordance with the standard of literature filtering, data extraction, and quality evaluation. The data were meta-analysed using ReviewManager5.3 software recommended by Cochrane. Results. A total of 11 randomized controlled clinical studies were screened and included, comprising 929 patients. The results of the meta-analysis showed that, compared with the control group, acupuncture intervention on CVA could enhance the total clinical effectiveness rate, reduce the relapse rate of drug withdrawal, relieve symptoms of cough, phlegm, and diaphragmatic congestion, and improve lung function-related indicators and immune inflammation indicators. There were statistically significant differences in all efficacy evaluation criteria. Conclusion. The clinical curative effect of acupuncture treatment for cough-variant asthma is precise and has certain advantages in relieving symptoms and reducing the recurrence rate. However, the low quality of the evaluation in the RCT research literature is a problem, and more high-quality clinical randomized controlled trials are needed to further verify the comprehensive clinical efficacy and safety of this treatment. Registration number: PROSPERO (no. CRD42020155244) (https://www.crd.york.ac.uk/prospero/)

Grafting Propagation Techniques of Red Sandalwood (Pterocarpus santalinus), a Precious Hongmu Tree Species

[Objectives] This article aimed to study the grafting propagation techniques of red sandalwood (Pterocarpus santalinus), so as to provide technical support for the effective propagation of seedlings of this precious Hongmu species. [Methods] Based on the analysis and comparison of the growth performance of the Hongmu tree species introduced to China, taking 1 to 2-year-old  Pterocarpus indicus seedlings as rootstocks and single-bud stems of P. santalinus as scions, grafting was carried out from January to April using three grafting propagation methods, cut grafting propagation, skin grafting propagation and oblique grafting propagation. [Results] The results of several years of experiments show that in early spring, P. santalinus could be propagated well using the grafting propagation methods of skin grafting propagation and oblique grafting propagation, with survival rate over 80%. For rootstocks with young age or thin stems, the joint unions of the oblique grafting propagation healed well, without apparent protrusions, unlike those of skin grafting propagation. The survival rate of oblique grafting propagation that is fast and reliable was higher than that of cut grafting propagation. [Conclusions] It is feasible to use the grafting propagation methods to propagate P. santalinus seedlings. This is a traditional and innovative technology path in the in the propagation of high-quality seedlings of precious Hongmu trees, and can be promoted and applied in industrial practice

Molecular Characterization and Immune Protection of a New Conserved Hypothetical Protein of Eimeria tenella.

The genome sequences of Eimeria tenella have been sequenced, but >70% of these genes are currently categorized as having an unknown function or annotated as conserved hypothetical proteins, and few of them have been studied. In the present study, a conserved hypothetical protein gene of E. tenella, designated EtCHP559, was cloned using rapid amplification of cDNA 5'-ends (5'RACE) based on the expressed sequence tag (EST). The 1746-bp full-length cDNA of EtCHP559 contained a 1224-bp open reading frame (ORF) that encoded a 407-amino acid polypeptide with the predicted molecular weight of 46.04 kDa. Real-time quantitative PCR analysis revealed that EtCHP559 was expressed at higher levels in sporozoites than in the other developmental stages (unsporulated oocysts, sporulated oocysts and second generation merozoites). The ORF was inserted into pCold-TF to produce recombinant EtCHP559. Using western blotting, the recombinant protein was successfully recognized by rabbit serum against E. tenella sporozoites. Immunolocalization by using EtCHP559 antibody showed that EtCHP559 was mainly distributed on the parasite surface in free sporozoites and became concentrated in the anterior region after sporozoites were incubated in complete medium. The EtCHP559 became uniformly dispersed in immature and mature schizonts. Inhibition of EtCHP559 function using anti-rEtCHP559 polyclonal antibody reduced the ability of E. tenella sporozoites to invade host cells by >70%. Animal challenge experiments demonstrated that the recombinant EtCHP559 significantly increased the average body weight gain, reduced the oocyst outputs, alleviated cecal lesions of the infected chickens, and resulted in anticoccidial index >160 against E. tenella. These results suggest that EtCHP559 plays an important role in sporozoite invasion and could be an effective candidate for the development of a new vaccine against E. tenella

Microcosmic Characteristics of Hydrate Formation and Decomposition in the Different Particle Size Sediments Captured by Cryo-SEM

Sand production and sand control studies in non-diagenetic reservoirs are the weak point in the conventional petroleum industry. However, natural gas hydrate (NGH) mainly exists in non-diagenetic strata, and sand production occurs during exploitation, which restricts the safe and sustainable production of NGH. To study the microcosmic characteristics of sand production, the hydrate decomposition behaviours in the sediments were captured by the Cryo-SEM method. The micromorphology of different particle sizes of sand samples containing NGH (the sand median diameter d50 is 150, 87, 55, 38, 24, and 13 µm) and the microcosmic processes of NGH decomposition were observed. Then, the microcosmic characteristics of sand production, during the decomposition process, were analysed. (1) The gas hydrate decomposition increases pore space and reduces reservoir strength; the expansion action of the decomposition of water and gas, the softening action of the decomposition of water, and the compression action by overlying stress (crustal stress) promoted sand production, deformation, and subsidence of the NGH reservoirs in the mining process. (2) The decomposition of NGH has a more significant impact on sediments with smaller particle sizes. (3) The particle size of NGH may be larger than the particle size of the mud in the reservoirs, and acting as “gravel” plays a particular role in sand control. Therefore, the particle size of NGH cannot be ignored in the design of sand control. (4) It has been revealed, and verified, that sputtering (splashing) is a unique process of sand production caused by NGH decomposition. In other words, the rapid expansion of the volume of the decomposed gas and water from NGH leads to the eruption and sputtering of hydrate particles, providing the driving force for sand migration, which is a different process of sand production than in conventional oil and gas