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Search Results: 1 - 10 of 80872 matches for " Yuhuan Liu "
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Identification and characterization of a novel thermostable pyrethroid-hydrolyzing enzyme isolated through metagenomic approach
Xinjiong Fan, Xiaolong Liu, Rui Huang, Yuhuan Liu
Microbial Cell Factories , 2012, DOI: 10.1186/1475-2859-11-33
Abstract: In this study, we identified a novel pyrethroid-hydrolyzing enzyme Sys410 belonging to familyV esterases/lipases with activity-based functional screening from Turban Basin metagenomic library. Sys410 contained 280 amino acids with a predicted molecular mass (Mr) of 30.8 kDa and was overexpressed in Escherichia coli BL21 (DE3) in soluble form. The optimum pH and temperature of the recombinant Sys410 were 6.5 and 55°C, respectively. The enzyme was stable in the pH range of 4.5-8.5 and at temperatures below 50°C. The activity of Sys410 decreased a little when stored at 4°C for 10 weeks, and the residual activity reached 94.1%. Even after incubation at 25°C for 10 weeks, it kept 68.3% of its activity. The recombinant Sys410 could hydrolyze a wide range of ρ-nitrophenyl esters, but its best substrate is ρ-nitrophenyl acetate with the highest activity (772.9 U/mg). The enzyme efficiently degraded cyhalothrin, cypermethrin, sumicidin, and deltamethrin under assay conditions of 37°C for 15 min, with exceeding 95% hydrolysis rate.This is the first report to construct metagenomic libraries from Turban Basin to obtain the thermostable pyrethroid-hydrolyzing enzyme. The recombinant Sys410 with broad substrate specificities and high activity was the most thermostable one of the pyrethroid-hydrolyzing esterases studied before, which made it an ideal candidate for the detoxification of pyrethroids.Pyrethroid pesticides are synthetic analogues of pyrethrins, which are natural chemicals derived from Chrysanthemum flowers [1]. They are also used as broad-spectrum pest control agents in agricultural production, thanks to their high toxicities to insects and low toxicities to mammals [2]. Currently, organophosphorous pesticides are increasingly being replaced by pyrethroid pesticides, and the impact of the pyrethroid pesticides residual on the environment is likely to draw more attention [3,4]. Both agricultural and residential usage is continuing to grow [5], leading to the developmen
Solving Large Scale Nonlinear Equations by a New ODE Numerical Integration Method  [PDF]
Tianmin Han, Yuhuan Han
Applied Mathematics (AM) , 2010, DOI: 10.4236/am.2010.13027
Abstract: In this paper a new ODE numerical integration method was successfully applied to solving nonlinear equations. The method is of same simplicity as fixed point iteration, but the efficiency has been significantly improved, so it is especially suitable for large scale systems. For Brown’s equations, an existing article reported that when the dimension of the equation N = 40, the subroutines they used could not give a solution, as compared with our method, we can easily solve this equation even when N = 100. Other two large equations have the dimension of N = 1000, all the existing available methods have great difficulties to handle them, however, our method proposed in this paper can deal with those tough equations without any difficulties. The sigularity and choosing initial values problems were also mentioned in this paper.
Solving Load Flow Problems of Power System by Explicit Pseudo-Transient Continuation (E-ψtc) Method  [PDF]
Tianmin Han, Yuhuan Han
Energy and Power Engineering (EPE) , 2016, DOI: 10.4236/epe.2016.82009
Abstract: This paper is a further study of two papers [1] and [2], which were related to Ill-Conditioned Load Flow Problems and were published by IEEE Trans. PAS. The authors of this paper have some different opinions, for example, the 11-bus system is not an ill-conditioned system. In addition, a new approach to solve Load Flow Problems, E-ψtc, is introduced. It is an explicit method; solving linear equations is not needed. It can handle very tough and very large systems. The advantage of this method has been fully proved by two examples. The authors give this new method a detailed description of how to use it to solve Load Flow Problems and successfully apply it to the 43-bus and the 11-bus systems. The authors also propose a strategy to test the reliability, and by solving gradient equations, this new method can answer if the solution exists or not.
Current Status and Prospects of Biodiesel Production from Microalgae
Xiaodan Wu,Rongsheng Ruan,Zhenyi Du,Yuhuan Liu
Energies , 2012, DOI: 10.3390/en5082667
Abstract: Microalgae represent a sustainable energy source because of their high biomass productivity and ability to remove air and water born pollutants. This paper reviews the current status of production and conversion of microalgae, including the advantages of microalgae biodiesel, high density cultivation of microalgae, high-lipid content microalgae selection and metabolic control, and innovative harvesting and processing technologies. The key barriers to commercial production of microalgae biodiesel and future perspective of the technologies are also discussed.
An Inverse Problem for a Class of Linear Stochastic Evolution Equations
Yuhuan Zhao
Journal of Applied Mathematics , 2012, DOI: 10.1155/2012/921038
Abstract: An inverse problem for a linear stochastic evolution equation is researched. The stochastic evolution equation contains a parameter with values in a Hilbert space. The solution of the evolution equation depends continuously on the parameter and is Fréchet differentiable with respect to the parameter. An optimization method is provided to estimate the parameter. A sufficient condition to ensure the existence of an optimal parameter is presented, and a necessary condition that the optimal parameter, if it exists, should satisfy is also presented. Finally, two examples are given to show the applications of the above results.
Molecular modification and degradation characteristics of a novel marine mud-derived pyrethroid hydrolase

LIU Xiaolong
, LIU Yuhuan,FAN Xinjiong

- , 2017,
Abstract: 为了获得稳定性和酶活性提高的拟除虫菊酯类降解酶,利用易错PCR技术对来源于海底泥宏基因组文库的新型酯酶基因(est825)进行体外定向进化,获得了一个酶活性和热稳定性均提高的突变酶(EstM46)。与野生型相比其酶活力提高1.5倍;最适反应温度提高了5 ℃,同时热稳定性明显增强。此外,EstM46对氯氟氰菊酯、氯氰菊酯、氰戊菊酯和溴氰菊酯的降解率分别提升至92.21%、99.75%、93.21%和89.48%。这对降低酶的生产成本、促进工业化发展和环境保护有重要意义

Liu Yuhuan,Zhong Yingchang,

微生物学报 , 2000,
Abstract: Degrading enzyme of organophosophorus pesticides was purified from Aspergillus oryzeZ58 by (NH4)2SO4 precipitation, Sephadex G-100 gel filtration, DEAE-cellulose chromatography with 34.2-fold purification, 17.8% recovery and 76.2 U/mg specific activity. The purified enzyme was homogeneous on polyacrylamide gel electrophoresis. The molecular weight of the enzyme estimated with Sephadex G-100 was 67000. The optimal conditions for activity were pH 7.2, temperature 45 degrees C. The enzyme was stable over the range of pH 6-10 and below 40 degrees C, the activity was inhibited by SDS and stimulated by Cu2+, the substrate ranges were nonspecific to organophosophorus pesticides.
Dairy Products Consumption and Risk of Type 2 Diabetes: Systematic Review and Dose-Response Meta-Analysis
Dengfeng Gao, Ning Ning, Congxia Wang, Yuhuan Wang, Qing Li, Zhe Meng, Yang Liu, Qiang Li
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0073965
Abstract: Background The consumption of dairy products may influence the risk of type 2 diabetes mellitus (T2DM), but inconsistent findings have been reported. Moreover, large variation in the types of dairy intake has not yet been fully explored. Methods and Results We conducted a systematic review and meta-analysis to clarify the dose–response association of dairy products intake and T2DM risk. We searched PubMed, EMBASE and Scopus for studies of dairy products intake and T2DM risk published up to the end of October 2012. Random-effects models were used to estimate summary relative risk (RR) statistics. Dose-response relations were evaluated using data from different dairy products in each study. We included 14 articles of cohort studies that reported RR estimates and 95% confidence intervals (95% CIs) of T2DM with dairy products intake. We found an inverse linear association of consumption of total dairy products (13 studies), low-fat dairy products (8 studies), cheese (7 studies) and yogurt (7 studies) and risk of T2DM. The pooled RRs were 0.94 (95% CI 0.91–0.97) and 0.88 (0.84–0.93) for 200 g/day total and low-fat dairy consumption, respectively. The pooled RRs were 0.80 (0.69–0.93) and 0.91 (0.82–1.00) for 30 g/d cheese and 50 g/d yogurt consumption, respectively. We also found a nonlinear association of total and low-fat dairy intake and T2DM risk, and the inverse association appeared to be strongest within 200 g/d intake. Conclusion A modest increase in daily intake of dairy products such as low fat dairy, cheese and yogurt may contribute to the prevention of T2DM, which needs confirmation in randomized controlled trials.
Solving Large Scale Unconstrained Minimization Problems by a New ODE Numerical Integration Method  [PDF]
Tianmin Han, Xinlong Luo, Yuhuan Han
Applied Mathematics (AM) , 2011, DOI: 10.4236/am.2011.25069
Abstract: In reference [1], for large scale nonlinear equations , a new ODE solving method was given. This paper is a continuous work. Here has gradient structure i.e. , is a scalar function. The eigenvalues of the Jacobian of ; or the Hessian of , are all real number. So the new method is very suitable for this structure. For quadratic function the convergence was proved and the spectral radius of iteration matrix was given and compared with traditional method. Examples show for large scale problems (dimension ) the new method is very efficient.
Advances of metagenomics in discovering novel biocatalysts

Kui Wang,Sidi Wang,Rui Huang,Yuhuan Liu,

生物工程学报 , 2012,
Abstract: Microorganisms contain a large number of biocatalysts, which are of great potential in industrial applications. However, the traditional cultural approaches can obtain only less than 1% of microorganisms. As a culture-independent method, metagenomics is an advanced solution by means of extracting all microbial genomic DNAs in certain environmental habitat, constructing and screening metagenomic libraries to seek novel functional genes. It serves as an effective tool for studying these uncultured microorganisms. Therefore, mining novel biocatalysts from metagenome has drawn the attention of researchers in the world. In this paper, environment sample category, genomic DNA extraction, library construction and screening strategies were reviewed. Recent examples of isolated biocatalysts from metagenomic libraries were presented. Future research directions of metagenomics were also discussed.
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