An extremely thermostable maltogenic amylase from <i>Staphylothermus marinus</i>: <i>Bacillus</i> expression of the gene and its application in genistin glycosylation

Li, Xiaolei,Wang, Yujuan,Park, Jong-Tae,Gu, Liwei,Li, Dan Elsevier 2018 INTERNATIONAL JOURNAL OF BIOLOGICAL MACROMOLECULES Vol.107 No.1

<P><B>Abstract</B></P> <P>The most extremely thermostable maltogenic amylase (SMMA) from archaeon <I>Staphylothermus marinus</I> has many potential applications in food processing. To ensure safety of microbial origin, a recombinant plasmid containing the enzymic gene and a constitutive promoter AmyR2 was constructed, and then transformed into a GRAS microorganism <I>Bacillus subtilis</I>. The purified SMMA from the liquid cultures of <I>Bacillus</I> has a specific activity of 66.96U/mg, two times more than that from <I>Escherichia coli</I>. SMMA was further employed to catalyze the genistion glycosylation using γ-CD as both glucosyl donors and solubilizer. Glycosylated genistins with one to four additional α-glucosyls and a molar percentage of 69.87% in genistin reaction mixture were identified and quantified by HPLC–UV–MS. The glycosylated genistins at 0.2–1.2mM showed an enhanced DPPH free radical scavenging capacity. To our knowledge, this is the first report on the <I>Bacillus</I> expression of archaeal maltogenic amylase.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A fused gene of SMMA and a constitutive promoter AmyR2 was transformed into <I>B. subtilis</I>. </LI> <LI> Specific activity of purified SMMA from <I>B. subtilis</I> was two times more than that from <I>E. coli</I>. </LI> <LI> SMMA of safe microbial origin attached different number of glucosyls from γ-CD to genistin at 90°C. </LI> <LI> Glycosylated genistins showed an enhanced DPPH free radical scavenging capacity than genistin. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Controlled synthesis of Co₂C nanochains using cobalt laurate as precursor: Structure, growth mechanism and magnetic properties

Zhang, Yajing,Zhu, Yuan,Wang, Kangjun,Li, Da,Wang, Dongping,Ding, Fu,Meng, Dan,Wang, Xiaolei,Choi, Chuljin,Zhang, Zhidong Elsevier 2018 Journal of magnetism and magnetic materials Vol.456 No.-

<P><B>Abstract</B></P> <P>Cobalt carbides (Co<SUB>2</SUB>C and Co<SUB>3</SUB>C) nanocomposites exhibit interesting hard magnetic property, controlled synthesis of individual phase facilitates to clarify the magnetism of each, but it is difficult to obtain the single phase. We present a new approach to address this issue via a polyol refluxing process, using cobalt laurate as the precursor. The single phase Co<SUB>2</SUB>C magnetic nanochains self-assembled by nanoparticles are synthesized. The precursor is the key factor for controlling the growth kinetics of the Co<SUB>2</SUB>C nanochains. Cobalt, instead of cobalt carbides, is produced if cobalt chloride, acetate and acetylacetonate replace cobalt laurate as the precursor, respectively. The evolution of the growth process has been studied. In the formation of Co<SUB>2</SUB>C, first fcc-Co produces, then it transforms into Co<SUB>2</SUB>C by carbon diffusion process, and the produced carbon first exists in disordered state and then a small amount of them transforms into graphite. Saturation magnetization (<I>Ms</I>) of Co<SUB>2</SUB>C nanochains obtained at 300 °C for 20, 60, and 180 min are 27.1, 18.9, and 10.9 emu g<SUP>−1</SUP>, respectively. The decrease of <I>Ms</I> caused by increasing carbon content, and the carbon content are much larger than the stoichiometric ratio value of Co<SUB>2</SUB>C (9.2 wt%). The Co<SUB>2</SUB>C nanochains have mesoporous pore of 3.8 nm and the specific surface area of 48.6 m<SUP>2</SUP> g<SUP>−1</SUP>.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The Co<SUB>2</SUB>C magnetic nanochains are synthesized using cobalt laurate as the precursor in TEG. </LI> <LI> The precursor of cobalt laurate is the key factor for controlling the growth kinetics of Co<SUB>2</SUB>C nanochains. </LI> <LI> Ms of Co<SUB>2</SUB>C nanochains obtained at 300 °C for 20, 60, and 180 min are 27.1, 18.9, and 10.9 emu g<SUP>−1</SUP>, respectively. </LI> <LI> The decrease of Ms is caused by increasing carbon content with increasing reaction time. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>We present a new approach to obtain single phase Co<SUB>2</SUB>C nanochains by using cobalt laurate as the precursor.</P> <P>[DISPLAY OMISSION]</P>

Excellent microwave absorption of FeCo/ZnO composites with defects in ZnO for regulating the impedance matching

Bao, Xiukun,Wang, Xiaolei,Zhou, Xinao,Shi, Guimei,Xu, Ge,Yu, Jin,Guan, Yinyan,Zhang, Yajing,Li, Da,Choi, Chuijin Elsevier 2018 JOURNAL OF ALLOYS AND COMPOUNDS Vol.769 No.-

<P><B>Abstract</B></P> <P>FeCo/ZnO composites have been successfully prepared through liquid-phase reduction process for the formation of FeCo polyhedrons and sequentially thermal decomposition of colloidal mixture of FeCo and Zn(Ac)<SUB>2</SUB>·2H<SUB>2</SUB>O under nitrogen atmospheres. ZnO nanoparticles are homogeneously deposited on the surface of FeCo polyhedrons and the level of oxygen-vacancy defects in ZnO can be elevated with the increase of ZnO content. By comparison with FeCo polyhedrons, FeCo/ZnO composites exhibit excellent microwave absorption. The optimal RL value can reach −34.8 dB at 14.8 GHz and effective bandwidth (RL < −10 dB) is 5.1 GHz in the frequency range of 12.4–17.5 GHz with a matching thickness of 1.5 mm. The integrated bandwidth with RL < −10 dB can reach 14.1 GHz covering 3.4–17.5 GHz. Theory analysis demonstrates the interfacial polarization, dipole polarization and high conductivity due to oxygen-vacancy defects in FeCo/ZnO composites contribute to enhancement of dielectric loss capacity, which is more favorable for impedance matching.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The preferable impedance matching of FeCo/ZnO composites can be achieved by regulating the ZnO content. </LI> <LI> The optimal reflection loss (RL) can reach −34.8 dB with a matching thickness of 1.5 mm. </LI> <LI> The effective bandwidth with RL < −10 dB achieve 14.1 GHz covering 3.4–17.5 GHz with integrated thickness of 1.5–5 mm. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Genotypic Characteristics of Haemophilus influenzae Isolates from Pediatric Pneumonia Patients in Chengdu City, Sichuan, China

Tian Guozhong,Zhang Li,Li Machao,Wang Xiaolei,Zheng Yuhong,Li Xiaojing,Huang Cheng,Li Xuechun,Xie Yongqiong,Xu Li,Ren Hongyu,Shao Zhujun 한국미생물학회 2009 The journal of microbiology Vol.47 No.4

Two hundred and seventy-three Haemophilus influenzae strains isolated from pediatric pneumonia patients in China were studied. We used Multilocus Sequence Typing (MLST) to analyze genotypic characteristics. All strains were biotyped and serotyped. Relatedness and patterns of genes among isolates were determined by the analysis of MLST and eBURST. H. influenzae primarily causes acute pneumonia in children under 1 year old. Nontypeable H. influenzae was responsible for most cases of pediatric pneumonia. All 273 strains were classified into eight biotypes. They mostly belonged to the I, II, and III biotypes (17.6%, 43.6%, and 22.7%, respectively). 62 strains (22.7%) produced β-lactamase. We found 28 novel alleles. Fifty different STs were found by MLST, of which 39 were novel. These were ST477 through ST508 and ST521 through ST527. Group 17 and predicted founders 503 were new groups in this study. No STs correlated with strains from Korea, which is adjacent to China. The H. influenzae strains from China appeared to have heterogeneous ST types patterns which may be the reason no outbreaks or epidemics of H. influenzae infections have occurred in Chengdu city, Sichuan, China.

Effects of Homopolymers and Semi-interpenetrating Net-work (sIPN) on the Micellization and Gelation of Pluronic F127 Aqueous Solutions

XIAOLEI LI,Listiana Oktavia,곽민석,현규 한국고분자학회 2016 한국고분자학회 학술대회 연구논문 초록집 Vol.41 No.1

Neonicotinoid insecticide resistance in the field populations of Sogatella furcifera (Horváth) in Central China from 2011 to 2015

Xiaolei Zhang,Xun Liao,Kaikai Mao,Peng Yang,Dongyang Li,Ehsan Ali,Hu Wan,Jian Hong Li 한국응용곤충학회 2017 Journal of Asia-Pacific Entomology Vol.20 No.3

The whitebacked planthopper Sogatella furcifera (Horváth) is an important pest of rice throughout Asia. Application of chemical insecticide is the main approach to suppress the field populations of S. furcifera. In this study, neonicotinoid insecticide resistance in field populations of S. furcifera were evaluated. The results showed that some field populations of S. furcifera had developed moderate level of resistance to imidacloprid (RR =1.1–16.4), thiamethoxam (RR=0.8–14.9), dinotefuran (RR =1.2–16.6) and acetamiprid (RR =3.3–12.2), low level of resistance to nitenpyram (RR=1.1–9.5) and clothianidin (RR =1.3–8.7) in Central China. Moreover, there were an increasing trend in neonicotinoid insecticide resistance in the period 2011–2015. The results of current study may form the basis to identify and evaluate the resistance tendency of S. furcifera against neonicotinoid insecticides, which could make effective management recommendations to avoid further development of insecticide resistance in S. furcifera.

Fabrication of Polyether Sulfone Blend Imprinted Membranes for Selective Adsorption of p-hydroxybenzonic from Salicylic Acid

Xiaolei Li,Jun Chen,Chaofen Yang 한국섬유공학회 2018 Fibers and polymers Vol.19 No.5

Highly selective polyether sulfone (PES) blend imprinted membranes for template p-hydroxybenzonic (p-HB) were synthesized by phase inversion imprinting technique using polybenzimidazoles (PBI) as a functional polymer and nanosized Al2O3 as the additives. The SEM analysis showed that cross-sectional morphology of membranes were strongly influenced by the content of nano-sized Al2O3. Compared with PES1-MIM, PES2-MIM and PES4-MIM, the PES3-MIM containing 2.0 wt.% nano-sized Al2O3 exhibited higher membrane flux, kinetic equilibrium adsorption value, binding capacity and better selectivity for p-HB. The experimental data of adsorption kinetic were well fitted to the pseudo-secondorder kinetic model using multiple regression analysis. Static adsorption isotherm experiments exhibited that the PES3-MIM had the maximum adsorption capacity for p-HB. Moreover, selective experiment showed that the selectivity coefficients of PES3-MIM for p-HB relative to salicylic acid (SA) was 3.670, showing that PES3-MIM had excellent binding affinity and selectivity for separating p-HB form p-HB-contained aqueous solution.

Rheological study of the effect of polyethylene oxide (PEO) homopolymer on the gelation of PEO-PPO-PEO triblock copolymer in aqueous solution

Li, Xiaolei,Hyun, Kyu Springer Science + Business Media 2018 Korea-Australia rheology journal Vol.30 No.2

<P>The effects of polyethylene oxide (PEO) homopolymer on the gelation behavior of a PEO100-PPO65-PEO100 triblock copolymer (Pluronic F127) were explored in aqueous solution under non-isothermal and isothermal conditions. Under non-isothermal conditions (temperature sweep test), two transition points were observed on increasing temperature, that is, at lower and upper gelation temperatures (LT(gel )and UTgel, respectively). Between LTgel and UTgel, F127 aqueous solutions maintained a hard gel state. Both molecular weight (MW) and PEO concentration affected these two gelation temperatures. In particular, relative molecular weight (MWrel = molecular weight of PEO homopolymer/PEO segment of F127) affected LTgel. LTgel decreased on increasing PEO concentration at MWrel values of <1, but increased on increasing PEO concentration at MWrel values of >1. On the other hand, UTgel decreased with increasing PEO concentration regardless of MWrel. Under isothermal conditions (fixed temperature between LTgel and UTgel), the effects of PEO homopolymer on the mechanical properties of F127 hard gel were systemically investigated using small and large amplitude oscillatory shear tests. In the linear viscoelastic regime, total intra-cycle stress and elastic intra-cycle stress were similar, and viscous response increased on increasing PEO concentration. However, at large strain amplitudes, hard gels showed intra-cycle stiffening but inter-cycle softening behavior. In addition, on increasing PEO concentrations, viscous nonlinearities underwent strain-rate thickening followed by strain-rate thinning.</P>

Rheological analysis of core-stabilized Pluronic F127 by semi-interpenetrating network (sIPN) in aqueous solution

Li, Xiaolei,Park, Eun-kyoung,Hyun, Kyu,Oktavia, Listiana,Kwak, Minseok Society of Rheology 2018 Journal of rheology Vol.62 No.1

<P>A poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer (Pluronic F127) micelle system was stabilized using an ultraviolet-induced semi-interpenetrating network (sIPN). The sIPN structure within the micelle cores was found to stabilize the micelles against low temperatures, but affected the resulting material properties. In this study, the rheological properties of Pluronic F127 with sIPN (F127-sIPN) and without sIPN (F127) were compared. The presence of the sIPN structure increased the gelation temperature (T-gel) at the same concentration, and unlike F127, F127-sIPN exhibited strong heating rate dependent and thermodynamically irreversible behaviors. Hard gels containing various concentrations of F127-sIPN and F127 were investigated at 40 degrees C. At concentrations above 18 wt. %, both F127-sIPN and F127 exhibited similar linear viscoelastic properties due to the tight, ordered core-shell micelles packing, but the two systems exhibited different behaviors below 18 wt. % concentration. To investigate this difference, hard gels with 16 wt. % F127-sIPN and F127 were selected, and two types of nonlinear rheological tests were conducted, i.e., large amplitude oscillatory shear (LAOS) and strain-rate frequency superposition (SRFS) tests. The cage modulus of F127-sIPN obtained from LAOS testing showed it maintained its elastic contribution over the large deformation region meaning that a loose core network still existed. The relaxation time spectrum of F127-sIPN obtained by SRFS testing indicated it had two relaxation modes (fast and slow) whereas that for F127 had only a fast mode. The slow relaxation mode of F127-sIPN is associated with crosslinking of the sIPN. Since these behaviors were not observed in linear rheological tests, it was concluded that nonlinear rheological tests provide more structural information about hard gels. (C) 2017 The Society of Rheology.</P>

Composition and Antioxidative Properties of the Flavonoid-rich Fractions from Tartary Buckwheat Grains

Dan Li,Xiaolin Ding,Xiaolei Li 한국식품과학회 2010 Food Science and Biotechnology Vol.19 No.3

Tartary buckwheat, a healthy food, is associated with a reduced risk of certain human chronic diseases;however, its bioactive components are unknown. This study used high performance liquid chromatographyphotodiode array-mass spectroscopy (HPLC-PDA-MS) to identify the flavonoids in flavonoid-rich fractions (FRFs)from tartary buckwheat grain and tested antioxidative capacity of FRFs to confirm their bioactivity. Ultraviolet (UV) absorption and electrospray ionization (ESI−) MS/MS spectra identified several flavonols in the embryo,endosperm, testa, and hull, including the predominant flavonoid rutin and minor flavonoids quercetin 3-Orutinoside-3'-O-β-glucopyranoside, kaempferol 3-O-rutinoside,and quercetin. Tartary buckwheat FRFs extended the Rancimat induction period of lard less than common buckwheat FRF did, while their scavenging rate of DPPH free radicals exceeded that of common buckwheat FRF and rutin. These results indicate that tartary buckwheat FRFs from the grains have potential health benefits.