• Bulletin of the Korean Chemical Society
• /
• v.33 no.1
• /
• pp.215-220
• /
• 2012

ZnO nanoparticles were synthesized through a facile route and were used as ozonation catalysts. With the increase of calcination temperature ($150-300^{\circ}C$), surface hydroxyl groups and catalytic efficiency of asobtained ZnO decreased remarkably, and the ZnO obtained at $150^{\circ}C$ showed the best catalytic activity. Compared with ozonation alone, the degradation efficiency of phenol increased above 50% due to the catalysis of ZnO-150. In the reaction temperatures range from $5^{\circ}C$ to $35^{\circ}C$, ZnO nanocatalyst revealed remarkable catalytic properties, and the catalytic effect of ZnO was better at lower temperature. Through the effect of tertbutanol on degradation of phenol and the catalytic properties of ZnO on degradation of nitrobenzene, it was proposed that the degradation of phenol was ascribed to the direct oxidation by ozone molecules based on solidliquid interface reaction.

• Bulletin of the Korean Chemical Society
• /
• v.31 no.10
• /
• pp.2830-2834
• /
• 2010

The degradation efficiencies of phenol in aqueous solution were studied by semi-continuous experiments in the processes of ozone alone, ozone/bulky $Co_3O_4$ and ozone/$Co_3O_4$ nanoparticles. Catalyst samples (bulky $Co_3O_4$ and $Co_3O_4$ nanoparticles) were characterized by X-ray diffraction and transmission electron microscopy. The Brunauer-Emmett-Teller surface area, $pH_{pzc}$ and the density of surface hydroxyl groups of the two catalyst samples were also measured. The catalytic activity of $Co_3O_4$ nanoparticles was investigated for the removal of phenol in aqueous solutions under different reaction temperatures. Tert-butyl alcohol had little effect on the catalytic ozonation processes. Based on these results, the possible catalytic ozonation mechanism of phenol by $Co_3O_4$ nanoparticles was proposed as a reaction process between ozone molecules and pollutants.

• Bulletin of the Korean Chemical Society
• /
• v.33 no.12
• /
• pp.4015-4022
• /
• 2012

Manganese(III) 5-(4-carboxyphenyl)-10,15,20-triphenyl porphyrin chloride (Mn(TCPP)Cl) was grafted through amide bond on silica zeolite Y (HY), zeolite beta ($H{\beta}$) and hexagonal mesoporous silica (HMS). XRD, ICP-AES, $N_2$ physisorption, SEM, TEM, FTIR and thermal analysis were employed to analyse these novel heterogeneous materials. These silica supported catalysts were shown to be used for epoxidation and good shape selectivity was observed. The effect of support structure on catalytic performance was also discussed. The catalytic activity remained when the catalysts were recycled five times. The energy changes about epoxidation of alkenes by $NaIO_4$ and $H_2O_2$ were also computationally calculated to explain the different catalytic efficiency.

• Current Optics and Photonics
• /
• v.6 no.3
• /
• pp.323-331
• /
• 2022

Electro-optic modulator (EOM) takes a vital role in connecting the electric and optical fields. Here, we present a heterogeneously integrated EOM based on the lithium niobate-on-insulator (LNOI) platform. The key modulation waveguide structure is a field-enhanced slot waveguide formed by embedding silicon nanowires in a thin-film lithium niobate (LN), which is different from the previously reported LN ridge or etchless LN waveguides. Based on such slot structure, optical mode field area is reduced and enhanced electric field in the slot region can interact well with LN material with high Electro-optic (EO) coefficient. Therefore, the improvements in both aspects have positive effects on enhancing the modulation performance. From results, the corresponding EOM by adding such modulation waveguide structure achieves better performance, where the key half-wave-voltage-length product (V_𝜋L) and 3 dB EO bandwidth are 1.78 V·cm and 40 GHz under the electrode gap width of only 6 ㎛, respectively. Moreover, Lower V_𝜋L can also be achieved. With these characteristics, such field-enhanced waveguide structure could further promote the development of LNOI-based EOM.

• Journal of Microbiology and Biotechnology
• /
• v.33 no.10
• /
• pp.1257-1267
• /
• 2023

Although rational genetic engineering is nowadays the favored method for microbial strain improvement, building up mutant libraries based on directed evolution for improvement is still in many cases the better option. In this regard, the demand for precise and efficient screening methods for mutants with high performance has stimulated the development of biosensor-based high-throughput screening strategies. Genetically encoded biosensors provide powerful tools to couple the desired phenotype to a detectable signal, such as fluorescence and growth rate. Herein, we review recent advances in engineering several classes of biosensors and their applications in directed evolution. Furthermore, we compare and discuss the screening advantages and limitations of two-component biosensors, transcription-factor-based biosensors, and RNA-based biosensors. Engineering these biosensors has focused mainly on modifying the expression level or structure of the biosensor components to optimize the dynamic range, specificity, and detection range. Finally, the applications of biosensors in the evolution of proteins, metabolic pathways, and genome-scale metabolic networks are described. This review provides potential guidance in the design of biosensors and their applications in improving the bioproduction of microbial cell factories through directed evolution.

• Journal of Microbiology and Biotechnology
• /
• v.18 no.2
• /
• pp.322-327
• /
• 2008

1,5-Dihydroxy-3-methoxy-7-methylanthracene-9,10-dione (shiraiarin) is a kind of antitumor and antibacterial anthraquinone, and was produced for the first time from the submerged fermentation of Shiraia bambusicola, as confirmed by ESI-MS and NMR. The production of shiraiarin was significantly influenced when varying the carbon source, and a high amount of shiraiarin was only achieved when using lactose. The production of shiraiarin was also stimulated when using $NaNO_3$ as the nitrogen source, whereas other nitrogen sources inhibited its production. Shiraiarin was formed during the stationary phase with a pH value higher than 8. The production of shiraiarin was inhibited by sporulation.

• Journal of Microbiology and Biotechnology
• /
• v.28 no.11
• /
• pp.1850-1858
• /
• 2018

Glucosamine (GlcN) is widely used in the nutraceutical and pharmaceutical industries. Currently, GlcN is mainly produced by traditional multistep chemical synthesis and acid hydrolysis, which can cause severe environmental pollution, require a long prodution period but a lower yield. The aim of this work was to develop a whole-cell biocatalytic process for the environment-friendly synthesis of glucosamine (GlcN) from N-acetylglucosamine (GlcNAc). We constructed a recombinant Escherichia coli and Bacillus subtilis strains as efficient whole-cell biocatalysts via expression of diacetylchitobiose deacetylase ($Dac_{ph}$) from Pyrococcus furiosus. Although both strains were biocatalytically active, the performance of B. subtilis was better. To enhance GlcN production, optimal reaction conditions were found: B. subtilis whole-cell biocatalyst 18.6 g/l, temperature $40^{\circ}C$, pH 7.5, GlcNAc concentration 50 g/l and reaction time 3 h. Under the above conditions, the maximal titer of GlcN was 35.3 g/l, the molar conversion ratio was 86.8% in 3-L bioreactor. This paper shows an efficient biotransformation process for the biotechnological production of GlcN in B. subtilis that is more environmentally friendly than the traditional multistep chemical synthesis approach. The biocatalytic process described here has the advantage of less environmental pollution and thus has great potential for large-scale production of GlcN in an environment-friendly manner.

• Journal of Microbiology and Biotechnology
• /
• v.28 no.7
• /
• pp.1052-1060
• /
• 2018

Numerous studies suggest that the effects of lactic acid bacteria (LAB) on oxidative stress in vivo are correlated with their antioxidative activities in vitro; however, the relationship is still unclear and contradictory. The antioxidative activities of 27 Lactobacillus plantarum strains isolated from fermented foods were determined in terms of 2,2-diphenyl-1-picrylhydrazyl, hydroxyl radical, and superoxide radical scavenging abilities, reducing activity, resistance to hydrogen peroxide, and ferrous chelating ability in vitro. Two fuzzy synthetic evaluation models, one with an analytic hierarchy process and one using entropy weight, were then used to evaluate the overall antioxidative abilities of these L. plantarum strains. Although there was some difference between the two models, the highest scoring strain (CCFM10), the middle scoring strain (CCFM242), and the lowest scoring strain (RS15-3) were obtained with both models. Examination of the antioxidative abilities of these three strains in $\text\tiny{D}$-galactose-induced oxidative stress mice demonstrated that their overall antioxidative abilities in vitro could reveal the abilities to alleviate oxidative stress in vivo. The current study suggests that assessment of overall antioxidative abilities with fuzzy synthetic models can guide the evaluation of probiotic antioxidants. It might be a more quick and effective method to evaluate the overall antioxidative abilities of LAB.

• Bulletin of the Korean Chemical Society
• /
• v.34 no.11
• /
• pp.3227-3232
• /
• 2013

A novel Cu-Co-O composite nanocatalyst was designed and prepared for the ozonation of phenol. A synergistic effect of copper and cobalt was observed over the Cu-Co-O composite nanocatalyst, which showed higher activity than either copper or cobalt oxide alone. In addition, the Cu-Co-O composite revealed good activity in a wide initial pH range (4.11-8.05) of water. The fine dispersion of cobalt on the surface of copper oxide boosted the interaction between catalyst and ozone, and the surface Lewis acid sites on the Cu-Co-O composite were determined as the active sites. The Raman spectroscopy also proved that the Cu-Co-O composite was quite sensitive to the ozone. The trivalent cobalt in the Cu-Co-O composite was proposed as the valid state.

• ETRI Journal
• /
• v.38 no.5
• /
• pp.1019-1029
• /
• 2016

The probability hypothesis density (PHD) filter is an effective means to track multiple targets in that it avoids explicit data associations between the measurements and targets. However, the target birth intensity as a prior is assumed to be known before tracking in a traditional target-tracking algorithm; otherwise, the performance of a conventional PHD filter will decline sharply. Aiming at this problem, a novel target birth intensity scheme and an improved measurement-driven scheme are incorporated into the PHD filter. The target birth intensity estimation scheme, composed of both PHD pre-filter technology and a target velocity extent method, is introduced to recursively estimate the target birth intensity by using the latest measurements at each time step. Second, based on the improved measurement-driven scheme, the measurement set at each time step is divided into the survival target measurement set, birth target measurement set, and clutter set, and meanwhile, the survival and birth target measurement sets are used to update the survival and birth targets, respectively. Lastly, a Gaussian mixture implementation of the PHD filter is presented under a linear Gaussian model assumption. The results of numerical experiments demonstrate that the proposed approach can achieve a better performance in tracking systems with an unknown newborn target intensity.