Publications by authors named "Yong-Keun Choi"

27 Publications

  • Page 1 of 1

Adsorptive removal of crude petroleum oil from water using floating pinewood biochar decorated with coconut oil-derived fatty acids.

Sci Total Environ 2021 Mar 21;781:146636. Epub 2021 Mar 21.

Department of Biological Engineering, College of Engineering, Konkuk University, Seoul 05029, Republic of Korea. Electronic address:

The present investigation deals with the adsorptive removal of crude petroleum oil from the water surface using coconut oil-modified pinewood biochar. Biochar generated at higher pyrolysis temperature (700 °C) revealed higher fatty acid-binding efficiency responsible for the excellent hydrophobicity of the biochar. Fatty acids composition attached to the biochar produced at 700 °C was (mg g BC) lauric acid (9.024), myristic acid (5.065), palmitic acid (2.769), capric acid (1.639), oleic acid (1.362), stearic acid (1.114), and linoleic acid (0.130). Simulation of the experimental adsorption data of pristine and modified pinewood biochar generated at 700 °C offered the best fit to pseudo-first-order kinetics (R > 0.97) and Langmuir isotherm model (R > 0.99) based on the highest regression coefficients. Consequently, the adsorption process was mainly driven by surface hydrophobic interactions including π-π electron-donor-acceptor between electron-rich (π-donor) polycyclic aromatic hydrocarbons from the crude oil and biochar (π-acceptor). A maximum adsorption capacity (Q) of 5.315 g g was achieved by modified floating biochar within 60 min. Whereas the reusability testing revealed 49.39% and 51.40% was the adsorption efficiency of pristine and modified biochar at the fifth adsorption-desorption cycle.
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http://dx.doi.org/10.1016/j.scitotenv.2021.146636DOI Listing
March 2021

Removal of Fluoride from Water Using a Calcium-Modified Dairy Manure-Derived Biochar.

J Environ Eng (New York) 2020 Dec;146(12):1-10

Dept. of Civil and Environmental Engineering, Southern Methodist Univ., Dallas, TX 75275.

This study investigated the removal of fluoride from water using a calcium-modified dairy manure-derived biochar (Ca-DM500). The Ca-DM500 showed a 3.82 - 8.86 times higher removal of fluoride from water than the original (uncoated) manure-derived biochar (DM500). This is primarily attributed to strong precipitation/complexation between fluoride and calcium. The Freundlich and Redlich-Peterson sorption isotherm models better described the experimental data than the Langmuir model. Additionally, the removal kinetics were well described by the intraparticle diffusion model. The Ca-DM500 showed high reactivity per unit surface area [0.0001, 0.03, 0.16 mg F per m for Douglas fir-derived biochar (DF-BC), DM500. and Ca-DM500, respectively] for retention of fluoride reflecting the importance of surface complexation. The copresence of anions reduced removal by Ca-DM500 in the order . The sorption behavior of fluoride in a continuous fixed-bed column was consistent with the Thomas model. Column studies demonstrated that the Ca-DM500 shows a strong affinity for fluoride, a low release potential, and a stable (unreduced) removal capacity through regeneration and reuse cycles.
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http://dx.doi.org/10.1061/(asce)ee.1943-7870.0001812DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7970507PMC
December 2020

Biowaste-to-bioplastic (polyhydroxyalkanoates): Conversion technologies, strategies, challenges, and perspective.

Bioresour Technol 2021 Apr 19;326:124733. Epub 2021 Jan 19.

Department of Biological Engineering, College of Engineering, Konkuk University, Seoul 05029, Republic of Korea; Institute for Ubiquitous Information Technology and Application, Konkuk University, Seoul 05029, Republic of Korea. Electronic address:

Biowaste management is a challenging job as it is high in nutrient content and its disposal in open may cause a serious environmental and health risk. Traditional technologies such as landfill, bio-composting, and incineration are used for biowaste management. To gain revenue from biowaste researchers around the world focusing on the integration of biowaste management with other commercial products such as volatile fatty acids (VFA), biohydrogen, and bioplastic (polyhydroxyalkanoates (PHA)), etc. PHA production from various biowastes such as lignocellulosic biomass, municipal waste, waste cooking oils, biodiesel industry waste, and syngas has been reported successfully. Various nutrient factors i.e., carbon and nitrogen source concentration and availability of dissolved oxygen are crucial factors for PHA production. This review is an attempt to summarize the recent advancements in PHA production from various biowaste, its downstream processing, and other challenges that need to overcome making bioplastic an alternate for synthetic plastic.
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http://dx.doi.org/10.1016/j.biortech.2021.124733DOI Listing
April 2021

Bioprospecting of exopolysaccharide from marine Sphingobium yanoikuyae BBL01: Production, characterization, and metal chelation activity.

Bioresour Technol 2021 Mar 7;324:124674. Epub 2021 Jan 7.

Department of Biological Engineering, College of Engineering, Konkuk University, Seoul, Republic of Korea; Institute for Ubiquitous Information Technology and Applications (CBRU), Konkuk University, Seoul, Republic of Korea. Electronic address:

In the present study, an exopolysaccharide (EPS)-producing bacterial strain was isolated from the Eastern Sea (Sokcho Beach) of South Korea and identified as Sphingobium yanoikuyae BBL01. Media optimization was performed using response surface design, and a yield of 2.63 ± 0.02 g/L EPS was achieved. Purified EPS produced using lactose as the main carbon source was analyzed by GC-MS and found to be composed of α-D-xylopyranose (28.6 ± 2.0%), β-D-glucopyranose (21.0 ± 1.6%), α-D-mannopyranose (18.5 ± 1.2%), β-d-mannopyranose (13.1 ± 1.4%), β-D-xylopyranose (10.2 ± 2.1%), α-d-talopyranose (5.9 ± 1.1%), and β-d-galacturonic acid (2.43 ± 0.8%). Interestingly, different carbon sources (glucose, galactose, glycerol, lactose, sucrose, and xylose) showed no effect on EPS monomer composition, with a slight change in the mass percentage of various monosaccharides. Purified EPS was stable up to 233 °C, indicating its possible suitability as a thickening and gelling agent for food-related applications. EPS also showed considerable emulsifying, flocculating, free-radical scavenging, and metal-complexion activity, suggesting various biotechnological applications.
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http://dx.doi.org/10.1016/j.biortech.2021.124674DOI Listing
March 2021

Application of macroalgal biomass derived biochar and bioelectrochemical system with Shewanella for the adsorptive removal and biodegradation of toxic azo dye.

Chemosphere 2021 Feb 5;264(Pt 2):128539. Epub 2020 Oct 5.

Department of Biological Engineering, College of Engineering, Konkuk University, Seoul, 05029, South Korea. Electronic address:

The present study aimed towards adsorptive removal of the toxic azo dye onto biochar derived from Eucheuma spinosum biomass. Characterization of the produced biochar was performed using X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), and Brunauer-Emmett-Teller (BET). Eucheuma spinosum biochar (ES-BC) produced at 600 °C revealed a maximum adsorption capacity of 331.97 mg/g towards reactive red 120 dye. The adsorption data fitted best to the pseudo-second order kinetics (R > 0.99) and Langmuir isotherm (R > 0.98) models. These adsorption models signified the chemisorption mechanism with monolayer coverage of the adsorbent surface with dye molecules. Furthermore, the adsorption process was mainly governed by electrostatic interaction, ion exchange, metal complexation, and hydrogen bonding as supported by the solution pH, FTIR, XPS, and XRD investigation. Nevertheless, alone adsorption technology could not offer a complete solution for eliminating the noxious dyes. Therefore, the bioelectrochemical system (BES) equipped with previously isolated marine Shewanella marisflavi BBL25 was intended for the complete remediation of azo dye. The BES II demonstrated highest dye decolorization (97.06%) within 48 h at biocathode where the reductive cleavage of the azo bond occurred. Cyclic voltammetry (CV) studies of the BES revealed perfect redox reactions taking place where the redox mediators shuttled the electrons to the dye molecule to accelerate the dye decolorization. Besides, the GC-MS analysis revealed biotransformation of the dye into less toxic metabolites as tested using a phyto and cytogenotoxicity.
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http://dx.doi.org/10.1016/j.chemosphere.2020.128539DOI Listing
February 2021

Iron-activated bermudagrass-derived biochar for adsorption of aqueous sulfamethoxazole: Effects of iron impregnation ratio on biochar properties, adsorption, and regeneration.

Sci Total Environ 2021 Jan 13;750:141691. Epub 2020 Aug 13.

Department of Biological and Agricultural Engineering & Texas A&M AgriLife Research Center(,) Texas A&M University, TX 77843, USA; Department of Wildlife, Sustainability, and Ecosystem Sciences, Tarleton State University, TX 76401, USA. Electronic address:

This work focused on the impacts of FeCl impregnation ratio on the properties of FeCl-activated bermudagrass (BG)-derived biochars (IA-BCs), adsorption of sulfamethoxazole (SMX) onto IA-BCs and regeneration of SMX-spent IA-BC. Compared with the control BC (85.82 m/g), IA-BCs made via pyrolysis with FeCl to BG mass ratio between 1 and 3 (1-3 g FeCl/g BG) resulted in significantly enhancing surface area (1014-1035 m/g), hydrophobicity, Fe content in IA-BCs (3.87-7.27%), and graphitized carbon. The properties of IA-BCs supported magnetic separation and higher adsorption (32-265 mg SMX/g BC) than the control BC (6-14 mg SMX/g BC) at various pH. Adsorption experiments indicated various adsorption mechanisms between SMX and IA-BCs via π-π EDA, hydrophobic interactions, and hydrogen bond with intraparticle diffusion limitation. The adsorption was also found to be spontaneous and exothermic. The IA-BC made at FeCl to BG mass ratio of 2 (IA-BC) showed the maximum adsorption capacity for SMX (253 mg SMX/g BC) calculated from Langmuir isotherm model. Additionally, both NaOH desorption and thermal oxidation showed effective regeneration of SMX-saturated IA-BC over multiple cycles. After three cycles of adsorption-regeneration, 64% and 62% of regeneration efficiencies were still achieved under thermal treatment at 300 °C and desorption with 0.1 M NaOH solution, respectively, indicating a cost-efficient adsorbent for the elimination of SMX in water.
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http://dx.doi.org/10.1016/j.scitotenv.2020.141691DOI Listing
January 2021

Facile and Economical Functionalized Hay Biochar with Dairy Effluent for Adsorption of Tetracycline.

ACS Omega 2020 Jul 30;5(27):16521-16529. Epub 2020 Jun 30.

Department of Biological and Agricultural Engineering & Texas A&M AgriLife Research Center, Texas A&M University, 1229 North US Highway 281, Stephenville, Texas 76401, United States.

The present study reports a novel hay biochar functionalized with dairy effluent for enhanced tetracycline (TC) adsorption in the aqueous phase for the first time. The enrichment of hay (i.e., alfalfa) with dairy effluent led to significant accumulation of cationic metals during biochar production. The dairy effluent-functionalized alfalfa biochar (DEAF-BC) possessed strong crystallization (i.e., CaCO), functional groups (i.e., CO, C-O stretching), and high surface area (334 m/g) related to TC adsorption. Therefore, DEAF-BC showed higher TC adsorption capacity (835.7 mg/g) than that of the alfalfa biochar (94.5 mg/g). The adsorption isotherm and kinetic results for the DEAF-BC were correlated with the Freundlich, pseudo-second-order, and intraparticle diffusion models for TC. For the TC adsorption onto DEAF-BC, the thermodynamic analysis implied a spontaneous and endothermic process. Possible mechanisms would include metal complexation, hydrogen bonding, van der Waals forces, and π-π interaction.
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http://dx.doi.org/10.1021/acsomega.0c01099DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7364554PMC
July 2020

Simultaneous monitoring of the bioconversion from lysine to glutaric acid by ethyl chloroformate derivatization and gas chromatography-mass spectrometry.

Anal Biochem 2020 05 16;597:113688. Epub 2020 Mar 16.

Department of Biological Engineering, College of Engineering, Konkuk University, 1 Hwayang-dong, Gwangjin-gu, Seoul, 05029, Republic of Korea. Electronic address:

Glutaric acid is a precursor of a plasticizer that can be used for the production of polyester amides, ester plasticizer, corrosion inhibitor, and others. Glutaric acid can be produced either via bioconversion or chemical synthesis, and some metabolites and intermediates are produced during the reaction. To ensure reaction efficiency, the substrates, intermediates, and products, especially in the bioconversion system, should be closely monitored. Until now, high performance liquid chromatography (HPLC) has generally been used to analyze the glutaric acid-related metabolites, although it demands separate time-consuming derivatization and non-derivatization analyses. To substitute for this unreasonable analytical method, we applied herein a gas chromatography - mass spectrometry (GC-MS) method with ethyl chloroformate (ECF) derivatization to simultaneously monitor the major metabolites. We determined the suitability of GC-MS analysis using defined concentrations of six metabolites (l-lysine, cadaverine, 5-aminovaleric acid, 2-oxoglutaric acid, glutamate, and glutaric acid) and their mass chromatograms, regression equations, regression coefficient values (R), dynamic ranges (mM), and retention times (RT). This method successfully monitored the production process in complex fermentation broth.
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http://dx.doi.org/10.1016/j.ab.2020.113688DOI Listing
May 2020

Adsorptive removal of tetracycline from aqueous solution by maple leaf-derived biochar.

Bioresour Technol 2020 Mar 3;306:123092. Epub 2020 Mar 3.

Department of Biological Engineering, Konkuk University, Seoul 05029, Republic of Korea; The Academy of Applied Science and Technology, Konkuk University, Seoul 05029, Republic of Korea. Electronic address:

The present study evaluates the physicochemical properties of maple leaf-derived biochars (M-BCs) produced at different pyrolytic temperatures (i.e., 350, 550, and 750 °C) and their adsorptive properties for tetracycline onto M-BCs. The increase in pyrolysis temperature to produce M-BCs led to a significant increase in the biochar's hydrophobicity, surface area, and calcite (CaCO) crystallization. The M-BC750 produced without functionalization or activation possessed a high calcite composition and a hydrophobic nature with lower O/C and H/C, hydroxyl groups (-OH) on the surface, and functional groups (i.e., O-containing) as H-bond acceptors. Among M-BCs, the M-BC750 present a highest TC adsorption capacity owing to possible mechanisms such as metal complexation, H-bonding, and hydrophobic interactions. The isotherm and kinetic models for TC adsorption followed the Freundlich models and pseudo-second-order models, respectively. M-BCs produced from the waste fallen maple leaves could be applied as low-cost environmental adsorbents for TC removal.
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http://dx.doi.org/10.1016/j.biortech.2020.123092DOI Listing
March 2020

Conversion of waste cooking oil into biodiesel using heterogenous catalyst derived from cork biochar.

Bioresour Technol 2020 Apr 23;302:122872. Epub 2020 Jan 23.

Department of Biological Engineering, College of Engineering, Konkuk University, Seoul, South Korea; Institute for Ubiquitous Information Technology and Applications (CBRU), Konkuk University, Seoul, South Korea. Electronic address:

In this study, a heterogeneous catalyst prepared by pyrolysis of waste cork (Quercus suber) was used for the transesterification of waste cooking oil (WCO). Physicochemical properties of the synthesized biochar catalyst were studied using BET, SEM, FTIR, and XRD. The experiment results demonstrate that heterogeneous catalyst synthesized at 600 °C showed maximum fatty acids methyl esters (FAMEs) conversion (98%) at alcohol:oil (25:1), catalyst loading (1.5% w/v) and temperature 65 °C. Biodiesel produced from WCO (Canola oil) mainly composed of FAMEs in following order C18:1 > C18:2 > C16:0 > C18:0 > C20:0. Properties of produced biodiesel were analysed as cetane number (CN) 50.56, higher heating value (HHV) 39.5, kinematic viscosity (ʋ) 3.9, and density (ρ) 0.87.
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http://dx.doi.org/10.1016/j.biortech.2020.122872DOI Listing
April 2020

Adsorption behavior of tetracycline onto Spirulina sp. (microalgae)-derived biochars produced at different temperatures.

Sci Total Environ 2020 Mar 26;710:136282. Epub 2019 Dec 26.

Department of Biological Engineering, Konkuk University, Seoul 05029, Republic of Korea. Electronic address:

We evaluated the production of Spirulina sp. (microalgae)-derived biochars (SPAL-BCs) at different pyrolysis temperatures for the removal of an emerging water contaminant, tetracycline (TC). Physicochemical properties of SPAL-BCs were characterized and related with their capacity to adsorb TC. Increasing pyrolysis temperatures led to higher aromaticity, higher hydrophobicity, and higher specific surface area. In particular, SPAL-BC750 possessed the highest hydrophobicity, various strong crystallizations (i.e., calcite, hydroxyapatite, and rhenanite) and functional groups (i.e., CH, CN, CO, and CO), which may be associated with high TC adsorption. SPAL-BC750 also presented the highest TC adsorption capacity (132.8 mg TC/g biochar) via batch experimentation because of hydrophobic, π-π interactions, functional groups, and metal complexation. The best fitting isotherm and kinetic models of TC adsorption by SPAL-BC750 were the Langmuir and pseudo-first order models, respectively. SPAL-BCs obtained as a by-product of pyrolysis may be an economical and potentially valuable adsorbent for aqueous antibiotic removal.
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http://dx.doi.org/10.1016/j.scitotenv.2019.136282DOI Listing
March 2020

Treatment of furazolidone contaminated water using banana pseudostem biochar engineered with facile synthesized magnetic nanocomposites.

Bioresour Technol 2020 Feb 21;297:122472. Epub 2019 Nov 21.

Department of Biological Engineering, College of Engineering, Konkuk University, Seoul 05029, Republic of Korea; Institute for Ubiquitous Information Technology and Applications (CBRU), Konkuk University, Seoul 05029, Republic of Korea. Electronic address:

The present study enlightens facile synthesis and characterization of magnetic biochar derived from waste banana pseudostem biomass for the removal of nitrofuran antibiotic 'furazolidone' (FZD). Brunauer-Emmett-Teller (BET), scanning electron microscopy (SEM), magnetic hysteresis, X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR) revealed successful hybridization of magnetic nanocomposites with biochar (BPB). The maximum adsorption capacity of magnetic BPB was 96.81% (37.86 mg g), which was significantly higher than the non-coated BPB (77.25%; 31.45 mg g). Adsorption kinetics data fitted well with pseudo-second order, and Elovich model demonstrating dominance of the chemisorption mechanism. Furthermore, the response surface methodology (RSM) was applied to evaluate the interactive effect of pH, temperature, and FZD concentration on adsorption. Therefore, the results of present study would provide an effective strategy to tackle antibiotic contaminants responsible for the antibiotic resistance genes or bacteria that decreases the therapeutic value of antibiotics.
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http://dx.doi.org/10.1016/j.biortech.2019.122472DOI Listing
February 2020

Polyhydroxybutyrate production in halophilic marine bacteria Vibrio proteolyticus isolated from the Korean peninsula.

Bioprocess Biosyst Eng 2019 Apr 7;42(4):603-610. Epub 2019 Jan 7.

Department of Biological Engineering, College of Engineering, Konkuk University, 1 Hwayang-dong, Gwangjin-gu, Seoul, 05029, Republic of Korea.

Polyhydroxybutyrates (PHB) are biodegradable polymers that are produced by various microbes, including Ralstonia, Pseudomonas, and Bacillus species. In this study, a Vibrio proteolyticus strain, which produces a high level of polyhydroxyalkanoate (PHA), was isolated from the Korean marine environment. To determine optimal growth and production conditions, environments with different salinity, carbon sources, and nitrogen sources were evaluated. We found that the use of a medium containing 2% (w/v) fructose, 0.3% (w/v) yeast extract, and 5% (w/v) sodium chloride (NaCl) in M9 minimal medium resulted in high PHA content (54.7%) and biomass (4.94 g/L) over 48 h. Addition of propionate resulted in the production of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (P(HB-co-HV)) copolymer as propionate acts as a precursor for the HV unit. In these conditions, the bacteria produced poly(3-hydroxybutyrate-co-3-hydroxyvalerate) containing a 15.8% 3HV fraction with 0.3% propionate added as the substrate. To examine the possibility of using unsterilized media with high NaCl content for PHB production, V. proteolyticus was cultured in sterilized and unsterilized conditions. Our results indicated a higher growth, leading to a dominant population in unsterilized conditions and higher PHB production. This study showed the conditions for halophilic PHA producers to be later implemented at a larger scale.
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http://dx.doi.org/10.1007/s00449-018-02066-6DOI Listing
April 2019

Effects of pyrolysis temperature on the physicochemical properties of alfalfa-derived biochar for the adsorption of bisphenol A and sulfamethoxazole in water.

Chemosphere 2019 Mar 24;218:741-748. Epub 2018 Nov 24.

Department of Agricultural and Biological Engineering & Texas A&M AgriLife Research Center at Stephenville, Texas A&M University, USA; Department of Wildlife, Sustainability, and Ecosystem Sciences, Tarleton State University, USA. Electronic address:

The present study reports alfalfa (one of most abundant hays in U.S)-derived biochar for effective removal of emerging contaminants in water for the first time. The physicochemical properties of alfalfa-derived biochar (AF-BC) made at various pyrolysis temperatures were investigated, and correlated with the adsorption of bisphenol A (BPA) and sulfamethoxazole (SMX) in water. The increase in pyrolysis temperatures from 350 °C to 650 °C for the pyrolysis of AF led to a drastic increase in surface area and carbonization with the loss of functional groups. The AF-derived biochar made at 650 °C showed much higher adsorption capacities for BPA and SMX than those made at 350-550 °C, mainly owing to the hydrophobic and π-π interactions supported by its high surface area and degree of carbonization. The adsorption isotherms fitted the Freundlich for BPA and Temkin models for SMX well, respectively. The adsorption capacities of AF 650 for BPA and SMX were higher than those of other biochars but lower than those of commercial activated carbon. The pH-dependent desorption for AF 650 showed high efficiency for SMX, but low efficiency for BPA indicating needs for alternative regeneration methods for BPA.
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http://dx.doi.org/10.1016/j.chemosphere.2018.11.151DOI Listing
March 2019

Biotechnological potential of microbial consortia and future perspectives.

Crit Rev Biotechnol 2018 Dec 15;38(8):1209-1229. Epub 2018 May 15.

a Department of Biological Engineering, College of Engineering , Konkuk University , Seoul , South Korea.

Design of a microbial consortium is a newly emerging field that enables researchers to extend the frontiers of biotechnology from a pure culture to mixed cultures. A microbial consortium enables microbes to use a broad range of carbon sources. It provides microbes with robustness in response to environmental stress factors. Microbes in a consortium can perform complex functions that are impossible for a single organism. With advancement of technology, it is now possible to understand microbial interaction mechanism and construct consortia. Microbial consortia can be classified in terms of their construction, modes of interaction, and functions. Here we discuss different trends in the study of microbial functions and interactions, including single-cell genomics (SCG), microfluidics, fluorescent imaging, and membrane separation. Community profile studies using polymerase chain-reaction denaturing gradient gel electrophoresis (PCR-DGGE), amplified ribosomal DNA restriction analysis (ARDRA), and terminal restriction fragment-length polymorphism (T-RFLP) are also reviewed. We also provide a few examples of their possible applications in areas of biopolymers, bioenergy, biochemicals, and bioremediation.
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http://dx.doi.org/10.1080/07388551.2018.1471445DOI Listing
December 2018

Adsorption isotherm, kinetic modeling and mechanism of tetracycline on Pinus taeda-derived activated biochar.

Bioresour Technol 2018 Jul 6;259:24-31. Epub 2018 Mar 6.

Texas A&M AgriLife Research Center, 1229 North US Highway 281, Stephenville, TX 76401, USA; Office of Sponsored Projects, Tarleton State University, 1333 W. Washington, Stephenville, TX 76401, USA. Electronic address:

The objective of this study was to evaluate the adsorption of tetracycline (TC) on the Pinus taeda-derived activated biochar (BC). After NaOH activation, the well-developed porous surface structure was observed with a significantly increase in surface area (959.9 m/g). The kinetic and isotherm studies indicated that hydrogen bonding and π-π interaction on the heterogeneous surface would be the possible mechanisms, while intra-particle diffusion was considered as the major limitation for the adsorption of TC on the activated BC. The maximum adsorption capacity of the activated BC (274.8 mg TC/g BC) was higher than those of various activated BCs from the previous studies while it was similar to those of commercial activated carbons. It indicated that the activated BC had the high potential for TC removal in water.
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http://dx.doi.org/10.1016/j.biortech.2018.03.013DOI Listing
July 2018

Effects of dairy manure-derived biochar on psychrophilic, mesophilic and thermophilic anaerobic digestions of dairy manure.

Bioresour Technol 2018 Feb 27;250:927-931. Epub 2017 Nov 27.

Texas A&M AgriLife Research Center, 1229 North US Highway 281, Stephenville, TX 76401, USA; Office of Sponsored Projects, Tarleton State University, 1333 W. Washington, Stephenville, TX 76401, USA. Electronic address:

Effects of dairy manure-derived biochar (M-BC) on methane production in anaerobic digestion (AD) of dry dairy manure were investigated with three different concentrations of biochar (0, 1 and 10 g/L) and temperatures (psychrophilic, 20 °C; mesophilic, 35 °C; thermophilic, 55 °C). Compared with the AD without any biochar, the cumulative methane and yield in the AD with 10 g/L biochar were increased to 27.65% and 26.47% in psychrophilic, 32.21% and 24.90% in mesophilic and 35.71% and 24.69% in thermophilic digestions. The addition of M-BC shortened the lag phases of AD at all temperatures in the study while it lowered the concentration of total VFAs and propionic acid. It was suggested that the high nutrients and alkalinity potential of M-BC (i.e. 9.1% Ca, 3.6% Mg, 1.3% N, 0.14% P) would play significant roles in enhancing methane production and shortening lag phases from the AD of dairy manure.
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http://dx.doi.org/10.1016/j.biortech.2017.11.074DOI Listing
February 2018

L-Glycine Alleviates Furfural-Induced Growth Inhibition during Isobutanol Production in Escherichia coli.

J Microbiol Biotechnol 2017 Dec;27(12):2165-2172

Department of Biological Engineering, College of Engineering, Konkuk University, Seoul 05029, Republic of Korea.

Lignocellulose is now a promising raw material for biofuel production. However, the lignin complex and crystalline cellulose require pretreatment steps for breakdown of the crystalline structure of cellulose for the generation of fermentable sugars. Moreover, several fermentation inhibitors are generated with sugar compounds, majorly furfural. The mitigation of these inhibitors is required for the further fermentation steps to proceed. Amino acids were investigated on furfural-induced growth inhibition in producing isobutanol. Glycine and serine were the most effective compounds against furfural. In minimal media, glycine conferred tolerance against furfural. From the IC₅₀ value for inhibitors in the production media, only glycine could alleviate growth arrest for furfural, where 6 mM glycine addition led to a slight increase in growth rate and isobutanol production from 2.6 to 2.8 g/l under furfural stress. Overexpression of glycine pathway genes did not lead to alleviation. However, addition of glycine to engineered strains blocked the growth arrest and increased the isobutanol production about 2.3-fold.
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http://dx.doi.org/10.4014/jmb.1705.05020DOI Listing
December 2017

Biotransformation of pyridoxal 5'-phosphate from pyridoxal by pyridoxal kinase (pdxY) to support cadaverine production in Escherichia coli.

Enzyme Microb Technol 2017 Sep 13;104:9-15. Epub 2017 May 13.

Department of Biological Engineering, College of Engineering, Konkuk University, 1 Hwayang-dong, Gwangjin-gu, Seoul, 05029, Republic of Korea; Institute for Ubiquitous Information Technology and Applications (CBRU), Konkuk University, Seoul 143-701, Republic of Korea. Electronic address:

Cadaverine, a five-carbon diamine (1,5-diaminopentane), can be made by fermentation or direct bioconversion and plays an important role as a building block of polyamides. Lysine decarboxylase (CadA) transforms L-lysine to cadaverine and pyridoxal 5'-phosphate (PLP) can increases conversion rate and yield as a cofactor. Biotransformation of cadaverine using whole Escherichia coli cells that overexpress the lysine decarboxylase has many merits, such as the rapid conversion of l-lysine to cadaverine, possible application of high concentration reactions up to the molar level, production of less byproduct and potential reuse of the enzyme by immobilization. However, the supply of PLP, which is a cofactor of lysine decarboxylase, is the major bottleneck in this system. Therefore, we initiated our study on PLP precursors and PLP-related enzymes and discovered that pyridoxal (PL) can be a viable alternative to supply PLP. Among various PLP systems examined, pyridoxal kinase (PdxY) showed the highest conversion of PL to PLP, resulting in more than 60% conversion of l-lysine to cadaverine with lysine decarboxylase. When the reaction with 0.4M l-lysine, 0.2mM PL and more whole cells was performed, it resulted in an 80% conversion yield. Furthermore, when barium-alginate immobilization was applied, it showed a 90% conversion yield in 1h with PL, suggesting that it is compatible with developed whole-cell systems without a direct supply of exogenous PLP.
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http://dx.doi.org/10.1016/j.enzmictec.2017.05.002DOI Listing
September 2017

Enhanced growth and total fatty acid production of microalgae under various lighting conditions induced by flashing light.

Eng Life Sci 2017 Sep 18;17(9):976-980. Epub 2017 Apr 18.

Department of Biological Engineering Konkuk University Seoul Republic of Korea.

Microalgae are gaining importance as a source of high-value bioproducts. However, data regarding optimization of algal productivity via variation of environmental factors are lacking. Here, we evaluated a novel lighting method for the enhancement of biomass and total fatty acid (TFA) productivities during algal cultivation. We cultivated six different algal strains ( KCTC AG10002, KGE18, sp. KGE03, KGE19, sp., and sp.) under various lighting conditions-continuous light (CL), light-dark cycle (LD), and continuous dark (CD)-with or without additional flashing light. We monitored dry cell weight (DCW) and TFA concentrations during cultivation. For each algal strain, the growth rate showed markedly different responses to the various lighting modes. The growth rates of KCTC AG10002 (1.34-fold DCW increase, LD with flash), . KGE18 (5.16-fold DCW increase, LD with flash), sp. KGE03 (2.77-fold DCW increase, CL with flash), and . KGE19 (1.52-fold DCW increase, CL with flash) markedly increased in response to flashing light. Additionally, in some algal strains cultivated under the LD mode, the flashing light treatment induced increased TFA concentrations (. , 1.19-fold increase; . , 2.59-fold increase; and . , 3.31-fold increase). Phytohormone analysis of . revealed increases in growth rate and TFA concentrations, associated with phytohormone induction via flashing light (e.g. 2.93-fold increase in gibberellic acid); hence, flashing light can promote substantial alterations in algal metabolism.
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http://dx.doi.org/10.1002/elsc.201700001DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6999561PMC
September 2017

Cytotoxic Effects of ZnO Nanoparticles on the Expression of ROS-Responsive Genes in the Human Cell Lines.

J Nanosci Nanotechnol 2016 Jan;16(1):210-8

In the present investigation, engineered ZnO nanoparticles were tested for their induced oxidative stress in T47D tumor cell lines. The expressions of reactive oxygen species (ROS) related genes, glutathione S-transferase (GST) and catalase were quantified by real time-polymerase chain reaction (RT-PCR). In addition, qualitative analysis of GST was also performed at the cell level using molecular beacon (MB) technology. The tested nanoparticles were 20 nm in size, water-dispersible and treated on human breast tumor epithelial cell lines at 20, 40, 80 µg/ml concentration with 14, 28, 48 h incubation times. Nanoparticles induced expressions of ROS responsive genes at molecular and cellular level, produces consistent results with respect to different dosage and incubation time. The experiment showed that the expression of both GST and catalase genes were maximized at 28 h with 80 µg/ml concentration. However, the toxic effect of the monodisperse ZnO nanoparticles was not significant compared with control experiments, demonstrating its high potential in the applications of nanomedicines for a diagnostic and therapeutic tool.
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http://dx.doi.org/10.1166/jnn.2016.10746DOI Listing
January 2016

In vitro cytotoxic evaluation of MgO nanoparticles and their effect on the expression of ROS genes.

Int J Mol Sci 2015 Apr 3;16(4):7551-64. Epub 2015 Apr 3.

Department of Biological Engineering, Konkuk University, 120 Neungdong-ro, Gwangjin-Gu, Seoul 143701, Korea.

Water-dispersible MgO nanoparticles were tested to investigate their cytotoxic effects on oxidative stress gene expression. In this in vitro study, genes related to reactive oxygen species (ROS), glutathione S-transferase (GST) and catalase, were quantified using real-time polymerase chain reactions (molecular level) and molecular beacon technologies (cellular level). The monodispersed MgO nanoparticles, 20 nm in size, were used to treat human cancer cell lines (liver cancer epithelial cells) at different concentrations (25, 75 and 150 µg/mL) and incubation times (24, 48 and 72 h). Both the genetic and cellular cytotoxic screening methods produced consistent results, showing that GST and catalase ROS gene expression was maximized at 150 µg/mL nanoparticle treatment with 48 h incubation. However, the genotoxic effect of MgO nanoparticles was not significant compared with control experiments, which indicates its significant potential applications in nanomedicine as a diagnostic and therapeutic tool.
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http://dx.doi.org/10.3390/ijms16047551DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4425033PMC
April 2015

LED light stress induced biomass and fatty acid production in microalgal biosystem, Acutodesmus obliquus.

Spectrochim Acta A Mol Biomol Spectrosc 2015 Jun 9;145:245-253. Epub 2015 Mar 9.

Department of Biological Engineering, Konkuk University, 120 Neungdong-ro, Gwangjin-Gu, Seoul 143-701, Republic of Korea.

Microbial algal system can serve as a potential source for the production of much high value bioproducts and biofuels. The quality and intensity of light are the key elements to optimize the production of algal biomass and fatty acid contents. This study presents the effect of differential LED flashing light conditions on the growth of microalgae, Acutodesmus obliquus. The induced light stress was optimized for its biomass and fatty acid content. The microalgae are exposed to various frequency of intermittent LED flashing light (blue and red lights) at three different phases in the 18 day cell growth (log, lag and stationary phase). The frequency of light flashing rate was adjusted to 120, 10, 5, 3.75, and 1 times per min. The effect of light stress on growth and fatty acids composition of A. obliquus induced an increase in algae growth and fatty acid production. Different optimal timing for light stress was subjected to elucidate the effect of light stress on algae growth and fatty acid production. The results showed an increase in the algae growth (1.2mg/L of chl a content) under light stress condition at FT10 (flashing time, 10 times per min) from the initial day (log phase) compared with the control experiment (0.4 mg/L of chl a content). However, the total fatty acids (71 mg/g) and volumetric FAME production (9.4 ml/l) level was found to be significant under FT5 (flashing time, 5 times per min), adopting flashing light from day 10 (stationary phase). TEM studies also revealed the deposition of lipid to be largest in the 18 day old cells under flashing light (FT5) condition, representing maximum accumulation of lipids bodies (up to 770 nm diameter in particle size) occupying approximately 42% of the total area of the cell.
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http://dx.doi.org/10.1016/j.saa.2015.03.035DOI Listing
June 2015

Quantitation of oxidative stress gene expression in MCF-7 human cell lines treated with water-dispersible CuO nanoparticles.

Appl Biochem Biotechnol 2014 Jun 5;173(3):731-40. Epub 2014 Apr 5.

Department of Biological Engineering, Konkuk University, 120 Neungdong-ro, Gwangjin-Gu, Seoul, 143701, Republic of Korea,

The objective of this study was to assess the cytotoxicity of water-dispersible CuO nanoparticles by quantifying the reactive oxygen species (ROS)-related genes (glutathione S-transferase (GST) and catalase) using real-time polymerase chain reaction (RT-PCR). Monodisperse CuO nanoparticles of 14 nm in size were used. Cytotoxicity of CuO nanoparticles was evaluated under in vitro condition at different concentrations (10, 50, and 100 μg/ml) and incubation times (12, 24, and 48 h) with human cancer cell lines (breast cancer epithelial cells). The genetic level cytotoxic screening produced consistent results showing that GST and catalase ROS gene expression was maximized in 24 h incubation at 100 μg/ml concentration of CuO nanoparticles. However, the cytotoxicity of water-dispersible CuO nanoparticle was not significant compared with control experiments, demonstrating its high potential in the application of nanomedicines for a diagnostic and therapeutic tool.
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http://dx.doi.org/10.1007/s12010-014-0875-5DOI Listing
June 2014

Identification and functional characterization of an α-amylase with broad temperature and pH stability from Paenibacillus sp.

Appl Biochem Biotechnol 2013 May 26;170(2):359-69. Epub 2013 Mar 26.

Department of Microbial Engineering, College of Engineering, Konkuk University, 1 Hwayang-dong, Gwangjin-gu, Seoul, 143-701, Korea.

Amylases are important industrial enzymes that have been applied widely in the food, detergent, and pulp industries and fermentation processes. In the present study, a gene encoding an alpha-amylase from the genomic DNA library of Paenibacillus sp. was identified and characterized. The amylase gene designated amy1 was shown to consist of 1,980 bp and shared sequence identity towards α-amylase genes from other Bacillus sp. The deduced amino acid sequence for Amy1 indicated 80 % sequence identity with other Bacillus strains. Heterologous expression of recombinant Amy1 in Escherichia coli BL21(DE3) facilitated the recovery of this protein in soluble form. Enzyme kinetic data revealed Amy1 to have a K m of 23.83 mg/mL and K cat of 48.74 min(-1) and K cat /K m of 2 min(-1) mg(-1) mL(-1) for starch. The activity of this protein was found to be enhanced by Mn(2+), and furthermore, Amy1 remained active at a broad pH range (4-10) and temperature (30-90 °C). The ability of Amy1 to act on food waste under broad temperature and pH conditions, together with its ability to produce simple sugars, shows many advantages for further application in the food industry.
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http://dx.doi.org/10.1007/s12010-013-0197-zDOI Listing
May 2013

Glucose oxidase/cellulose-carbon nanotube composite paper as a biocompatible bioelectrode for biofuel cells.

Appl Biochem Biotechnol 2013 Nov 19;171(5):1194-202. Epub 2013 Mar 19.

Department of Chemical and Biochemical Engineering, Dongguk University-Seoul, 30 Pildong-ro 1-gil, Jung-gu, Seoul, 100-715, Republic of Korea.

Biofuel cells are devices for generating electrical energy directly from chemical energy of renewable biomass using biocatalysts such as enzymes. Efficient electrical communication between redox enzymes and electrodes is essential for enzymatic biofuel cells. Carbon nanotubes (CNTs) have been recognized as ideal electrode materials because of their high electrical conductivity, large surface area, and inertness. Electrodes consisting entirely of CNTs, which are known as CNT paper, have high surface areas but are typically weak in mechanical strength. In this study, cellulose (CL)-CNT composite paper was fabricated as electrodes for enzymatic biofuel cells. This composite electrode was prepared by vacuum filtration of CNTs followed by reconstitution of cellulose dissolved in ionic liquid, 1-ethyl-3-methylimidazolium acetate. Glucose oxidase (GOx), which is a redox enzyme capable of oxidizing glucose as a renewable fuel using oxygen, was immobilized on the CL-CNT composite paper. Cyclic voltammograms revealed that the GOx/CL-CNT paper electrode showed a pair of well-defined peaks, which agreed well with that of FAD/FADH2, the redox center of GOx. This result clearly shows that the direct electron transfer (DET) between the GOx and the composite electrode was achieved. However, this DET was dependent on the type of CNTs. It was also found that the GOx immobilized on the composite electrode retained catalytic activity for the oxidation of glucose.
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http://dx.doi.org/10.1007/s12010-013-0188-0DOI Listing
November 2013

Ionic liquid-mediated extraction of lipids from algal biomass.

Bioresour Technol 2012 Apr 1;109:312-5. Epub 2011 May 1.

Department of Microbial Engineering, Konkuk University, Seoul 143-701, South Korea.

Lipids from algal biomass were extracted using mixtures of ionic liquids (ILs) and methanol, and fatty acid profiles of the extracted lipids were characterized in this work. Mixtures of ILs and methanol successfully dissolved biomass leaving lipids insoluble. The total contents of lipids extracted from commercial and cultivated Chlorella vulgaris were 10.6% and 11.1%, respectively, by the conventional Bligh and Dyer's method, while a mixture of [Bmim][CF(3)SO(3)] and methanol extracted 12.5% and 19.0% of the lipids, respectively. Multi-parameter regression by the linear solvation energy relationship showed that dipolarity/polarizability and hydrogen bond acidity of ILs are more important than their hydrogen bond basicity for effectively extracting lipids from algal biomass. Fatty acid profiles of the lipids extracted using IL-methanol mixtures showed that C16:0, C16:1, C18:2, and C18:3 fatty acids were dominant. This suggests that the lipids extracted from C. vulgaris can be used as a source of biodiesel production.
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http://dx.doi.org/10.1016/j.biortech.2011.04.064DOI Listing
April 2012