A Hurdle Technology of Slightly Acidic Electrolyzed Water for Establishment of Microbial Safety and Shelf Life Extension of Fresh-cut Bell Pepper

Ke Luo,Deog-Hwan Oh 한국식품영양과학회 2015 한국식품영양과학회 학술대회발표집 Vol.2015 No.8

Development of Predictive Models for the Growth Kinetics of Listeria monocytogenes on Fresh Pork under Different Storage Temperatures

Ke Luo,Won Hyung Choi,Joong Hyun Park,Fereidoun Forghan,Charles Nkufi Tango,Shuai Wei,Ahmad Rois Mansur,Deog Hwan Oh 한국식품영양과학회 2014 한국식품영양과학회 학술대회발표집 Vol.2014 No.10

Self-assembly kinetics of debranched short-chain glucans from waxy maize starch to form spherical microparticles and its applications

Luo, Ke,Park, Kyu-Hwan,Lee, Da-Hee,Hong, Chae-Eun,Song, Young-Woon,Yoo, Sang-Ho,Kim, Young-Rok Elsevier 2019 Colloids and surfaces Biointerfaces Vol.176 No.-

<P><B>Abstract</B></P> <P>Starch microparticles (SMPs) of well-defined size and morphology were synthesized through pullulanase-mediated debranching of waxy maize starch followed by spontaneous re-assembly of the resulting short-chain glucan molecules in aqueous solution. Enzymatic debranching of amylopectins from native starch generated two major fractions corresponding to a smaller glucan and partially digested larger amylopectin molecules. The ratio of short-chain glucan (SCG) over partially digested amylopectin (PDAp) turned out to be the deterministic factors for the size and crystallinity of SMPs, of which the ratio could be controlled by the concentration of debranching enzyme. The PDAp fraction was closely associated with the creation of nuclei, determining the growth kinetics of SMPs which led to the formation of SMPs with a diameter ranging from 0.52.5 μm. In addition, we demonstrated that iron oxide nanoparticles (IONPs) were successfully incorporated into the starch microstructure by introducing them during the self-assembly reaction, conferring desired functionality onto the final SMPs. The incorporated IONPs rendered the SMPs an excellent magnetic sensitivity, which were successfully applied for the separation and concentration of target bacteria upon conjugation of specific antibody on the surface of SMPs. The simple processes and biocompatible nature of starch would make this approach attractive for many applications in the area of food, medicine and other related materials sciences.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Well-defined starch microparticles (SMPs) were synthesized from waxy maize starch. </LI> <LI> Debranching of amylopectin followed by self-assembly led to the formation of SMPs. </LI> <LI> Nucleation and growth kinetics of SMPs were investigated. </LI> <LI> The ratio of short-chain glucan is the key to determine the size of SMPs. </LI> <LI> Their potential as an effective immunomagnetic materials was demonstrated. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Fabrication of well-defined starch-based immunomagnetic microparticles

Ke Luo,Ki-Baek Jeong,Jun-Hee Lee,Young-Rok Kim 한국산업식품공학회 2017 학술대회 및 심포지엄 Vol.2017 No.04

Amylose is carbohydrate polymer defined as a linear natural polysaccharide composed of α(1→4) bound glucose units. Due to its abundance, renewable nature, low cost, and biodegradability, this polymer is regarded as a promising green material for producing crystals and particles of different sizes ranging from the nanometer scale to the micrometer scale. Herein, short amylose chains and dextran-coated iron oxide magnetic nanoparticles (Dex@MNPs) were introduced to fabricate individual superparamagnetic amylose microparticles (SAMPs), which have a well-defined spherical shape and a uniform size of about 1 μm. We found that the aggregation of SAMPs can be mediated by the introduced Dex@MNPs in a concentration-dependent manner, indicating that Dex@MNPs, as the seed crystals, play an important role in self-assembly of SAMPs. By using streptococcal protein G tagged with maltose binding protein (MBP-SPG), specific antibody against Escherichia coli O157:H7 was successfully immobilized on the surface of SAMPs. The Ab-functionalized SAMPs showed a high capture efficiency (>90%) comparable to the commercial immunomagnetic microparticles regardless of suspending agents (1X PBS and milk). Moreover, SAMPs exhibited excellent recyclability, in which the Ab immobilized on the surface of SAMPs can be refreshed by using the maltose elution buffer along with the unchanged capture efficiency. In addition, SAMPs were assembled into the linear rod-shape microstructure by the introduced magnetic field during the amylose-mediated precipitation process. The convenient self-assembly of SAMPs with the well-defined size and shape, biocompatibility, tolerance to environmental variances, high magnetic response behavior, and excellent recyclability in the functionalization make these magnetic microparticles promising for many potential applications such as bio-sensing, labeling, and smart delivery of active compounds.

Polymorphisms in DNA Repair Genes and Risk of Glioma and Meningioma

Luo, Ke-Qin,Mu, Shi-Qing,Wu, Zhong-Xue,Shi, Yi-Ni,Peng, Ji-Cai Asian Pacific Journal of Cancer Prevention 2013 Asian Pacific journal of cancer prevention Vol.14 No.1

Polymorphisms in DNA repair genes have been shown to influence DNA repair processes and to modify cancer susceptibility. Here we conducted a case-control study to assess the role of potential SNPs of DNA repair genes on the risk of glioma and meningioma. We included 297 cases and 458 cancer-free controls. Genotyping of XRCC1 Gln399Arg, XRCC1 Arg194Trp, XRCC2 Arg188His, XRCC3 Thr241Met, XRCC4 Ala247Ser, ERCC1 Asn118Asp, ERCC2 Lys751Gln and ERCC5 Asp1558His were performed in a 384-well plate format on the Sequenom MassARRAY platform. XRCC1 Arg194Trp (rs1799782) and ERCC2 Asp312Asn rs1799793 did not follow the HWE in control group, and genotype distributions of XRCC1 Gln399Arg rs25487, XRCC2 Arg188His rs3218536 and ERCC2 Asp312Asn rs1799793 were significantly different between cases and controls (P<0.05). We found XRCC1 399G/G, XRCC1 194 T/T and XRCC3 241T/T were associated with a higher risk when compared with the wild-type genotype. For ERCC5 Asp1558His, we found G/G genotype was associated with elevated susceptibility. In conclusion, our study has shown that XRCC1 Gln399Arg, XRCC1 Arg194Trp, XRCC3 Thr241Met and ERCC5 Asp1558His are associated with risk of gliomas and meningiomas. This finding could be useful in identifying the susceptibility genes for these cancers.

Synergistic Effect of Slightly Acidic Electrolyzed Water and Ultrasound at Mild Heat Temperature in Microbial Reduction and Shelf-Life Extension of Fresh-Cut Bell Pepper

( Ke Luo ),( Deog Hwan Oh ) 한국미생물 · 생명공학회 2015 Journal of microbiology and biotechnology Vol.25 No.9

The objectives of this study were to evaluate the effect of combined treatments (slightly acidic electrolyzed water (SAEW), ultrasound (US), or mild heat (60°C)) on the growth of Listeria monocytogenes and Salmonella enterica serovar Typhimurium in fresh-cut bell pepper, and the shelf-life and sensory quality (color and texture) were followed during storage at 4ºC and 25°C. An additional 0.65, 1.72, and 2.70 log CFU/g reduction was achieved by heat treatments at 60°C for 1 min for DW, SAEW, and SAEW+US, respectively. Regardless of the type of pathogen, the combined treatment (SAEW+US+60°C) achieved a significantly (p < 0.05) longer lag time in all treatment groups. This combined treatment also prolonged the shelf-life of bell pepper up to 8 days and 30 h for the storage at 4ºC and 25ºC, respectively. There was also no significant difference in the color and hardness of treated (SAEW+US+60°C) bell pepper from that of control during the storage. This new hurdle approach is thus expected to improve the microbial safety of bell peppers during storage and distribution.

Biosynthesis of well-defined starch magnetic microbeads

Ke Luo,Ki-Baek Jeong,Sang-Mook You,Young-Rok Kim 한국산업식품공학회 2018 학술대회 및 심포지엄 Vol.2018 No.04

Amylose is carbohydrate polymer defined as a linear natural polysaccharide composed of α(1→4) bound glucose units. Due to its abundance, renewable nature, low cost, and biodegradability, this polymer is regarded as a promising green material for producing crystals and particles of different sizes ranging from the nanometer scale to the micrometer scale. Herein, short amylose chains and dextran-coated iron oxide magnetic nanoparticles (Dex@IONPs) were introduced to fabricate well-dispersed starch magnetic microbeads (SMMBs), which have a well-defined spherical shape and a uniform size of about 1 μm. We found that the aggregation of SMMBs can be mediated by the introduced Dex@IONPs in a concentration-dependent manner, indicating that Dex@MNPs, as the seed crystals, play an important role in self-assembly of SMMBSs. By using streptococcal protein G tagged with maltose binding protein (MBP-SPG), specific antibody against Escherichia coli O157:H7 was successfully immobilized on the surface of SMMBs. The Ab-functionalized SMMBs showed a high capture efficiency (>90%) comparable to the commercial immunomagnetic microparticles regardless of suspending agents (1X PBS and milk). Moreover, SMMBs exhibited excellent recyclability, in which the Ab immobilized on the surface of SMMBs can be refreshed by using the maltose elution buffer along with the unchanged capture efficiency. In addition, SMMBSs were assembled into the linear rod-shape microstructure by the introduced magnetic field during the amylose-mediated precipitation process. The convenient self-assembly of SMMBs with the well-defined size and shape, biocompatibility, tolerance to environmental variances, high magnetic response behavior, and excellent recyclability in the functionalization make these magnetic microparticles promising for many potential applications such as bio-sensing, labeling, and smart delivery of active compounds.

Molecular Rearrangement of Glucans from Natural Starch To Form Size-Controlled Functional Magnetic Polymer Beads

Luo, Ke,Jeong, Ki-Baek,You, Sang-Mook,Lee, Da-Hee,Kim, Young-Rok American Chemical Society, Books and Journals Divi 2018 Journal of agricultural and food chemistry Vol.66 No.26

<P>Herein, we report a fairly simple and environmentally friendly approach for the fabrication of starch-based magnetic polymer beads (SMPBs) with uniform shape and size through spontaneous rearrangement of short-chain glucan (SCG) produced by enzymatic debranching of waxy maize starch. The paramagnetic materials, dextran-coated iron oxide nanoparticles (Dex@IONPs), were readily incorporated into the starch microstructure and rendered a superparamagnetic property to the SMPBs. The morphology and size of resulting SMPBs turned out to be modulated by Dex@IONPs in a concentration-dependent manner, of which Dex@IONPs was assumed to be acting as a seed inducing the epitaxial crystallization of SCG and further transforming it into homogeneous microparticles. The surface of SMPBs was readily functionalized with an antibody through a one-step reaction using a linker protein. The immuno-SMPBs showed great capture efficiency (>90%) for target bacteria. The colloidal stability and favorable surface environment for biomolecules are believed to be responsible for the high capture efficiency and specificity of the SMPBs. Furthermore, the captured bacteria along with antibody and linker protein were effectively eluted from the surface of SMPBs by adding free maltose, making this new material suitable for various chromatographic applications.</P> [FIG OMISSION]</BR>

A combined hurdle approach of slightly acidic electrolyzed water simultaneous with ultrasound to inactivate <i>Bacillus cereus</i> on potato

Luo, Ke,Kim, Seon Young,Wang, Jun,Oh, Deog-Hwan Elsevier 2016 FOOD SCIENCE AND TECHNOLOGY -ZURICH- Vol.73 No.-

<P><B>Abstract</B></P> <P>Slightly acid electrolyzed water (SAcEW) and ultrasound (US) treatment have emerged as an environmental-friendly antimicrobial agent. However, SAcEW treatment alone shows low antimicrobial efficiency. Therefore, the aim of this study was to develop a hurdle approach that combined SAcEW and US to improve the antimicrobial effect against <I>Bacillus cereus</I> as well as inhibition of the growth on potato. US treatment under different conditions of dip times, acoustic energy densities (AED) and temperatures were conducted to obtain the optimal condition. Our findings demonstrate that 3 min of US with 400 W/L of AED at 40 °C treatment (US + 40 °C) significantly (<I>p</I> ≤ 0.05) reduced <I>B. cereus</I> population by 2.3 ± 0.1 log CFU/g with minimal change in the color of potato. In addition, 3 min of SAcEW (pH, 5.3–5.5; ORP, 958–981 mV; ACC, 28–30 mg/L) simultaneous with US+40 °C treatment (SAcEW + US+40 °C) an approximately 3.0 log CFU/g reduction in <I>B. cereus</I>. Furthermore, SAcEW + US+40 °C treatment efficiently extended lag time of <I>B. cereus</I> by 0.2–10.5 hrs, reduced that of specific growth rate by 0.01–0.23 log CFU/h during storage at different temperatures from 5 to 35 °C. Therefore, this combined hurdle technology is capable of improving microbial safety of potato during storage and distribution.</P> <P><B>Highlights</B></P> <P> <UL> <LI> <I>Bacillus cereus</I> was detected in raw potato with approximately 3.0 log CFU/g. </LI> <LI> SAcEW combined with US treatment caused synergistic effect against <I>B. cereus.</I> </LI> <LI> Antimicrobial effect was enhanced by increasing acoustic energy density in ultrasound treatment. </LI> <LI> SAcEW + US+40 °C treatment not only extended the lag time but also reduced specific growth rate of <I>B. cereus.</I> </LI> </UL> </P>

Paper-Based Radial Chromatographic Immunoassay for the Detection of Pathogenic Bacteria in Milk

Luo, Ke,Ryu, Jian,Seol, In-Hye,Jeong, Ki-Baek,You, Sang-Mook,Kim, Young-Rok American Chemical Society 2019 ACS APPLIED MATERIALS & INTERFACES Vol.11 No.50

<P>Here, a paper-based radial flow chromatographic immunoassay (RFCI) employing gold nanoparticles (AuNPs) as chromatic agents was developed for the detection of <I>Escherichia coli</I> O157:H7 in whole milk. A 4-repeated gold-binding peptide-tagged (4GBP) streptococcal protein G (SPG) fusion protein was constructed as a bifunctional linker to immobilize antibodies on the surface of AuNPs with a well-oriented form based on the specific affinity of GBP and SPG to the gold and Fc portion of the antibody, respectively. 4GS@AuNPs prepared with the bifunctional linker protein exhibited excellent colloidal stability even at high salt concentrations of up to 500 mM, which is a critical requirement for its application to a broad range of biological and food samples. The enhanced colloidal stability and excellent binding capability of the immuno-4GS@AuNPs toward target bacteria lowered the detection limit of RFCI for target pathogenic bacteria in whole milk as low as 10<SUP>3</SUP> CFU/mL, which is by an order of magnitude lower than that of conventional immuno-AuNPs prepared with physical adsorption of antibodies. The RFCI pattern could also be converted into a grayscale value by simple image processing for quantitative determination of target pathogenic bacteria. This paper-based detection system would provide an effective means of monitoring the presence of food-borne pathogens in real food samples with naked eyes.</P> [FIG OMISSION]</BR>