Enzymatic Synthesis of Pure Maltohexaose from α-Cyclodextrin

Phu Cuong Nguyen,Ji-Yun Kwak,Min-Jee Yoo,Jong-Tae Park,Kwan-Hwa Park 한국당과학회 2016 한국당과학회 학술대회 Vol.2016 No.01

Maltohexaose (G6) is a maltodextrin consisted of six-glucose in α-1,6-glycosidic linkages and essential research tool in food, cosmetic and pharmaceutical. In previous study, we have proven that the possibility of large-scale continuous production of pure maltodextrins from cyclodextrins (CDs) using Pyrococcus furiosus thermostable amylase with immobilization in a packed-bed reactor (PBR). In this study, we used this PBR for G6 production from α-CD. After enzyme reaction, 1-decanol was added to G6 mixture as precipitating agent with a 1:1 ratio of 1-decanol to α-CD. In which, the unreacted α-CD was precipitated, then it was separated by centrifugation. Finally, the G6-product was obtained in homogeneous form and high-purity (95 %). Through this study, we successfully demonstrated the enzymatic synthesis method to produce pure G6 from α-CD.

Synthesis of Maltoheptaose Fatty Ester by Yeast Lipase and Their Emulsion Functions

Phu Cuong Nguyen,Thi My Tuyen Nguyen,Chang-KyuLee,Il-NamOh,Min-Jee Yoo,Kyu-BeenPark,Jae-HanKim,Hyun-JooAn,Jong-TaePark 한국당과학회 2018 한국당과학회 학술대회 Vol.2018 No.07

Enzymatic syntheses of sugar fatty acid (FA) esters are important because of their wide range of applications in the food, cosmetic, and pharmaceutical industries. These molecules are commonly synthesized from F As and mono-, or di-saccharides by chemical or enzymatic esterification. Previously, sugar esters were produced using oligosaccharide, and interfacial tension values and inhibitory effects towards tumor cell lines were improved when higher DP saccharides were used. In this study, the direct esterification of maltoheptaose (G7) with vanous length of F As was investigated by the catalytic action of Candida antartica lipase B. Among the F As palmitic acid (PA) was the best substrate for the G7 ester formation. Optimal reaction conditions including solvent composition and molar ratio of G 7: P A were established for the G7-PA. The conversion yield and sugar ester structure were analyzed using various instrumental analyses. The results showed that G7-PA monoester was successfully synthesized with a molar ratio of I :20 (G7: PA) in I 0% DMSO of t-butanol at 60°C, and the conversion yield was over than 21%. The position of ester bond formation was identified that PA was attached to C-6 of the reducing end glucosyl moiety. The melting temperature of G7- PA monoester was reached at 56 °C, lower than that of pure G7 and PA. In addition, the G7- p A esters and commercial sucrose esters were compared as emulsifiers. Both type of sugar esters prevented coalescence during 7 days and showed good emulsifying properties in 0/W emulsions since the droplets diameter did not have significant change during the storage.

Enzymatic synthesis and characterization of maltoheptaose-based sugar esters

Nguyen, Phu Cuong,Nguyen, My Tuyen Thi,Lee, Chang-Kyu,Oh, Il-Nam,Kim, Jae-Han,Hong, Soon-Taek,Park, Jong-Tae Applied Science Publishers 2019 Carbohydrate Polymers Vol.218 No.-

<P> In this study, maltoheptaose (G7)-based sugar esters were synthesized from maltoheptaose and fatty acids (C10-C16) using a commercial lipase. With the exception of dimethyl sulfoxide (DMSO; 76.4%, w/v), G7 showed only limited solubility in organic solvents. Among the fatty acids, palmitic acid (PA) was the best substrate for G7-based ester formation. G7-PA ester was successfully synthesized as the monoester structure exclusively in 10% DMSO of t-butanol with a 22% conversion yield. NMR and enzymatic analyses of the purified monoester product revealed that the ester bond in the G7 was located at C-6 of the glucose at the reducing end. The G7-PA monoester showed the melting temperature at 56.3℃ that was 6.5℃ lower than that of the free PA and exhibited a different endothermic pattern from the free G7. The G7-PA monoester exhibited excellent emulsifier potential with more even droplet size distribution compared with the commercial sucrose esters for an oil-in-water emulsion system. </P>

Enzymatic synthesis of pure maltodextrins and their novel derivatives

Phu Cuong Nguyen,My Tuyen Thi Nguyen,Chang-Kyu Lee,Wang-Hee Lee,Il-Nam Oh,Jae-Han Kim,Soon-Taek Hong,Jong-Tae Park 한국당과학회 2022 한국당과학회 학술대회 Vol.2022 No.07

Maltodextrin in specific length is of great interest because of its wide industrial applications. Previously, we have proven that Pyrococcus furiosus thermostable amylase (PFTA) produces high purity maltoheptaose (G7) from β-cyclodextrin (CD) at early reaction time. However, the production of pure G7 is a cost and time-consuming process. Therefore, this work has designed an optimal continuous process for pure G7 production from β-CD using PFTA with immobilization in a packed-bed reactor (PBR). The optimal conditions determined using the response surface method for the maximized G7-purity of 96.3% were predicted at 4.7 ml/min of flow rate, 1.1% substrate, and 48.7 °C. As a result, the immobilized PFTA in PBR retained 85% of the initial activity after six cycles of 24 h intervals, and the product purity was unchanged. Also, maltohexaose (G6) and maltooctaose (G8) at high purity (92-97%) were produced by continuously supplying CDs to the PFTA-PBR under the same optimized condition of G7. In addition, a new method based on preparative reversed-phase liquid chromatography was developed to purify maltodextrins in specific lengths (DP 3-26) with high purity from the reaction mixture of G6-G8 substrates with Thermotoga maritima maltosyltransferase. On the other hand, novel G7-based sugar esters were also synthesized and investigated for emulsifying properties. As a result, G7-fatty acids (C10–C16) esters were produced with a high conversion yield (90-95%) under the optimal conditions (10% of DMSO, 0.2 of G7/ fatty acids molar ratio, 33.5 U of immobilized Candida antarctica lipase B) for 24 h of incubation at 60 °C. Notable, G7-palmitate (PA) exhibited emulsifying properties better than commercial sucrose-PA ester, especially in acidic conditions. It is feasible that the number of the hydroxyl groups and the size of G7 moiety provide that distinctive property of G7-PA. Therefore, applications of G7-PA in foods, cosmetics, and drug delivery under extreme pH conditions are promising.

Advanced analysis for planar steel frames with semi-rigid connections using plastic-zone methodAdvanced analysis for planar steel frames with semi-rigid connections using plastic-zone method

Phu-Cuong Nguyen,김승억 국제구조공학회 2016 Steel and Composite Structures, An International J Vol.21 No.5

This paper presents a displacement-based finite element procedure for second-order distributed plasticity analysis of planar steel frames with semi-rigid beam-to-column connections under static loadings. A partially strain-hardening elastic-plastic beam-column element, which directly takes into account geometric nonlinearity, gradual yielding of material, and flexibility of semi-rigid connections, is proposed. The second-order effects and distributed plasticity are considered by dividing the member into several sub-elements and meshing the cross-section into several fibers. A new nonlinear solution procedure based on the combination of the Newton-Raphson equilibrium iterative algorithm and the constant work method for adjusting the incremental load factor is proposed for solving nonlinear equilibrium equations. The nonlinear inelastic behavior predicted by the proposed program compares well with previous studies. Coupling effects of three primary sources of nonlinearity, geometric imperfections, and residual stress are investigated and discussed in this paper.

A new improved fiber plastic hinge method accounting for lateral-torsional buckling of 3D steel frames

Nguyen, Phu-Cuong,Kim, Seung-Eock Elsevier 2018 Thin-Walled Structures Vol.127 No.-

<P><B>Abstract</B></P> <P>This paper presents a new advanced analysis method, specifically a new improved fiber plastic hinge method, for analyzing the nonlinear inelastic behavior of 3D steel frames accounting for lateral-torsional buckling. The second-order effects are considered by the use of the geometric stiffness matrix and stability functions obtained from the exact solution of beam-columns under axial force and bending moments at two ends. The spread of plasticity along the member length due to both residual stresses and the impact of axial force is considered by utilizing the Column Research Council (CRC) tangent modulus concept, while the gradual yielding due to flexure is represented by two fiber plastic hinges at the ends of the element. The lateral-torsional buckling stiffness matrix is established by the virtual work principle using the updated Lagrangian formulation. The generalized displacement control method is applied to solve the nonlinear equilibrium equations in an incremental-iterative scheme. The nonlinear load-displacement behavior and ultimate load results compare well with those of previous studies. It is concluded that accurately using only one element per member likely predicts the second-order inelastic behavior of 3D steel frames including the effect of lateral-torsional buckling.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A new improved fiber plastic hinge method for analyzing steel frames is presented. </LI> <LI> Stability functions are employed to predict second-order effects accurately, save computational time. </LI> <LI> The effect of lateral-torsional buckling is considered by a simple way. </LI> <LI> The proposed program can be developed for daily engineering design. </LI> </UL> </P>

Risk Factors Affecting Equipment Management in Construction Firms

Cuong Phu PHAM,Phong Thanh NGUYEN,Phuong Thanh PHAN,Quyen Le Hoang Thuy To NGUYEN,Loan Phuc LE,My Tien Ha DUONG 한국유통과학회 2020 The Journal of Asian Finance, Economics and Busine Vol.7 No.11

Mechanization and automation constitute an essential stage in the production and operation of any company, as one of the determinants of increase in labor productivity and decrease in product price, while significantly contributing to shortening of the lead time. Businesses are, therefore, able to quickly put projects into operation, improving economic efficiency, quality, and aesthetics, which speeds up the national economic growth. For the construction industry to be the most effective, modern construction equipment is a necessity. It is one of the five main resources of a construction project. Thus, effective construction equipment management contributes to the success of a project and benefits the relevant construction companies economically. This paper presents the critical risk factors affecting equipment management and proposes suitable solutions. The questionnaire-based survey with experienced experts in the construction sector on the management of the likelihood and consequence of risk factors revealed thirty-two risks for equipment management in construction companies. These factors fell into six groups: (i) site organization-related risks; (ii) management-related risks; (iii) owner-related risks; (iv) supplier-related risks; (v) legal risks, and (vi) site condition-related and external risks. The results showed that management-related factors contributed to the most significant risks and problems for equipment management in construction companies.

Magnetic adsorption - forward osmosis membrane hybrid system for rich arsenic wastewater treatment

Anh Nguyen(NGUYEN DUC ANH),Cuong Le(Phu Cuong Le),Am Jang(장암) 대한환경공학회 2022 대한환경공학회 학술발표논문집 Vol.2022 No.11

Copper Tolerance of Novel Rhodotorula sp. Yeast Isolated from Gold Mining Ore in Gia Lai, Vietnam

Kim Cuc Thi Nguyen,Phuc Hung Truong,Cuong Tu Ho,Cong Tuan Le,Khoa Dang Tran,Tien Long Nguyen,Manh Tuan Nguyen,Phu Van Nguyen 한국균학회 2023 Mycobiology Vol.51 No.6

In this study, twenty-five yeast strains were isolated from soil samples collected in the goldmining ore in Gia Lai, Vietnam. Among them, one isolate named GL1T could highly tolerateCu2þ up to 10 mM, and the isolates could also grow in a wide range of pH (3–7), and temperature(10–40 �C). Dried biomass of GL1 was able to remove Cu2þ effectively up to 90.49%with a maximal biosorption capacity of 18.1 mg/g at pH 6, temperature 30 �C, and incubationtime 60 min. Sequence analysis of rDNA indicated this strain was closely related toRhodotorula mucilaginosa but with 1.53 and 3.46% nucleotide differences in the D1/D2domain of the 28S rRNA gene and the ITS1-5.8S rRNA gene-ITS2 region sequence, respectively. Based on phylogenetic tree analysis and the biochemical characteristics, the strainappears to be a novel Rhodotorula species, and the name Rhodotorula aurum sp. nov. is proposed. This study provides us with more information about heavy metal-tolerant yeasts andit may produce a new tool for environmental control and metal recovery operations.

Exploring Critical Risk Factors of Office Building Projects

NGUYEN, Phong Thanh,PHAM, Cuong Phu,PHAN, Phuong Thanh,VU, Ngoc Bich,DUONG, My Tien Ha,NGUYEN, Quyen Le Hoang Thuy To Korea Distribution Science Association 2021 The Journal of Asian Finance, Economics and Busine Vol.8 No.2

Risks and uncertainty are unavoidable problems in management of projects. Therefore, project managers should not only prevent risks, but also have to respond and manage them. Risk management has become a critical interest subject in the construction industry for both practitioners and researchers. This paper presents critical risk factors of office building projects in the construction phase in Ho Chi Minh City, Vietnam. Data was collected through a questionnaire survey based on the likelihood and consequence level of risk factors. These factors fell into five groups: (i) financial risk factors; (ii) management risk factors; (iii) schedule risk factors; (iv) construction risk factors; and (v) environment risk factors. The research results showed that critical factors affecting office building projects are natural (i.e., prolonged rain, storms, climate effects) and human-made issues (i.e., soil instability, safety behaviors, owner's design change) and the schedule-related risk factors contributed to the most significant risks for office buildings projects in the construction phase in Ho Chi Minh City. They give construction management and project management practitioners a new perspective on risks and risk management of office buildings projects in Ho Chi Minh City and are proactive in the awareness, response, and management of risk factors comprehensively.