Experimental Design, Equilibrium Modeling and Kinetic Studies on the Adsorption of Methylene Blue by Adsorbent: Activated Carbon from Durian Shell Waste

For the first time, activated carbon from a durian shell (ACDS) activated by H₂SO₄ was successfully synthesized in the present study. The fabricated ACDS has a porous surface with a specific surface area of 348.0017 m²·g^-1, average capillary volume of 0.153518 cm³·g^-1, the average pore diameter of 4.3800 nm; ash level of 55.63%; humidity of 4.74%; density of 0.83 g·cm^-3; an iodine index of 634 mg·g^-1; and an isoelectric point of 6.03. Several factors affecting Methylene Blue (MB) adsorption capacity of ACDS activated carbon was investigated by the static adsorption method, revealing that the adsorption equilibrium was achieved after 90 min. The best adsorbent pH for MB is 7 and the mass/volume ratio is equal to 2.5 g·L^-1. The MB adsorption process of ACDS activated carbon follows the Langmuir, Freundlich, Tempkin, and Elovich isotherm adsorption model, which has determined the maximum adsorption capacity for MB of ACDS as q_max = 57.47 mg·g^-1. The MB adsorption process of ACDS follows the of pseudo-second-order adsorption kinetic equation. The Weber and Morris Internal Diffusion Model, the Hameed and Daud External Diffusion Model of liquids have been studied to see if the surface phase plays any role in the adsorption process. The results of thermodynamic calculation of the adsorption process show that the adsorption process is dominated by chemical adsorption and endothermic. The obtained results provide an insight for potential applications of ACDS in the treatment of water contaminated by dyes.

Optimization of the Essential Oil Extraction Process from Dong Van Marjoram (E. winitiana var. dongvanensis Phuong.) by Using Microwave Assisted Hydrodistillation, and the Bioactivities of the Oil Against Some Cancer Cell Lines and Bacteria

This study reports on the optimization of a microwave-assisted distillation process to obtain Dong Van marjoram essential oil, and the determination of its composition, content of constituents, and cytotoxic and antimicrobial activities. Using the response surface method (RSM), the optimal essential oil distillation conditions were determined as material size 0.74 (cm), water to material ratio 4.14:1 (mL/g), microwave power 302.4 (W), and distillation time 2.1 hours. At optimal conditions, the mass of Dong Van marjoram essential oil obtained was 0.887 ± 0.007 g, corresponding to a content of 0.6% essential oil in the material. GC-MS and GC-FID methods showed that the main chemical constituents of Dong Van marjoram essential oils obtained were rosefuran epoxide (44.9%), caryophyllene (10.8%), germacrene D (2.6%), and α-humulene (1.3%). The essential oil exhibited moderate inhibition against both tested cancer cell lines, with IC50 values of 23.9 µg/mL (for PC3) and 56.2 µg/mL (for A549). However, the oil exhibited strong effectiveness against three bacterial strains, Escherichia coli, Bacillus subtilis, and Staphylococcus aureus, and a yeast strain, Saccharomyces cerevisiae, with minimal inhibitory concentration (MIC) values ranged from 50 to 100 µg/mL.

Lipid composition and molecular species of phospholipid in oyster Crassostrea lugubris (Sowerby, 1871) from Lang Co Beach, Hue Province, Vietnam

Oysters are widely distributed worldwide, but are mainly concentrated in tropics and subtropics. Total lipid (TL), fatty acid (FA) composition of TL and polar lipid (PoL) fractions, phospholipid (PL) class, and molecular species composition in soft tissues of Crassostrea lugubris were investigated for the first time from Vietnam. Phosphatidylglycolic acid (PGA) is the new phospholipid class first identified in marine species in general and Crassostrea lugubris in particular. Main eight classes of PL were determined in PoL fraction: diphosphatidylglycerol (DPG), phosphatidylethanolamine (PE), phosphatidylcholine (PC), phosphatidylinositol (PI), phosphatidylserine (PS), ceramide aminoethylphosphonate (CAEP), CAEP with hydroxylated FAs (CAEP-OH), and lysophosphatidylcholine. PE and PC accounted for approximately 63% of total known PL. Polyunsaturated FAs accounted for more than 30% of TL. Ninety molecular species of glycerophospholipids, including PGA, PE, PC, PS, PI, DPG, and PG, and sphingophosphonolipids (CAEP) were identified in PoL. Alkenyl-acyl forms of glycerophospholipids were predominated in the molecular species of PGA, PE, and PS. PGA 38:1 (p18:0/20:1), PE 40:6 (p18:0/22:6 and p18:1/22:5), PC 30:0 (14:0/16:0), PS 38:1 (p18:0/20:1), PI 40:5 (20:1/20:4), PG 32:0 (16:0/16:0), DPG 88:24 (22:6/22:6/22:6/22:6), and CAEP 34:2 (d18:2/16:0) were major molecular species.

Optimization of Murrayafoline A ethanol extraction process from the roots of Glycosmis stenocarpa, and evaluation of its Tumorigenesis inhibition activity on Hep-G2 cells

Glycosmis stenocarpa is a species of shrub found in the Northern provinces of Vietnam. Its roots contain different carbazolic derivatives, mainly Murrayafoline A (Mu-A), which exhibits valuable biological activities. In this study, we performed an extraction of Mu-A from the roots of G. stenocarpa and optimized this process using response surface methodology (RSM) according to a central composite design, with three independent parameters including extraction time (min), extraction temperature (°C), and solvent/material ratio (mL/g). Two dependent variables were the Mu-A content (mg/g raw materials) and extraction efficiency (%). The optimal conditions to extract Mu-A were found to be as follows: extraction temperature, 67°C; extraction time, 165 min; and solvent/material ratio, 5:1. Under these conditions, the Mu-A content and extraction efficiency were 38.94 ± 1.31 mg/g raw materials and 34.98 ± 1.18%, respectively. Mu-A exhibited antiproliferation and antitumor-promoting activity against the HepG-2 cell line. The present optimization work of Mu-A extraction from G. stenocarpa roots contributed to the attempt of designing a large-scale extraction process for the compound and further exploitation of its potential in vivo applications.

Rational design of magnetically separable core/shell Fe3O4/ZnO heterostructures for enhanced visible-light photodegradation performance

Magnetically separable core/shell Fe₃O₄/ZnO heteronanostructures (MSCSFZ) were synthesized by a facile approach, and their application for enhanced solar photodegradation of RhB was studied. The formation mechanism of MSCSFZ was proposed, in which Fe₃O₄ nanoparticles served as a template for supporting and anchoring the ZnO crystal layer as the shells. The morphology of MSCSFZ can be varied from spherical to rice seed-like structures, and the bandgap was able to be narrowed down to 2.78 eV by controlling the core–shell ratios. As a result, the MSCSFZ exhibited excellent visible-light photocatalytic activity for degradation of rhodamine B (RhB) in aqueous solution as compared to the controlled ZnO nanoparticles. Moreover, MSCSFZ could be easily detached from RhB solution and maintained its performance after 4 cycles of usage. This work provides new insights for the design of high-efficient core/shell recyclable photocatalysts with visible light photocatalytic performance.

Magnetically separable core/shell Fe₃O₄/ZnO heteronanostructures (MSCSFZ) were synthesized by a facile approach, and their application for enhanced solar photodegradation of RhB was studied.

Simultaneous removal efficiency of H2S and CO2 by high-gravity rotating packed bed: Experiments and simulation

This study explores the possibility of applying high-gravity rotating packed bed (HGRPB) in removing H2S and CO2 from biogas. Ca(OH)2 aqueous solution was used as the absorbent in this study. Different experimental conditions including solution pH, rotating speed (R S) of HGRPB, gas flow rate (Q G), and liquid flow rate (Q L) were investigated with respect to the removal efficiency (E) of H2S and CO2. The experimental and simulated results show that the optimal removal efficiency of H2S and CO2 using HGRPB achieved nearly the same as 99.38 and 99.56% for removal efficiency of H2S and 77.28 and 77.86% for removal efficiency of CO2, respectively. Such efficiencies corresponded with the following optimal conditions: a solution pH of 12.26, HGRPB reactor with the rotating speed of 1,200 rpm, the gas flow rate of 2.46 (L/min), and the liquid flow rate of 0.134 (L/min).

Isolation of Penicillium citrinum from Roots of Clerodendron cyrtophyllum and Application in Biosynthesis of Aglycone Isoflavones from Soybean Waste Fermentation

Soybeans offer an abundant source of isoflavones, which confer useful bioactivities when existing in aglycone forms. The conversion of isoflavones into aglycones via fermentation of soybean products is often realized by β-glucosidase, an enzyme produced by fungi. In this study, a filamentous fungus, Clerodendron cyrtophyllum, was isolated from root of Clerodendron cyrtophyllum Turcz, which was able to produce the highest activity of β-glucosidase up to 33.72 U/mL at 144 h during fermentation on Potato Dextrose Broth (PDB). The obtained fungus was grown on isoflavones-rich soybean extract to produce genistein and daidzein, achieving the conversion rate of 98.7%. Genistein and daidzein were isolated and purified by column chromatography using hexane/acetone (29:1/1:1), reaching purities of over 90% of total isoflavones, as identified and determined by TLC, LC-MS/MS, and ¹H and ¹³C NMR spectroscopy. These results imply that the isolated P. citrinum is a potential fungal strain for industrial-scale production of genistein and daidzein from isoflavones-containing soybean extracts. These products may serve as potential raw materials for manufacture of functional foods that are based on aglycones.

Fatty Acid, Lipid Classes and Phospholipid Molecular Species Composition of the Marine Clam Meretrix lyrata (Sowerby 1851) from Cua Lo Beach, Nghe An Province, Vietnam

This study aims to analyze compositions of fatty acids and phospholipid molecular species in the hard clams Meretrix lyrata (Sowerby, 1851) harvested from Cua Lo beach, Nghe An province, Viet Nam. Total lipid of hard clams Meretrix lyrata occupied 1.7 ± 0.2% of wet weight and contained six classes: hydrocarbon and wax (HW), triacylglycerol (TAG), free fatty acids (FFA), sterol (ST), polar lipid (PoL), and monoalkyl diacylglycerol (MADAG). Among the constituents, the proportion of PoL accounted was highest, at 45.7%. In contrast, the figures for MADAG were lowest, at 1.3%. Twenty-six fatty acids were identified with the ratios of USAFA/SAFA was 2. The percentage of n-3 PUFA (ω-3) and n-6 PUFA (ω-6) was high, occupying 38.4% of total FA. Among PUFAs, arachidonic acid (AA, 20:4n-6), eicosapentaenoic acid (EPA, 20:5n-3), docosapentaenoic acid (DPA, 22:5n-3), and docosahexaenoic acid (DHA, 22:6n-3) accounted for 3.8%, 7.8%, 2.2% and 12.0% of total lipid of the clam respectively. Phospholipid molecular species were identified in polar lipids of the clams consisting six types: phosphatidylethalnolamine (PE, with 28 molecular species), phosphatidylcholine (PC, with 26 molecular species), phosphatidylserine (PS, with 18 molecular species), phosphatidylinositol (PI, with 10 molecular species), phosphatidylglycerol (PG, with only one molecular species), and ceramide aminoethylphosphonate (CAEP, with 15 molecular species). This is the first time that the molecular species of sphingophospholipid were determined, in Meretrix lyrata in particular, and for clams in general. Phospholipid formula species of PE and PS were revealed to comprise two kinds: Alkenyl acyl glycerophosphoethanolamine and Alkenyl acyl glycerophosphoserine occupy 80.3% and 81.0% of total PE and PS species, respectively. In contrast, the percentage of diacyl glycero phosphatidylcholine was twice as high as that of PakCho in total PC, at 69.3, in comparison with 30.7%. In addition, phospholipid formula species of PI and PG comprised only diacyl glycoro phospholipids. PE 36:1 (p18:0/18:1), PC 38:6 (16:0/22:6), PS 38:1 (p18:0/20:1), PI 40:5 (20:1/20:4), PG 32:0 (16:0/16:0) and CAEP 34:2 (16:2/d18:0) were the major molecular species.

Treatment of uncomplicated falciparum malaria in southern Vietnam: can chloroquine or sulfadoxine-pyrimethamine be reintroduced in combination with artesunate?

The effectiveness of chloroquine or sulfadoxine-pyrimethamine administered with artesunate for treating uncomplicated falciparum malaria was assessed in 2 Vietnamese provinces where the sensitivity of parasites in vitro to conventional therapies had increased with the removal of drug pressure. In the province of Dac Lac, where potential malaria exposure begins at birth, 57 subjects (mean age, 9.6 years) were randomized to receive artesunate-chloroquine (group 1) or artesunate-sulfadoxine-pyrimethamine (group 2). In the province of Binh Phuoc, 66 nonimmune workers and their relatives (mean age, 24.2 years) were similarly randomized. By day 28 of follow-up, >96% of Dac Lac patients and <52% of Binh Phuoc patients in group 1 and group 2 had an in vivo response that demonstrated sensitivity to therapy. PCR-confirmed cure rates paralleled in vivo results among patients in Binh Phuoc, but PCR results identified 9 (15.7%) of the Dac Lac patients as having experienced asymptomatic, submicroscopic recrudescences. In Dac Lac, pfcrt K76T was near fixation, but infection with parasites with this mutation predicted recrudescence among group 1 patients in Binh Phuoc. Common pfdhfr mutations did not predict outcome in group 2. The successful reintroduction of conventional therapies in combination with artesunate depends on epidemiological and/or parasitological factors.

Determination of arsenic in urine by atomic absorption spectrophotometry for biological monitoring of occupational exposure to arsenic

An atomic absorption spectrophotometric (AAS) method was successfully applied to analysis of urine for arsenic (As) as a measure of biological monitoring of occupational exposure to As in Vietnam. The application of the method to urine samples from 75 non-exposed control urbanites (after 2-day abstinence from sea foods) gave a reference level of 62.4 +/- 11.6 microg/l (as mean +/- S.D.), from which the upper limit of the normal value (74 microg/l as mean +/- 1 S.D.) and the acceptable limit (100 microg/l as mean +/- 3S.D.) were deduced. Further application to urine samples from 147 workers occupationally exposed to As in Bacthai Non-ferrous Metallurgic Corporation showed significantly elevated levels of As in urine, with mean +/- S.D. of 78.5 +/- 20.2 microg/l. Improvement of working conditions to reduce As exposure resulted in substantial reduction in the ratio of those with urinary As at the level in excess of the acceptable limit. The practical importance of total arsenic determination in urine after 2-day sea food abstinence is discussed in connection with current conditions in analytical laboratories in Vietnam.

Measurement of Young's modulus in the in vivo human vocal folds

Currently, surgeons have no objective means to evaluate and optimize results of phonosurgery intraoperatively. Instead, they usually judge the vocal folds subjectively by visual inspection or by listening to the voice. This paper describes a new device that measures Young's (elastic) modulus values for the human vocal fold intraoperatively. Physiologically, the modulus of the vocal fold may be important in determining the nature of vocal fold vibration in normal and pathologic states. This study also reports the effect of recurrent laryngeal nerve stimulation on Young's modulus of the human vocal folds, measured by means of transcutaneous nerve stimulation techniques. Young's modulus increased with increases in current stimulation to the recurrent laryngeal nerve. Ultimately, Young's modulus values may assist surgeons in optimizing the results of various phonosurgeries.