Jurnal Kimia Valensi
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Phenol Biosensor Development Using Bacillus megaterium And Pseudomonas fluorescens Microbes Consortium
Full text linkPhenol is a toxic industrial pollutant that must be monitored at a low cost and in real-time. Conventional amperometric biosensors based on a single enzyme or a single microorganism often suffer from limited sensitivity and operational drift. Here, we report a microbial consortium biosensor that couples Bacillus megaterium, which supplies phenol-degrading enzymes and structural stability, with Pseudomonas fluorescens, whose electroactive biofilm enhances electron transfer to a screen-printed carbon electrode (SPCE). The electrode potential was swept at 100 mV s⁻¹ between –1 V and +1 V (i.e., a 2 V window traversed in 20 s) to capture the full redox range of phenol by Cyclic Voltammetry (CV). The oxidation peak current grew linearly with phenol concentration from 27 to 137 mg/L (R² = 0.98), giving a sensitivity of 1.30 µA mg/L and a limit of detection of 13.6 mg/L. Compared with our previously tested single-microbe sensors, the consortium lowered the LOD threefold while maintaining long-term signal stability (>30 days). These results demonstrate that complementary metabolic pathways and the conductive biofilm of P. fluorescens synergistically enhance the electrochemical response provided by B. megaterium. The consortium-based SPCE platform, therefore, offers a robust, inexpensive tool for on-site phenol monitoring in environmental and industrial settings
Preparation of Pectin Membranes with Polyvinyl Alcohol (PVA) Blended Method as Dialysis Membrane for Urea Transport
Full text linkPectin has shown the potential to act as membranes in a variety of applications, such as in biomedical applications such as that carried out in this study. This study aims to modify pectin with polyvinyl alcohol (PVA) for hemodialysis membrane applications. Pectin-PVA membranes were made by immersing the membrane with 4% PVA and tested for the membrane\u27s filtration capacity for transport. Pectin-PVA membranes were tested using Tensile Test, Fourier Transform Infrared (FTIR), X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), and Thermal Test. The results showed that the pectin blended polyvinyl alcohol (PVA) membrane was successfully synthesized, confirmed by the spectra on FTIR there were OH vibrations, –CH2, –CH, -CO (ester) and CO (ether) bonds, PVA will increase the stress and strain value, XRD data shows that the membrane has a crystalline structure, SEM data shows that the membrane including in the microspheres, and the membrane undergoes carbonization at a temperature of around 400 °C there is an increase in the absorbance value, and the urea transport process increases the absorption of urea every hour.
Assessment of Macronutrient Dynamics in a Tropical Watershed: A Study from Bengkulu River and Estuary Indonesia
Full text linkThis study assesses the sources, transport, and distribution of macronutrients, including nitrate, nitrite, silicate, and phosphate, starting from the upper stream of the Bengkulu River, which is the biggest river in Bengkulu Province, to the coastal seawater of the eastern tropical Indian Ocean. The sampling was conducted using an acid-washed polypropylene beaker and placed in acid-cleaned 5 L polyethylene containers during the dry season in July 2024. The water samples were collected from the surface waters of 15 stations. The macronutrients in the water samples were determined using a spectrophotometer UV-Vis following the Strickland and Parsons method. Macronutrient analysis was conducted in LATERIO BRIN, Jakarta, Indonesia. The concentration of analysed macronutrients ranged from 0.005 - 0.058 mgN-NO3/L for nitrate, <0.001 - 0.014 mgN-NO2/L for nitrite, 0.163 - 9.314 mgSi-Si(OH)4/L for silicate, and 0.01 - 0.085 mgP-PO4-/L for phosphate. Several stations, including Stations 6, 10, and 14, exhibited relatively elevated nitrate concentrations, which were further supported by similarly high phosphate levels. Stations 6, 10, and 14, situated near areas of intense anthropogenic activity in Bengkulu City, suggest that human-induced inputs have enriched the water environment with macronutrients. The highest silicate concentration was observed at Station 1, located upstream in the Bengkulu River. This aligns with previous findings and underscores the role of weathering processes in controlling silicate distribution. Compared to the macronutrient concentration guidelines for river water set by Indonesian Government Regulation 2021 No. 22, the nitrite concentrations at certain river stations exceeded the safety threshold for aquatic biota. In contrast, nitrate and phosphate levels remained within the safe range
Natural Zeolite as Mo and MoP Catalysts Support for Catalytic Deoxygenation of Jatropha Oil
Full text linkNon-edible oil, such as Jatropha oil, is an interesting feedstock for the development of renewable diesel (green diesel). Catalytic deoxygenation using natural zeolite-supported Mo-based catalysts is a promising process for the conversion of Jatropha oil to green diesel. Mo and MoP catalysts supported on natural zeolite were synthesized by wet impregnation at a concentration of 5% (w/w). The catalysts were characterized by XRD, XRF, SAA and NH3-TPD. The catalysts were successfully synthesized with the appearance of Mo and MoP peaks on the catalyst diffractogram. XRF results also showed that Mo and P were present in the catalyst. Metal impregnation decreased the surface area and pore volume of the catalyst, but increased the average pore diameter. The NH3-TPD profile of the catalyst showed that the weak acid sites of both catalysts were larger than the strong acid sites. Based on the activity test of catalytic deoxygenation of Jatropha oil, the MoP/HZ catalyst produced a higher conversion (67%) and liquid product yield (79%) than Mo/HZ. This is associated with a larger pore diameter, so that the distribution of reactants on the catalyst surface is more optimal. However, the highest green diesel selectivity of 82% is produced by the Mo/HZ catalyst. The Mo/HZ catalyst is more oriented towards the HDO reaction, whereas the MoP/HZ catalyst is more oriented towards the DCO/DCO2 reaction
Hydrothermal Growth of Titanium Dioxide Thin Films on Conductive Substrates: Insights into Optical Properties
Full text linkTitanium dioxide (TiO2) thin films were deposited on fluorine-doped tin oxide (F:SnO2/FTO) conducting glass using the hydrothermal method. The X-ray diffraction (XRD) patterns confirmed that the TiO2 thin films crystallize in the rutile phase, exhibiting high crystallinity. The Fourier Transform Infrared (FTIR) spectrum confirmed the interaction between the FTO substrate and the TiO2 layer, indicated by an absorption peak in the range of 400 cm-1 to 900 cm-1. These peaks correspond to Ti–O–Ti and Ti–O vibrations within the octahedral structure of TiO₆ and Sn–O–Ti vibrations, indicating the bonding between the FTO substrate and the TiO₂ surface. Scanning Electron Microscopy (SEM) images provide detailed visualization of the morphological features of the TiO₂ thin films deposited on FTO glass, as evidenced by the prolonged hydrothermal processing resulting in the formation of thicker films. In addition, the interface between the TiO₂ layer and the FTO substrate is well-defined and continuous. UV-Visible Diffuse Reflectance Spectroscopy (UV-Vis DRS) analysis showed enhanced light absorption with increasing film thickness, which was also visually noticeable. As a result, the band gap energy decreases with increasing thickness, indicating that less energy is required to excite electrons from the valence band to the conduction band
TLC Fingerprint Analysis and Evaluation of α-Glucosidase Inhibitory and Free Radical Scavenging Activity of Justicia gendarussa from Different Growth Locations
Full text linkJusticia gendarussa is known to have antioxidant and antidiabetic properties, which are related to the composition and concentration of its metabolites and influenced by differences in growth location. This study aims to evaluate changes in metabolite profiles and biological activities, such as the inhibition of α-glucosidase and free radical scavenging in J. gendarussa genotypes from Bogor, Cianjur, and Sukabumi. Changes in metabolite profiles were assessed using thin-layer chromatography (TLC) fingerprint analysis combined with principal component analysis (PCA). Bioautography TLC using DPPH was performed to confirm the presence of antioxidant compounds. In the TLC fingerprint analysis of J. gendarussa, we obtained 14 bands with good resolution. PCA successfully grouped J. gendarussa extracts based on growth location. The percentage of α-glucosidase inhibitory and free radical scavenging activity was significantly different, with the highest percentage of inhibition of α-glucosidase shown by the IIIS genotype (99.23%) and the highest free radical scavenging (91.35%) demonstrated by the IIB genotype. The results of TLC bioautography confirmed the presence of antioxidant compounds in J. gendarussa represented by bands with Rf 0.04, 0.32, and 0.80. This study concludes that growth location differences influence the variations in metabolite profiles, α-glucosidase inhibitory activity, and free radical scavenging activity of J. gendarussa genotypes
Unraveling the Influence of Type and Position Heteroatoms (N, O, S) on Asphaltene Aggregation Patterns
Full text linkAsphaltenes, the heaviest fraction in petroleum and coal, are composed of polycyclic aromatic hydrocarbons (PAHs) with aliphatic side chains and heteroatoms (N, O, S). Previous studies have shown that these heteroatoms have a significant influence asphaltene aggregation. This study investigates the impact of heteroatom position and type, as well as solvent, on asphaltene aggregation behavior by employing molecular dynamics simulations of modified CA21 asphaltene. Simulations were conducted using GROMACS 2024.3. Analysis of simulation trajectories revealed that in water, all asphaltene models exhibited asphaltene-asphaltene radial distribution functions (RDFs) below 1 nm, indicating predominantly parallel or parallel-offset π-π interactions. In contrast, asphaltenes with an oxygen heteroatom at the end of the aliphatic chain when dissolved in hexane and toluene solvents, displayed unique shape aggregation, attributed to hydrogen bonding between the terminal oxygen atoms. The presence of heteroatoms within the aliphatic chain generally slowed aggregation, with the observed order of aggregation rates being S > N > O
TiO2/Zeolite Coal Fly Ash Nanocomposite for Photodegradation of Naphthol Blue Black Dye: Optimization and Mechanism under Visible Light
Full text linkNaphthol Blue Black (NBB) is a water-insoluble synthetic azo dye with a molecular weight of 616.49 g/mol that requires alkaline treatment for solubility and poses environmental risks by reducing water quality, increasing BOD and COD, and disrupting aquatic ecosystems. The TiO₂/Zeolite Fly Ash nanocomposite represents a promising material for the photocatalytic degradation of NBB. Analysis of the TiO2/zeolite fly ash nanocomposites revealed the presence of Ti-O-Si and Ti-O-Al functional groups, along with a suitable band gap energy value of 2.85 eV for visible light consumption. The average particle size is 62-75 nm, with a relatively high crystallinity of 95.64%. The insertion of TiO2 into the surface of the zeolite changes the size of the catalyst from 62-75 nm to 10 nm and 98.2% crystallinity. An emphasis was placed on the key parameters governing the degradation process. The test results showed that the degree of degradation increases at lower pH, while changes in catalyst dosage and initial dye concentrations do not significantly affect the degradation of NBB. The addition of H2O2 demonstrates the increasing degradation efficiency. The optimum operating process was carried out by adding 1.2 % (v/v) of H2O2, the pH 2, 0.1% (w/v) of catalyst, an initial concentration NBB of 12 mg/l, and irradiating under visible light for 75 minutes. It was a short period to produce the best conditions for degrading 12 mg/l naphthol blue-black, with a degradation efficiency of 99.68%. The rate of photodegradation kinetics had a reaction rate constant of 0.0312 min-1 and was followed a pseudo-first-order Langmuir-Hinshelwood. From the results, it was found that adsorption is an essential factor in the photodegradability of the dye. The linear transform of the Langmuir isotherm curve was further used to determine the characteristic parameters, which included the maximum absorbable dye quantity Qmax=11,8217 mgg-1. LC-MS/MS analysis identified the compounds formed through the photocatalytic degradation of naphthol blue-black dye into lower-molecular-weight molecules, such as benzoic acid, maleic acid, and phenol, which can gradually break down naturally into carbon dioxide and water
Isolation and Structural Characterization of Biflavonoids from Araucaria hunsteinii and Araucaria columnaris: Chemotaxonomic and Pharmacological Perspectives
Full text linkBiflavonoids are a distinctive class of dimeric flavonoids known for their diverse biological activities and chemotaxonomic significance. In this study, two biflavonoids were isolated from the acetone extracts of Araucaria hunsteinii twigs and Araucaria columnaris leaves collected from Bogor Botanical Garden, Indonesia. Chromatographic techniques, including Sephadex LH-20 column chromatography and preparative thin-layer chromatography, were employed for purification, followed by structural elucidation using LC-MS/MS and 1D/2D NMR spectroscopy. The compounds were identified as 4\u27,4\u27\u27\u27,7,7\u27\u27-tetra-O-methylcupressuflavone (1) and 7-O-methylcupressuflavone (2). Notably, this is the first report of 7-O-methylcupressuflavone isolated from A. columnaris leaves, providing new chemotaxonomic insights into the genus Araucaria. A literature-based pharmacological analysis revealed promising cytotoxic and α-glucosidase-inhibitory activities of the isolated compounds. These findings contribute to the phytochemical profiling and highlight the pharmaceutical potential of Araucaria-derived biflavonoids
In Silico Analysis of Tea Leaf Compounds Targeting Inflammatory Pathways and Acne-Related Genes
Full text linkAcne (Acne vulgaris) is a chronic skin disease affected by Cutibacterium acnes infection and inflammatory pathways that trigger innate immune responses, such as inflammasome activation. The expression of inflammation-related genes plays a critical role in acne pathogenesis and immune modulation. This study aims to identify compounds from tea leaves (Camellia sinensis var. assamica) that can treat acne by influencing the expression of inflammatory-related genes through in silico analysis. The GSE6475 dataset was utilized to identify differentially expressed genes (DEGs) between acne-affected and normal skin samples (each group n=6). A total of 573 DEGs were identified and mapped to the KEGG inflammatory pathway. The hub gene analysis results showed six genes, including CXCL1, STAT1, and PIK3 (adj. P-value < 0.05). These key genes were then used to cross-validate skin grouping with acne lesions and normal skin. The structure of compounds (natural products) in tea leaves (C. sinensis var. assamica) was obtained from the PubChem database, and their activity against target proteins associated with the identified key genes was predicted using the SkelSpheres descriptor and Support Vector Regression method. This quantitative structure–activity relationship (QSAR)-based machine learning approach was selected because it enables high-throughput prediction of inhibitory potential using chemical descriptors and experimentally derived bioactivity data, providing broader predictive power than conventional molecular docking or molecular dynamics, which rely mainly on structural and energetic estimations. The in-silico prediction results showed that compounds such as theobromine, assamsaponin, procyanidin, and caffeine have exhibited good predicted activity (IC₅₀ ranging from 1.125 to 1.320 μM) as potential inhibitors of the PI3K/Akt pathway, which is known to play a role in the pathogenesis of acne.