Face-centered Central Composite Design Research Articles

Hydrothermal Co-Liquefaction of Food and Plastic Waste for Biocrude Production

In this study, hydrothermal co-liquefaction of restaurant waste for biocrude production was conducted. The feedstock was resembled using the organic fraction of restaurant waste and low-density polyethylene, polypropylene, polystyrene, and polyethylene terephthalate, four plastic types commonly present in municipal solid waste. Using design of experiment and a face-centered central composite design, three factors (feedstock plastic fraction, temperature, time) were varied at three levels each: feedstock plastic fraction (0, 0.25, 0.5), temperature (290 °C, 330 °C, 370 °C), and reaction time (0 min, 30 min, 60 min). The literature reports positive synergistic interactions in hydrothermal co-liquefaction of biomass and plastics; however, in this work, only negative synergistic interactions could be observed. A reason could be the high thermal stability of produced fatty acids that give little room for interactions with plastics. At the same time, mass might transfer to other product phases.

Statistical optimization for greener synthesis of multi-efficient silver nanoparticles from the Hypocrea lixii GGRK4 culture filtrate and their ecofriendly applications

The culture filtrate of Hypocrea lixii GGRK4 played a vital role as a reducing and stabilizing agent in the mycosynthesis of silver nanoparticles (AgNPs) using silver nitrate (AgNO3). The extracellular extract derived from fungi emerged as a noteworthy option for synthesizing AgNPs due to its potential composition of metabolites, including enzymes and other bioactive substances. Hence, the presence of a dark brown color serves as a key indicator for the biosynthesis of AgNPs through the reduction of Ag (I) ions to Ag by the fungal culture filtrate. To facilitate the synthesis of AgNPs, a combination of hybrid technologies, specifically the “one factor at a time” approach and statistical tools such as response surface methodology, was used using a face-centered central composite design (FCCCD). Utilizing a modified CX medium with pH of 5.02 supported the fungi synthesizing AgNPs at a temperature of 30°C. The multi-efficient AgNPs were characterized through various techniques, including UV–visible spectrophotometry, zeta size and potential analysis using a zeta size analyzer, transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and fluorescence spectroscopy. The biosynthesized AgNPs have significant associated functional groups, revealed by FTIR analysis. TEM histogram analysis showed that these multi-efficient AgNPs have a size of 17.34 nm. Similarly, they have emission and excitation spectra of 450 nm and 390 nm, respectively, revealed by fluorescence spectrum analysis. Compared to the standard, the biosynthesized AgNPs have significant antibacterial and free radical scavenging properties and dye degradation capability. Additionally, the half-maximal inhibitory concentration (IC50) value was found statistically significant based on t-test analysis. Finally, the biosynthesized AgNPs could be used in potential applications encompassing ecofriendly degradation, antimicrobial activity, and therapeutic applications, such as free radical scavenging properties.

Optimization of barrel temperature and feed moisture content for better physicochemical and sensory properties of extruded snacks from blends of finger millet, sweet potato, and soybean composite flour using response surface methodology

Extruded snacks are commonly made with cereals with good expansion properties but low in essential nutrients such as protein and vitamins. The incorporation of legume and vegetable crops into cereal improves the nutritional value of cereal-based extruded snacks. This study aimed to develop a nutrient-rich optimized extruded snack by incorporating orange-fleshed sweet potato, finger millet, and soybean flour. The extrusion processing conditions were barrel temperature (90–130 °C) and feed moisture content (20–26%). Thirteen treatment combinations were generated for this experiment using a face-centered central composite design. Standard methods were used to evaluate the effect of barrel temperature and feed moisture content on extruded snacks' nutritional, anti-nutritional, physical, functional, and sensory acceptability. The data were analyzed, and processing conditions were optimized using the response surface methodology of Design Expert software version 13. Multiple regression analysis showed significant effects (p < 0.05) of the independent variables on moisture, protein, fat, beta-carotene, bulk density (BD), hardness, expansion ratio (ER), water absorption index (WAI), water solubility index (WSI), and overall acceptability of the extrudates. The optimum response of 14.06% protein, 3.26% ash, 69.12% carbohydrate, 6.477 mg/100 g beta-carotene, 0.36 g/ml bulk density, 2.72 Expansion ratio, 87.28 N hardness, 4.34 g/g Water absorption index, 22.34% Water solubility index, and overall acceptability of 3.30 was achieved at an optimal barrel temperature of 114.5 °C and feed moisture content of 20%. The obtained result suggests that barrel temperature and feed moisture content had a significant influence (p < 0.05) on the measured quality properties of the extrudates.

SURFACE ROUGHNESS OF Ti6Al4V ALLOY PRODUCED BY LASER POWDER BED FUSION

Controlling the surface roughness of materials manufactured by laser powder bed fusion (L-PBF) is critical for achieving functional performance of components and improving their mechanical properties. This is important for components whose surfaces cannot be post-treated using subtractive methods. In this study, the surface roughness has been investigated by applying different laser power and scanning speed combinations. Furthermore, potential effects of different locations on the build platform have been considered as well. The regression models have been developed using significant predictor variables, with their levels defined using face-centered central composite design. The analysis of variance (ANOVA) procedure has been used to evaluate the statistical significance of factors and model performances for each prediction variable. It has been found that the average surface roughness of L-PBF Ti6Al4V alloy can be described with high fitting accuracy using laser power and scanning speed as predictor variables. The position of specimens on the build platform showed no statistically significant effect on the average surface roughness. The experimental research and statistical analysis reported in this paper will contribute to a better understanding of how position, laser power, and scanning speed influence the average surface roughness of L-PBF Ti6Al4V alloy.

Bioactive extracts from grape (Vitis vinifera L. cv. País) leaves: Characterization and encapsulation in poly-3-hydroxybutyrate-co-3-valerate microparticles

Vitis vinifera var. L. País leaf extract, previously characterized, was microencapsulated by emulsion-solvent evaporation method using two different procedures: the conventional dropwise and micromixer device. The poly-3-hydroxybutyrate-co-3-hydroxyvalerate (PHBV) was used as encapsulating polymer. In addition, the effect of extraction time and ethanol:water ratio on the yield and the content of bioactive compounds of grape leaf extract obtained by Soxhlet method was determined using the face-centered central composite design. The highest bioactive compound were obtained using a 70:30 ethanol:water solvent ratio during 4 cycles. This extract is mainly composed of cinnamic acid, quercetin-3-glucoside and quercetin-3-glucorinide, containing 3.56, 2.08 and 1.19 mg g−1 extract, respectively. The total polyphenol content determined by Folin Ciocalteu method was 164 ± 14 mg GAE g−1 extract. The microparticles (2–3 μm) had spherical shape with rough and porous surface. The encapsulation efficiency was 15.1% and 60.6% for the PHBV microparticles prepared using conventional dropwise and micromixer device, respectively. The antioxidant activity present in the original extract was preserved around 50%–80% and 20%–70% in the loaded microparticles. The best results were achieved when grape leaf extract was encapsulated using micromixer device. The cell viability assay in 3T3-L1 fibroblasts, showed that loaded microparticles are not cytotoxic. In conclusion micromixer device showed to be effective for the microencapsulation of grape leaf extract using PHBV as encapsuling polymer.

Face-Centered Central Composite Design for the Optimization of the Extraction of Phenolic Compounds from Kernels and Shells of Raphia farinifera and Evaluation of the Antioxidant, Antimicrobial, and Anti-Inflammatory Activities

This study reports the extraction of phenolic compound from shells and kernels of the Raphia farinifera fruit and the biological activities of the extract. A face-centered composite design was established to optimize the extraction conditions: ethanol/water ratio (0-100%), solvent/powder ratio (10-30 mL/g), and extraction time (90-180 min). Subsequently, the extracts obtained under the optimal conditions were used for the evaluation of the radical scavenging capacity, the capacity to chelate ferric ions, and the antimicrobial and anti-inflammatory activities. The optimal extraction conditions for the shells are an extraction time of 134.24 min, 65% ethanol in water, and a solvent/substrate ratio of 21.16 mL/g, and for the kernel, an extraction time of 180 min, 94.3% ethanol in water, and a solvent/substrate ratio of 18.6 mL/g. In these conditions, the phenolic compounds were 95.36 mg EAG/L for the shell extract and 139.72 mg EAG/L for the kernel extract. The antioxidant activity revealed that the half-maximal inhibitory concentrations (IC50) of the kernel extracts are 22.32 μg/mL and 55.73 μg/mL for the shells. A reducing activity of Fe 3+ ions with an activity of 308.39 μg EAA/mg for the kernel extracts and 293 μg EAA/mg for the shells was observed. B. cereus was the most sensitive microorganism with a minimum inhibitory concentration (MIC) equal to the minimum bactericidal concentration (MBC) with a value of 156.25 ppm for the kernel extract while the shell extract showed MIC of 625 ppm and MBC of 2500 ppm. The IC50 values for the denaturation of proteins by extracts of shells and kernels are 0.76 μg/mL and 0.56 μg/mL, respectively. Membrane stabilization revealed IC50 values of 1054.54 μg/mL and 1339 μg/mL for the shell and kernel extracts, respectively. This work has shown the potential of Raphia farinifera extracts for the food industry and cosmetics.

Optimization of Hydrolysis Conditions, Isolation, and Identification of Biologically Active Peptides Derived from Acheta domesticus for Antioxidant and Collagenase Inhibition.

The study aimed to optimize hydrolysis conditions and isolate and identify bioactive peptides with anti-skin aging effects from Acheta domesticus (house cricket). A. domesticus proteins underwent hydrolysis using Alcalase® and optimized conditions using response surface methodology through a face-centered central composite design. Variable controls (enzyme-substrate concentration (E/S), time, and temperature) were assessed for their impact on activities against collagenase, 2,2-diphenyl-1-picrylhydrazyl radical (DPPH●), and degree of hydrolysis of protein hydrolysate (PH). PH was also investigated for composition, anti-skin aging, and anti-inflammatory effects. Amino acid sequences with potent anti-skin aging activity were isolated and identified using ultrafiltration, gel filtration chromatography, and liquid chromatography coupled with tandem mass spectrometry, employing de novo sequencing. Optimal conditions for producing PH with maximum anti-skin aging activity were an E/S concentration of 2.1% (w/w), 227 min, and 61.5 °C. Glutamic acid was a predominant amino acid and PH exhibited a molecular weight below 15 kDa. Additionally, PH displayed significant activities against collagenase, hyaluronidase, DPPH●, lipid peroxidation, and NF-κB-mediated inflammation (p < 0.05). Three novel anti-skin aging peptides were identified-Ala-Val-Thr-Lys-Ala-Asp-Pro-Tyr-Thr-Asp-Gln, Thr-Val-Met-Glu-Leu-Asn-Asp-Leu-Val-Lys-Ala-Phe, and Val-Pro-Leu-Leu-Glu-Pro-Trp-exhibiting the most potent collagenase and DPPH● inhibition. Therefore, this study proposed that PH, produced with Alcalase® under optimal conditions, emerges as a promising substance with potent anti-skin aging activity for the cosmeceutical industry.

Development and characterization of gelatin-based biodegradable films incorporated with pistachio shell hemicellulose

AbstractThis study aimed to incorporate pistachio shell hemicellulose into a film of gelatin and glycerol for the production of biodegradable films. The gelatin and glycerol are chosen because of their functional properties, which make it extensively used in food industry. The film composition was defined after a statistical optimization by central composite face-centered design and response surface methodology. The hemicellulose/gelatin ratio of 35.93% and the glycerol ratio of 18.02% were the optimum conditions to obtain lower film water solubility, higher tensile strength, and elongation at break values. The physical, structural, mechanical, and barrier properties of the developed hemicellulose-gelatin film were analyzed and compared with those of the gelatin film. Tensile strength and film water solubility values were reduced significantly with hemicellulose incorporation from 20.41 to 16.64 MPa and 49.57 to 39.21%, respectively, while EB was enhanced by 4.34 times. In addition, hemicellulose incorporation enhanced the water vapor permeability and the film degradation in the soil. The films were also examined by Fourier transform infrared spectroscopy and differential scanning calorimetry. The novelty of this study is to use pistcahio shell hemicellulose in the production of an edible film for the first time.

Optimization of hydrolases production by Penicillium crustosum in submerged fermentation using agro-waste residues as cosubstrate

This study aimed to enhance the production of exo-polygalacturonases (exo-PG), xylanases, and endoglucanases using Penicillium crustosum through submerged fermentation. Lemon peel (LP) and wheat bran (WB) were examined as potential cosubstrate for hydrolase production. The highest exo-PG and endoglucanase activities were observed with LP, whereas xylanase activity showed improvement with the addition of WB. To optimize exo-PG and endoglucanase production, a 23 Face-Centered Central Composite Design (FCCCD) was employed, varying crucial physicochemical factors. Similarly, a 24 FCCCD was utilized to optimize xylanase production by varying temperature, pH, MnSO4 concentration as a cofactor, and the PDB culture medium. Under optimized conditions, exo-PG production reached 1427.99 ± 27.41 U/mL, marking a 45% increase compared to initial fermentation conditions. Endoglucanase production peaked at 62.68 ± 9.65 U/mL under conditions of 45 °C, pH 5.5, and 2.5 g/L MnSO4. Xylanase production reached 271.77 ± 8.50 U/mL under optimal conditions (37.5 °C, pH 5.5, 2.5 g/L MnSO4, and 62.5% PDB). The optimized simultaneous production of the hydrolytic cocktail occurred at 45 °C, pH 5.5, and 2.5 g/L MnSO4 with LP, yielding maximum activities of 959.74 U/mL for exo-PG, 61.98 U/mL for endoglucanases, and 65.60 U/mL for xylanases as determined by FCCCD. In conclusion, Penicillium crustosum shows promise as a hydrolase producer, and the utilization of agro-wastes as cosubstrate enhances the yield of enzymes with industrial relevance.

Bionanofactory for green synthesis of collagen nanoparticles, characterization, optimization, in-vitro and in-vivo anticancer activities

Collagen nanoparticles (collagen-NPs) are promising biological polymer nanoparticles due to their exceptional biodegradability and biocompatibility. Collagen-NPs were bio-fabricated from pure marine collagen using the cell-free supernatant of a newly isolated strain, Streptomyces sp. strain NEAA-3. Streptomyces sp. strain NEAA-3 was identified as Streptomyces plicatus strain NEAA-3 based on its cultural, morphological, physiological properties and 16S rRNA sequence analysis. The sequence data has been deposited under accession number OR501412.1 in the GenBank database. The face-centered central composite design (FCCD) was used to improve collagen-NPs biosynthesis. The maximum yield of collagen-NPs was 9.33 mg/mL with a collagen concentration of 10 mg/mL, an initial pH of 7, an incubation time of 72 h, and a temperature of 35 °C. Using the desirability function approach, the collagen-NPs biosynthesis obtained after FCCD optimization (9.53 mg/mL) was 3.92 times more than the collagen-NPs biosynthesis obtained before optimization process (2.43 mg/mL). The TEM analysis of collagen-NPs revealed hollow sphere nanoscale particles with an average diameter of 33.15 ± 10.02 nm. FTIR spectra confirmed the functional groups of the collagen, collagen-NPs and the cell-free supernatant that are essential for the efficient capping of collagen-NPs. The biosynthesized collagen-NPs exhibited antioxidant activity and anticancer activity against HeP-G2, MCF-7 and HCT116 cell lines. Collagen-NPs assessed as an effective drug loading carrier with methotrexate (MTX), a chemotherapeutic agent. The TEM analysis revealed that the average size of MTX-loaded collagen-NPs was 35.4 ± 8.9 nm. The percentages of drug loading (DL%) and encapsulation efficiency (EE%) were respectively 22.67 and 45.81%.

Boundary Layer Stagnation Point Flow and Heat Transfer over a Nonlinear Stretching/Shrinking Sheet in Hybrid Carbon Nanotubes: Numerical Analysis and Response Surface Methodology under the Influence of Magnetohydrodynamics

The present study aims to offer new numerical solutions and optimisation strategies for the fluid flow and heat transfer behaviour at a stagnation point through a nonlinear sheet that is expanding or contracting in water-based hybrid nanofluids. Most hybrid nanofluids typically use metallic nanoparticles. However, we deliver a new approach by combining single- and multi-walled carbon nanotubes (SWCNTs-MWCNTs). The flow is presumptively steady, laminar, and surrounded by a constant temperature of the ambient and body walls. By using similarity variables, a model of partial differential equations (PDEs) with the magnetohydrodynamics (MHD) effect on the momentum equation is converted into a model of non-dimensional ordinary differential equations (ODEs). Then, the dimensionless first-order ODEs are solved numerically using the MATLAB R2022b bvp4C program. In order to explore the range of computational solutions and physical quantities, several dimensionless variables are manipulated, including the magnetic parameter, the stretching/shrinking parameter, and the volume fraction parameters of hybrid and mono carbon nanotubes. To enhance the originality and effectiveness of this study for practical applications, we optimise the heat transfer coefficient via the response surface methodology (RSM). We apply a face-centred central composite design (CCF) and perform the CCF using Minitab. All of our findings are presented and illustrated in tabular and graphic form. We have made notable contributions in the disciplines of mathematical analysis and fluid dynamics. From our observations, we find that multiple solutions appear when the magnetic parameter is less than 1. We also detect double solutions in the shrinking region. Furthermore, the increase in the magnetic parameter and SWCNTs-MWCNTs volume fraction parameter increases both the skin friction coefficient and the local Nusselt number. To compare the performance of hybrid nanofluids and mono nanofluids, we note that hybrid nanofluids work better than single nanofluids both in skin friction and heat transfer coefficients.

Application of Response Surface Methodology Using Face-centered Central Composite Design for Studying Long-Term Stability of Gliclazide-Loaded Multiparticulate Systems

The appropriate design of experiments (DoE) could support post-approval lean-stability approaches. A three-factor three-level face-centered design was constructed to evaluate the long-term stability of gliclazide (GLZ) alginate-gelatin beads. The formulation variables were GLZ%(X1), alginate:gelatin ratio(X2), and glutaraldehyde%(X3). The studied responses included GLZ release at predefined intervals in 0.1 N HCl (2 h) followed by phosphate buffer (pH 7.4). Model-dependent and independent approaches were utilized for comparison. DoE-model validation and reduction were implemented. All the studied formulations showed non-significant changes in the particle size (p > 0.05) and most of them showed similar release profiles before and after storage. The directions of the relationships between the factors' main effects and the responses (Y1:Q0.5h, Y2:Q2h, and Y3:Q4h) remained unchanged after storage. The optimal factor settings based on the proposed optimization criteria were defined. The optimized formulations (OP-1 and OP-2) showed non-significant changes in the particle size after storage. The release profiles and kinetics of OP-1 and OP-2 remained unchanged after storage. No chemical change was indicated (FT-IR). DSC-thermograms of OP-1 indicated GLZ conversion to a more stable polymorph after storage. While OP-2 showed a change in GLZ crystallinity. The stored and fresh beads’ surfaces after GLZ release were almost similar. DoE could be utilized to evaluate, optimize, and predict the effects of different formulation variables on the long-term stability of GLZ alginate-gelatin beads.

Optimization bio-oil production from Chlorella sp. through microwave-assisted pyrolysis using response surface methodology

Optimization can streamline experimental trials by evaluating the parameters and parameter interactions used as the basis for a more optimal downstream process. This study aims to optimize the microwave-assisted pyrolysis process in producing bio-oil from microalgae using response surface methodology (RSM) complemented by an investigation of the reaction mechanisms. A number of key parameters (microwave power, absorbent-to-microalgae ratio, and pyrolysis time) were fine-tuned using a face-centered central composite design. The result showed that microwave technology in slow pyrolysis could produce the bio-oil from microalgae 12 times shorter than conventional heating and quadratic model with a high precision (R2 = 0.9832, R2adj = 0.9616) from RSM optimization in predicting experimental values yielded a peak bio-oil yield of 19.11% under specific conditions: 20 min of pyrolysis time, a 0.19 (w/w) microwave absorber to microalgae ratio, and 583 W power. As the complex biomass, the reaction mechanism in chlorella sp. towards this technology including decarboxylation, decarbonylation, dehydration, cracking, deoxygenation, and esterification was proved in GCMS analysis, revealing the presence of key functional groups such as aliphatic, aromatics, alcohols, nitrogenous compounds, fatty acid methyl esters (FAME) and Polycyclic Aromatics Hydrocarbons (PAHs).

Fretting wear characteristics of Ti6Al4V/TiC nano composites using response surface method

This study explores the impact of titanium carbide (TiC) nanoparticles on the microstructure and fretting wear performance of Ti64-GV alloys. The Ti64 alloys, featuring varying TiC concentrations, were fabricated through spark plasma sintering (SPS) process. Fretting experiments followed a face-centered central composite design methodology, employing a second-order quadratic regression model to analyze wear volume loss and coefficient of friction (CoF). The findings revealed a notable reduction in wear volume loss and friction coefficient with increasing TiC content. The presence of TiC significantly enhanced the wear resistance of Nano-composites due to heightened hardness and oxidation wear resistance. Employing hybrid desirability-based response surface methodology (RSM) led to substantial improvements in wear characteristics (37% in CoF and 46% in wear volume loss). Microstructural analysis affirmed enhanced surface quality and textures using the RSM hybrid approach for predicting optimal process parameters.

NUMERICAL MODEL FOR OPTIMIZING THE PARAMETERS FOR LASER-BEAM WELDING OF A HIGH-TEMPERATURE MATERIAL

Ferritic stainless steel (FSS) is one of the high-temperature materials, used in many industries for sustainable applications such as power plants, automotive, offshore and chemical industries. Joining these materials is challenging due to the formation of an intermetallic and the grain growth with high-heat-input welding methods. Laser beam welding (LBW) that uses a low heat input was used successfully to join AISI 409 FSS tubes. In this work the welding speed and focal distance were varied as per a two-factor, three-level face-centred central composite design (FCCCD) to join AISI 409 FSS. A numerical model was developed to correlate the relationship between the ultimate tensile strength (UTS) and LBW process parameters. The validation of the developed model was carried out using the analysis of variance. Both welding speed and focal distance have a significant effect on determining the UTS. The optimised process parameters provided for a better UTS as reported in this paper.

Statistical Design-Guided Synthesis of Nanoarchitectonics of High-Performance NiFeMoN Electrocatalyst through Facile One-Step Magnetron Sputtering.

This study presents an innovative, statistically-guided magnetron sputtering technique for creating nanoarchitectonics of high-performing, NiFeMoN electrocatalysts for oxygen evolution reaction (OER) in water splitting. Using a central composite face-centered (CCF) design, 13 experimental conditions are identified that enable precise optimization of synthesis parameters through response surface methodology (RSM), confirmed by analysis of variance (ANOVA). The statistical analysis highlighted a interaction between Mo% and N% in the nanostructured NiFeMoN and found optimizing values at 31.35% Mo and 47.12% N. The NiFeMoN catalyst demonstrated superior performance with a low overpotential of 216mV at 10mA cm-2 and remarkable stability over seven days, attributed to the modifications in electronic structure and the creation of new active sites through Mo and N additions. Furthermore, the NiFeMoN coating, when used as a protective layer for a Si photoanode in 1m KOH, achieved an applied-bias photon-to-current efficiency (ABPE) of 5.2%, maintaining stability for 76 h. These advancements underscore the profound potential of employing statistical design for optimizing synthesis parameters of intricate catalyst materials via magnetron sputtering, paving the way for accelerated advancements in water splitting technologies and also in other energy conversion systems, such as nitrogen reduction and CO2 conversion.

Multi-objective optimization of simultaneous oxidative desulfurization and denitrogenation of model fuel

Petroleum fractions are accompanied with sulfur and nitrogen compounds, and nitrogen compounds tend to compete for the catalyst active sites, reducing desulfurization efficiency. They can be removed by oxidative desulfurization and denitrogenation, wherein the sulfur and nitrogen compounds are converted into corresponding oxides with higher polarity than their parent forms, thus favoring their extractive or adsorptive removal from the oil phase. The introduction of ultrasound into the oxidation system can significantly improve the process efficiency and oxidation kinetics through strong cavitation phenomena involving physical and chemical effects. In this work, ultrasound-assisted simultaneous oxidation of pyridine and dibenzothiophene (DBT) contained in a model fuel was performed. Response surface methodology (RSM) was employed to study the effect of six parameters, viz., catalyst dose (5–12.5 g/L), reaction time (5–60 min), ultrasonic amplitude (10–60 %), volume of hydrogen peroxide (0.5–2 mL), volume of acetic acid (0.5–2 mL) and reaction temperature (40–60 °C) on the conversion of DBT and pyridine. A face-centered central composite design was employed as the RSM tool, and the effect of the parameters and their interactions on the two responses was investigated. The two responses were simultaneously optimized via desirability functions and overlaying individual contour plots. The results revealed that sonication significantly enhanced the conversion of both compounds. All six factors significantly influenced the oxidation of pyridine, while DBT conversion was mainly affected by four factors. The desirability for the process under consideration ranged from 0.85 to 0.89, and at the optimum conditions, 100 % conversion of pyridine and 46.06 % conversion of DBT were obtained. Two-staged oxidation of the fuel at optimum conditions resulted in 100 and 93.7 % conversion of pyridine and DBT, respectively.

A Cyanoalkyl Silicone GC Stationary-Phase Polymer as an Extractant for Dispersive Liquid–Liquid Microextraction

In this work, three cyanoalkyl silicone GC stationary-phase polymers, namely OV-105, OV-225, and OV-275, were investigated as potential extractants for dispersive liquid–liquid microextraction (DLLME). The OV-225 polymer (cyanopropylmethyl-phenylmethylsilicone) exhibited the cleanest chromatographic background and was extensively studied. The proposed polymer was tested through the DLLME of four non-steroidal anti-inflammatory drugs from aqueous samples, followed by HPLC separation with UV detection at 230 nm. To achieve the maximum enrichment, the experimental conditions that influence the DLLME process were optimized using one-factor-at-a-time and design-of-experiment (DoE) approaches. The extraction variables (polymer mass, dispersive solvent volume, buffer pH, and mixing time) were screened by implementing a two-level full factorial design (FFD). Significant variables were fine-tuned using response surface methodology based on a face-centered central composite design (CCD). The optimum conditions were 10 mg of polymer (extraction medium); 50 µL of tetrahydrofuran (dispersive solvent); 100 µL of phosphate buffer pH 2.75 ([PO43−] = 100 mM); and 3 min of vortex mixing. The addition of salt had a minimal effect on the enrichment factors. In the optimum conditions, enrichment factors up to 46 were achieved using 1.5 mL samples. Calibration curves exhibited correlation coefficients &gt; 0.999 using 4-pentylbenzoic acid as an internal standard. The limits of quantitation were 5 ng/mL for naproxen, 10 ng/mL for diflunisal, 25 ng/mL for indomethacin, and 75 ng/mL for ibuprofen. The analysis of spiked tap water samples showed adequate relative recoveries and precision. In conclusion, the proposed polymer (OV-225) is a potential greener alternative to traditional organic extractants used in DLLME.

Optimization of HPMC-Based Oral Fast Dissolving Film of Cetirizine Dihydrochloride

There are challenges involved in improving the convenience of cetirizine dihydrochloride (CTZ) administration for geriatric and pediatric patients with allergic asthma. Due to the ease of swallowing, oral fast-dissolving films (OFDFs) have been identified as a potential solution. This study aimed to prepare hydroxypropyl methylcellulose (HPMC)-based OFDFs of CTZ using the solvent casting method. Film compositions, including the amounts of HPMC and glycerin, were optimized using a face-centered central composite design based on film thickness, folding endurance (FE), and disintegration time (DT). Nine prepared films were found to be transparent and clear in appearance, demonstrating the homogeneity of the films. The weights and thicknesses of all films were in the ranges of 57-109 mg and 22 - 40 µm. The FE of the prepared films was determined to be 42-156, 30-124, and 17-70 times for 3%, 4%, and 5% (w/w) HPMC-based films, respectively. The DT of the films ranged from 99 ± 13 to 478 ± 21 s as their compositions were altered in terms of the HPMC contents and the amount of glycerin. The film fabricated from 3 % (w/w) HPMC and 10% (w/w polymer mass) glycerin (F3) was identified as optimal due to achieving the highest FE and the least DT. Moreover, regression analysis demonstrated a significant effect of the HPMC and glycerin amounts on the film properties. After adding CTZ in F3 (the optimized film), the CTZ content in the films was 0.84 ± 0.14 mg/cm2. The optimized film could be evaluated further for drug release and drug permeation. Keywords: Cetirizine dihydrochloride, Film former, Folding endurance, HPMC-based film, Plasticizer

Optimization of photofermentative biohydrogen production in a mixed volatile fatty acid medium by Rhodobacter sp. MAY2: A response surface methodology (RSM) approach

Biohydrogen production through photofermentation has gained significant attention as it provides a sustainable solution for clean energy supply and addresses wastewater concerns by utilizing volatile fatty acids (VFA) which are produced in dark fermentation. In this study, response surface methodology via a Face-centered Central Composite Design (FCCD) was employed to optimize buffer solution pH, ferric citrate concentration, sodium glutamate concentration to maximize biohydrogen production by Rhodobacter sp. MAY2 with mixed VFA (acetate, propionate, butyrate) as substrates. Results showed that the concentrations of ferric citrate, sodium glutamate, and buffer solution pH positively impact the biohydrogen production of Rhodobacter sp. MAY2. The optimal conditions were shown to be 0.36 mM ferric citrate, 11 mM sodium glutamate, and buffer solution of pH 7. The predicted hydrogen production potential (HPP) at these conditions (661.1 mL/L) was within 2 % of the actual HPP (647.7 mL/L). Kinetic parameters using the modified Gompertz equation showed that the predicted values for maximum potential cumulative H2 production (P), maximum hydrogen production rate (Rm), and lag time (λ) are comparable to those reported in literature. Overall, the study highlighted the potential of a local isolate, Rhodobacter sp. MAY2, for biohydrogen production and the suitable fermentation conditions for its growth.