Plackett-Burman Factorial Design Research Articles

Evaluation of hydrocyclonage variables aiming at the optimization of the processing of kaolin of the primary type

Kaolin is a white rock, formed basically by the clay mineral kaolinite, for presenting favorable technological characteristics has a wide industrial application. Kaolin deposits are classified geologically into two types according to their origin: primary and secondary. Kaolin from the Seridó region of Paraíba and Rio Grande do Norte is of the primary type and its processing is carried out wet, generating two types of tailings. It is considered a difficulty in the current processing of this kaolin the method of mineral classification that is carried out by vibratory sieves. The main objective of this work was to evaluate the variables that influence the hydroclinage process for the classification of kaolin of the primary type. The trials were performed on a bench scale, using the Plackett-Burman factorial design. The best results were found in the T4 and T6 tests, which presented lower values of D50 and the results of XRF indicated that the aluminum oxide contents are higher in the overflow and the silica contents higher in the underflow. The trials indicated promising results for the classification of this type of kaolin, but a good adjustment of the operational variables is needed.

Air-assisted liquid-liquid microextraction and enantioselective gas chromatography-tandem mass spectrometry quantification of methyl jasmonate stereoisomers in tea (Camellia sinensis L.)

Different stereoisomers of phytohormones may have different roles in plants while the quantification for stereoisomers still remains a challenge. The chiral separation method for methyl jasmonate (MeJA) in tea (Camellia sinensis L.) was developed by air-assisted liquid-liquid microextraction (AALLME) with enantioselective gas chromatography-mass spectrometry (Es-GC-MS/MS). The Plackett-Burman factorial design was introduced to optimize the multiple parameters of AALLME. Sensitive Es-GC-MS/MS enabled the quantification of the MeJA stereoisomers, which were separated from each other with resolutions of 3.5, 2.7, and 2.5. The linearities were R2 > 0.9971, the limits of detection were 0.08–0.12 ng/mL, the limits of quantification (LOD) were 0.28–0.39 ng/mL, and the recovery range was 80.60–107.03%. The method was applied to analyze the MeJA stereoisomer profiles in tea plants after geometrid feeding and mechanical wounding. (+)-MeJA appeared to be the main bio-active monomer that responded to injury stress. (+)-MeJA similarly increased in tea shoots at only 30 s after geometrid attack or mechanical wounding. The proposed method is superior as air-assisted liquid-liquid microextraction could induce the loss of volatile MeJA in a much shorter time, compared to the conventional enrichment procedure. A novel assay protocol for relative quantification of MeJA stereoisomers in plants responding to different injuries was applied.

Lipase from Fusarium solani: optimization of culture conditions, biochemical properties, and production

A Plackett-Burman factorial design with 15 experiments was conducted to evaluate the influence of seven factors on lipases production by Fusarium solani. The factors investigated were peptone, tryptone, yeast extract, calcium chloride, potassium phosphate, magnesium sulfate, and copper sulphate. Five fixed variables (cotton oil, pH, temperature, agitation, and time) were maintained and as a response to the enzymatic activity. The concentration of tryptone, calcium chloride, and magnesium sulphate had a significant effect (p < 0.10) on lipase production and was studied consecutively through a complete DCCR (central rotational compound design), to optimize lipase production of the fungi F. solani. After optimization using DCCR, maximum lipolytic activities of 24.84 U/ml were obtained with the use of 10 g.L-1 tryptone, 3.50 g.L-1 calcium chloride and 0.50 g.L-1 magnesium sulfate, 1 g.L-1 potassium phosphate and 1% soybean oil. The statistical model showed a correlation of 85.67% with the experimental data. The biochemical characterization of lipase showed that the enzyme has a better performance at pH 7 at a temperature of 40 °C, where the statistical model had a correlation of 94.15% with the experimental data. In this way, lipases produced by F. solani have potential for application and use in biodiesel production.

Chemometric approaches for the optimization of headspace-solid phase microextraction to analyze volatile compounds in coriander (Coriandrum sativum L.)

Headspace-solid phase microextraction (HS-SPME) conditions for the gas chromatography-mass spectrometry (GC-MS) analysis of volatiles in coriander aerial part were systematically optimized for the first time using chemometric approaches. Single factor test preliminarily determined the superior level of each parameter. Plackett-Burman factorial design further identified the three most significant variables (heating temperature > extraction time > CaCl2 amount). Then, Box-Behnken design of response surface methodology (RSM) was applied to obtain the optimal extraction conditions and corresponding model equation (R2 = 0.9793–0.9809). Verification results with less than 5% of relative standard deviations (RSDs) indicated that this extraction procedure had good repeatability and intermediate precision. A total of 67 volatiles were identified from coriander, mainly including aldehydes, alcohols, hydrocarbons and esters. Among them, the proportion of aldehydes was highest approximately 83.76%, and (E)-2-tetradecenal was the most abundant analyte, followed by (Z)-9-hexadecenal, 2-dodecenal and (E)-2-tridecenal. There were 21 characteristic volatiles with the odor activity values (OAVs) greater than 1, which contributed greatly to coriander flavor. Moreover, citrus aroma was the strongest scent, afterwards were fatty and unpleasant soapy odors. This research provided an advanced technical support for the extraction and analysis of coriander volatiles.

Growth Optimization and Secondary Metabolites Evaluation of Anabaena variabilis for Acetylcholinesterase Inhibition Activity.

Cyanobacteria comprise a good natural resource of a potential variety of neuro-chemicals, including acetylcholinesterase inhibitors essential for Alzheimer’s disease treatment. Accordingly, eight different cyanobacterial species were isolated, identified, and evaluated on their growth on different standard nutrient media. It was found that the modified Navicula medium supported the highest growth of the test cyanobacteria. The effects of methylene chloride/methanol crude extracts of the test cyanobacteria on acetylcholinesterase activity were examined and compared. Anabaena variabilis (KU696637.1) crude extract recorded the highest acetylcholinesterase inhibition (62 ± 1.3%). Navicula medium chemical components were optimized through a Plackett–Burman factorial design. The biomass of Anabaena variabilis increased significantly when grown on the optimized medium compared to that of control. The chemical analysis of the fractions derived from Anabaena variabilis showed the presence of two compounds in significant amounts: the flavonoid 5,7-dihydroxy-2-phenyl-4H-chrome-4-one and the alkaloid 4-phenyl-2-(pyridin-3-yl) quinazoline. Molecular docking studies revealed that both compounds interact with the allosteric binding site of acetylcholinesterase at the periphery with π-π stackings with Tyr341 and Trp286 with good, predicted partition coefficient. The compounds obtained from this study open the door for promising drug candidates to treat Alzheimer’s disease for their better pharmacodynamics and pharmacokinetic properties.

Lead biosorption by magnetic Pisum sativum peel biocomposite using experimental design

ABSTRACT The Pisum sativum has been used as a magnetic biocomposite biosorbent for the removal of lead ions from aqueous solutions. These biocomposites were prepared with encapsulated alginate beads into calcium chloride solution, Pisum sativum peel powder and iron (II–III) oxide. Properties of surface and the possible binding sites of the material were evaluated by instrumental analysis using Fourier transform infrared spectroscopy-attenuated total reflection, scanning electron microscope, and X-ray diffraction. Scanning electron microscopy–energy-dispersive X-ray spectroscopy and mapping techniques are also used for evaluation of process. Optimisation of biosorption procedure was done by Plackett–Burman factorial design including parameters such as biocomposite amount, pH, temperature and extraction time. The analytical performance of the biosorption method, application to industrial effluent, the reusability and stability of biosorbent were also investigated. The Pisum sativum magnetic biocomposite adsorbed 90 ± 4% of lead at the optimum pH value 4 and 125 mg biocomposite amount. The best-fitting isotherm model is Freundlich and theoretical capacity of biosorbent was calculated as 74.05 mg/g. The report of magnetic Pisum sativum biocomposite as a biosorbent may be used as natural renewable resources and reduces the adverse effects on water contaminated for lead.

Optimization and Evaluation of the In Vitro Permeation Parameters of Topical Products with Non-Steroidal Anti-Inflammatory Drugs through Strat-M® Membrane.

Pharmaceutical products containing non-steroidal anti-inflammatory drugs (NSAIDs) are among the most prescribed topical formulations used for analgesic and antirheumatic properties. These drugs must overcome the skin barrier to cause a therapeutic effect. Human skin has been widely used as a model to study in vitro drug diffusion and permeation, however, it suffers from many limitations. Therefore, to perform in vitro permeation test (IVPT), we used a Strat-M® membrane with diffusion characteristics well-correlated to human skin. This study’s objective was to optimize the IVPT conditions using Plackett–Burman experimental design for bio-predictive evaluation of the in vitro permeation rates of five non-steroidal anti-inflammatory drugs (diclofenac, etofenamate, ibuprofen, ketoprofen, naproxen) across Strat-M® membrane from commercial topical formulations. The Plackett–Burman factorial design was used to screen the effect of seven factors in eight runs with one additional center point. This tool allowed us to set the sensitive and discriminative IVPT final conditions that can appropriately characterize the NSAIDs formulations. The permeation rate of etofenamate (ETF) across the Strat-M® membrane was 1.7–14.8 times faster than other NSAIDs from selected semisolids but 1.6 times slower than the ETF spray formulation.

Optimal Design of Flexspline in New Modular Robotic Joints Considering Position Keeping Conditions

In order to improve the service life of modular joints and meet the requirements of compact structure, considering the position keeping conditions of modular joints, a multi-objective optimization design method for the maximum stress and tube length of the new modular joint flexspline was proposed. This method established a finite element analysis model based on a new modular joint structure, conducted a thermo-mechanical coupling analysis on the joint under the holding state, and obtained the stress distribution of the flexible wheel. Plackett-Burman factorial design was used to screen the significant factors that affect the maximum stress. Based on the Box-Behnken test method and the least square method, the second-order response surface approximate model of the maximum stress of the flexspline was established. Taking the geometric structure parameters of the harmonic drive components as the design variables, and the maximum stress and tube length of the flexspline as the design goals, the response surface approximate model is optimized through the multi-objective genetic algorithm. The optimization calculation example of the new modular joint shows that the method can reduce the maximum stress of the flexspline while reducing the tube length, achieving the purpose of reducing the joint volume and increasing the service life.

Statistical optimisation for enhancement of phenol biodegradation by the Antarctic soil bacterium Arthrobacter sp. strain AQ5-15 using response surface methodology

Aim: Effective bioremediation requires optimisation of conditions under which the process takes place. In this study, an Antarctic soil bacterium, Arthrobacter sp. strain AQ5-15, was evaluated for phenol biodegradation under statistically optimised conditions. Methodology: The composition of degradation media and the culture conditions for this study were determined according to the experimental requirements obtained from Plackett-Burman factorial design (PB) and Box-Wilson Central Composite Design (CCD), respectively. Phenol degradation was monitored by 4-aminoantipyrine colorimetric assay and bacterial growth was quantified by measuring optical density (OD600 nm) at 72 hr. Results: A preliminary screening experiment using the Plackett-Burman design indicated that all the factors screened (ammonium sulphate concentration, sodium chloride concentration, pH and temperature) had significant influence on degradation performance. Response Surface Methodology was then utilised to further optimise the phenol-degrading process using Central Composite Design. The maximum percentage of phenol degradation achieved with CCD was 99.42%, under medium conditions of 0.15 g l-1 (NH4)2SO4, 0.13 g l-1 NaCl, pH 7.25 and incubation at 15°C for 72 hr. The strain could degrade phenol when exposed to an initial concentration of up to 1.5 g l-1 under these optimised conditions. Interpretation: The tolerance and degradation characteristics of strain AQ5-15 suggest that it has potential application in bioremediation of polluted sites and in the treatment of relatively cool water bodies contaminated with phenol.

Malathion determination in Rice samples with Graphene oxide reinforced hollow fiber-solid phase microextraction by GC-MASS

A method for applicability of the solid phase microextraction (SPME) procedure for determination of trace amounts of the organophosphorus pesticide malathion by gas chromatography - mass spectrometry (GC-MS) was developed. Graphene oxide reinforced sol–gel which was placed in hollow fiber (HF-SPME) was used for pre-concentration of malathion. In the present study the Plackett-Burman (PB) factorial design was used as a method for first monitoring of Eight factors that have a significant impact and optimized them in next stage, optimization process of significant factor was carried out using a five-level CCD after screening by PBD. the following conditions were selected for the analytical method of Malathion in real sample: amount of GO (0.01gr), pH of aqueous solution (pH: 3), volume of aqueous solution (10000 µl), volume of organic solvent (250 µl), adsorption time (35 min), desorption time (30 min), stirring rate of solution (1000 rpm) and amount of salt (4%). Calibration curves were plotted using three spiking levels of malathion in the concentration ranges of 0.2–0.4-0.5 ng/mL with correlation coefficients (r 2 ) 0.9914 for analytes. Under the optimized extraction conditions, the method showed good linearity (0.05–0.5 ng/mL), repeatability, low limits of detections (3.9×10 -3 ng/mL) and excellent pre-concentration factors (4000). The optimum conditions which were evaluated then applied for the analysis of malathion in the rice as a real sample

Application of poly(vinyl alcohol)-assisted silver nanoparticles immobilized β-keratinase composite as topical antibacterial and dehairing agent

For developing an environmentally friendly, antibacterial, dehairing topical formulation, a β-keratinase enzyme (20.1 kDa) purified from Bacillus subtilis strain RM-01 was coupled to silver nanoparticles(AgNPs) of 8.0 ± 2.0 nm dimensions, prepared using poly(vinyl alcohol) matrix. The Plackett–Burman factorial design demonstrated that the pH of the buffer, amount of silver nanoparticles (Ag NPs), and concentration of β-keratinase enzyme play the most significant role in the Ag NP-enzyme-binding process. Biophysical techniques using scanning electron microscope, transmission electron microscope, X-ray diffraction, and Fourier-transform infrared spectroscopy (FT-IR) were used to characterize the free Ag NPs as well as AgNPs immobilized by β-keratinase. Binding of β-keratinase to Ag NPs resulted in a 5.6-fold increase in specific activity, a considerable increase in Vmax with a corresponding decrease in Km values towards keratin, and a significant improvement of the thermal and storage stabilities of immobilized enzyme compared to free enzyme. The enhanced antibacterial potency, dehairing activity, and organoleptic analysis of AgNPs immobilized with β-keratinase supports the industrial application of β-keratinase-immobilized Ag NPs in the pharmaceutical and cosmetic industries.

Bio-Waste Aloe vera Leaves as an Efficient Adsorbent for Titan Yellow from Wastewater: Structuring of a Novel Adsorbent Using Plackett-Burman Factorial Design

Titan yellow (TY), a triazene azo dye, was removed from contaminated wastewater samples using a green adsorbent recycled from Aloe vera leaves (AV) waste. Two adsorbents were developed—air-dried Aloe vera (ADAV) and thermally treated Aloe vera (TTAV). Adsorption efficacy of both adsorbents was assessed in terms of percent removal (%R) of TY and adsorption capacity (qe). ADAV had a better performance compared to TTAV. Plackett–Burman design (PBD) was exploited to establish the experimental pattern of the study. Four variables were studied: pH, adsorbent dose (AD), dye concentration (DC), and stirring time (ST). Analysis of variance (ANOVA) at 95.0 confidence interval (CI), control, and quality charts helped establish regression model(s). Characterization of both adsorbents was performed using FT-IR/Raman spectroscopy together with TGA/dTGA and SEM/energy dispersive X-ray spectroscopy (EDX) analyses. Textural properties were determined using nitrogen adsorption isotherms at 77 K. Results showed that the surface areas of ADAV and TTAV300 were 3.940 and 7.076 m2/g, respectively. Raman analysis showed that the TTAV had clear D- and G-bands. Equilibrium studies revealed that data were well fitted to Freundlich isotherm with a maximum adsorption capacity of 55.25 mg/g using Langmuir equation, and the adsorption was physisorption. Adsorption followed a pseudo-second order that occurred in two steps—diffusion and then adsorption.

Optimization of total phenol and anthocyanin extraction from the peels of eggplant (Solanum melongena L.) and biological activity of the extracts

Anthocyanins are biologically active compounds with high antioxidant capacity, found in many fruits and vegetables. In this study, optimizations of total anthocyanin (TA) and total phenolic content (TPC) in the extracts from peels of Solanum melongena L. (eggplant) were investigated by considering eight independent variables including: alcoholic solvent type (methanol or ethanol), volume ratio of alcohol to water, acid type (acetic acid or hydrochloric acid), acid volume, ratio of solid mass to solvent volume (w/v), particle size of solid, temperature and extraction time. Effects of these variables on the extraction yields were investigated using Plackett–Burman factorial design with sixteen experimental runs. Results indicated that the ratio of solid mass to liquid volume and temperature had significant positive effects on the total extraction yield, while the solvent volume ratio showed significant negative effect. Acid volume ratio, temperature and time improved independently anthocyanins extraction yield, while temperature and acid volume ratio had significant positive effects on the extraction yield of phenolic contents. Statistical analysis showed that temperature influenced most significantly both TA and TPC response variables. Maximum TA yield recorded was about 431.58 mg/100 g dry (in conjunction with highest TPC yield), and biological tests carried out for this anthocyanin-rich extract, showed potent antioxidative properties (IC50 of 11.23 ± 1) compared to BHT (IC50 of 16.54 ± 0.07) and β-carotene oxidation being effectively inhibited (88.37 ± 1.21% inhibition). In-vitro cytotoxicity of the sample was also evaluated against brine shrimp larvae and human breast cancer cells with LC50 of 125 µg/mL and growth inhibition percentage of 80%, respectively.

Tailored functionalized polymer nanoparticles using gamma radiation for selected adsorption of barium and strontium in oilfield wastewater

To improve oil recovery from oilfield wells mineral scales derived by insoluble BaSO4 and SrSO4 salts during oil extraction should be diminished. In this work, adsorption selectivity of Barium (Ba2+) and Strontium (Sr2+) ions associated with saline formation waters was examined for the first time using nano-sized bi-functional polymer blend synthesized by Cobalt-60 (60Co) γ-rays, as green technology. A bifunctional polymer formed from poly(acrylonitrile)/(styrene-butadiene rubber) homogenous blend is functionalized by -SO3H and -COOH terminal groups (termed as SASB). Those functional groups were selected based on systematic calcium (Ca2+) ions adsorption studies of carboxylate containing molecules. Main and binary interactive effects of solution pH (3–9), adsorbents dose (1-3 g/L), total dissolved salts (TDS, up to 30 g/L), initial Ba2+ and Sr2+ concentrations (10-500 mg/L) and temperature (20–50 oC) on the adsorption selectivity were examined and optimized using Plackett-Burman factorial design (PBD) combined with multiple regression analysis. The regression statistics revealed the significance of quadratic polynomial model to optimize interactive sorption conditions from salty waters with high accuracy level (R2≈ 0.99) rather than linear and two-way interactive models at 95% confidence level. Interestingly finding, the regression and experimental data proved that the presence of up to 10 g/L TDS from alkali metal ions had a significant effect on the enhancement sorption capacity of Ba2+ and Sr2+ when using the prepared sorbent. The SASB adsorbent showed higher sorption selectivity with maximum equilibrium capacity (qmg/g) of 175.3 mg Ba+2 and 210.5 mg Sr+2 per each gram sorbent used in kinetic study. Adsorption kinetics of Ba2+ and Sr2+ sorption by both adsorbents obey pseudo-first and pseudo-second order kinetics, respectively. In sum, the adsorptive power of SASB sorbent is found to be in reverse order of the electronegativity and the hydration radii of the metal ions.

Isolation and characterization of a marine testosterone-degrading bacterium: Vibrio sp. N3

Steroids, including testosterone, estrone, 17β-estradiol, estriol and 17β-ethinyl estradiol, are harmful not only to the population dynamics of aquatic life forms but also to public health. In this study, a marine testosterone-degrading bacterium (strain N3) was isolated from Nanao Island in the South China Sea. In addition, the strain could also use 17β-estradiol (E2), 17β-ethinyl estradiol (EE2), estriol (E3) or cholesterol as a sole carbon source. According to the 16S rRNA gene sequence analysis, strain N3 was identified as Vibrio sp. Further characterization showed that the strain is aerobic, gram-negative, and mobile and exhibits resistance to ampicillin, carbenicillin, penicillin and spectinomycin. For enhancing its capacity of testosterone degradation, the Plackett–Burman factorial design and the central composite design were used to optimize the culture condition. Under optimal conditions, 92% of testosterone was degraded by Vibrio sp. N3 in 48h.

Isolation, characterisation and efficacy of the bacterial strain Lysinibacillus sphaericus YMM in biodegradation of malathion insecticide in liquid media

ABSTRACT A new isolate of bacterium Lysinibacillus sphaericus YMM capable of degrading malathion insecticide in liquid media was isolated and characterised. Biodegradation factors were investigated using Plackett–Burman factorial design, and the rest of the insecticide was monitored by high-performance liquid chromatography analysis. The near optimum conditions for degradation of 200 mg malathion/L were 30 mL medium, 2% of L. sphaericus suspension (0.70 OD600nm), pH 5,10 g/L glucose, 1.0 g/L NaCl, 0.3 g/L MgSO4, 1.0 g/L NH4Cl and incubation for 24 h without yeast extract and peptone or beef extract. In addition, the significant variables including the medium volume, inoculum and incubation time were further optimised using Box–Behnken response surface design. These conditions were found to be 30.10% medium and inoculum of 0.706 (OD600nm) for 23.636 h of incubation to achieve 98.974% degradation. Therefore, L. sphaericus YMM showed a potential degradation of malathion. Further studies should be conducted to understand the mechanism of biodegradation in liquid media.

Biosorption optimization, characterization, immobilization and application of Gelidium amansii biomass for complete Pb2+ removal from aqueous solutions

Lead (Pb2+) is among the most toxic heavy metals even in low concentration and cause toxicity to human’s health and other forms of life. It is released into the environment through different industrial activities. The biosorption of Pb2+ from aqueous solutions by biomass of commonly available, marine alga Gelidium amansii was studied. The effects of different variables on Pb2+ removal were estimated by a two-level Plackett–Burman factorial design to determine the most significant variables affecting Pb2+ removal % from aqueous solutions. Initial pH, Pb2+ concentration and temperature were the most significant factors affecting Pb2+ removal chosen for further optimization using rotatable central composite design. The maximum removal percentage (100%) of Pb2+ from aqueous solution by Gelidium amansii biomass was found under the optimum conditions: initial Pb2+ concentration of 200 mg/L, temperature 45 °C, pH 4.5, Gelidium amansii biomass of 1 g/L and contact time of 60 minutes at static condition. FTIR analysis of algal biomass revealed the presence of carbonyl, methylene, phosphate, carbonate and phenolic groups, which are involved in the Pb2+ ions biosorption process. SEM analysis demonstrates the ability of Gelidium amansii biomass to adsorb and removes Pb2+ from aqueous solution. EDS analysis shows the additional optical absorption peak corresponding to the Pb2+ which confirms the involvement of Gelidium amansii biomass in the adsorption of Pb2+ ions from aqueous solution. Immobilized Gelidium amansii biomass was effective in Pb2+ removal (100%) from aqueous solution at an initial concentration of 200 mg/L for 3 h. In conclusion, it is demonstrated that the red marine alga Gelidium amansii biomass is a promising, efficient, ecofriendly, cost-effective and biodegradable biosorbent for the removal of Pb2+ from the environment and wastewater effluents.

Evaluation of Phthalic Acid Esters in Fish Samples Using Gas Chromatography Tandem Mass Spectrometry with Simplified QuEChERS Technique

Phthalic acid esters (PAEs) have become an important food safety concern due to their lipophilic properties and propensity to accumulate in adipose tissue in edible fish. In this study, a simple, sensitive, and accurate analytical method was successfully established for simultaneous determination of 19 PAEs in fish samples using gas chromatography coupled with tandem mass spectrometry (GC–MS/MS). A simplified Quick, Easy, Cheap, Effective, Rugged, and Safe (QuEChERS) procedure was applied for sample preparation, and the Plackett-Burman factorial design was utilized for optimizing extraction parameters. The calibration curves were linear in the range 0.01–0.5 mg/kg for all of the analyzed PAEs, and the limits of quantification (LOQs) were 0.05–20 μg/kg which are much lower than those in previous reports. The average spiked recoveries ranged from 71.2 to 116.3%, with relative standard deviations (RSDs) of 3.9 to 16.2% (n = 6). Finally, the method was applied to analyze 60 real fish samples taken from Shanghai Municipality, China, and the diisobutyl phthalate (DIBP), dibutyl phthalate (DBP), and bis(2-ethoxyethyl)phthalate (DEHP) were found in almost all fish samples tested in this study. The present study demonstrated that the established method was suitable for market surveillance of 19 PAE residues in fish samples.

Non-thermal microbial inactivation by using supercritical carbon dioxide: Synergic effect of process parameters

In this study, we evaluated the influence of CO2 volume ratio (%) and its synergic effect with the pressure (MPa), temperature (°C) and process time (min) on the inactivation of Lactobacillus casei cells inoculated in apple juice (107 CFU/mL). The effects of process variables on the logarithmic reduction of L. casei cell counts were estimated by a two-level Plackett–Burman factorial design. A Box–Behnken design was subsequently employed to evaluate the interaction between the different factors on the supercritical microbial inactivation. The results showed that the process intensification led to a higher logarithmic reduction. Operating at 15 MPa, 55 °C, 30 min and a 70% CO2 volume ratio, the process was able to reduce L. casei cell counts by more than 6 log cycles. In addition, this work reports the validation of an experimental apparatus assembled by our research group for food processing by employing supercritical carbon dioxide.

Factorial design optimization of micelle enhanced synchronous spectrofluorimetric assay of Omarigliptin: Applied to content uniformity testing and in vitro drug release.

A micelle enhanced spectrofluorimetric method was developed for determination of Omarigliptin (OMG) based on its native fluorescence behavior. The interaction of OMG with surfactants and macromolecules was studied. In aqueous solution, the relative fluorescence intensity (RFI) of OMG was enhanced by 24% in the presence of Tween 80 at pH3.5. The optimal conditions for the micelle enhanced fluorescence were attained by Minitab® program using Plackett-Burman factorial design. Pareto chart, contour plots and surface plots were used to exclude the insignificant variables and optimize the significant factors. The spectrofluorimeter was operated under synchronous mode using ∆λ = 30nm and recording the RFI of the intense narrow band at 267nm for OMG in 0.5% w/v Tween 80 + 0.2M acetate buffer (pH3.5) system using water as diluent. Using synchronous scan mode offered many advantages including considerable reduction of spectral overlap and enhanced linearity of the calibrators. Validation parameters were satisfied over the concentration range 0.1-2μg/ml. The developed method was the first analytical procedure for OMG assay in Marizev® tablets. Moreover, content uniformity testing and in vitro drug release of tablets were performed.