Showing 110 results for روش سطح پاسخ
Volume 4, Issue 3 (12-2020)
Abstract
Research subject: Superabsorbents are hydrophilic hydrogels that can accommodate large amounts of water in their three-dimensional structures and have wide applications in various sciences such as pharmaceuticals, medicine, and agriculture. These materials are hydrophilic polymers that are physically or chemically cross-linked. Conversion and swelling ratio of synthesized hydrogels are two counter effects. Therefore, determining the appropriate conditions for polymerization to achieve optimal properties and swelling rate of hydrogels is a challenge for researchers.
Research approach: In this study, optimizing the synthesis conditions of semi-interpenetrating poly (acrylic acid)/xanthan hydrogels, the response surface methodology (RSM) was used by Box-Behnken design (BBD). The variables of this method were the molar ratio of the cross-linking agent (X1), the weight percentage of xanthan gum (X2) as the reaction medium, and the amount of initiator (X3), each of which was considered at three levels. The evaluated responses in RSM were the rate of polymerization conversion (Y1) and the rate of swelling (Y2) of the hydrogels in the water.
Main results: Based on the 17 experiments proposed by RSM (BBD), the cross-linker, xanthan gum, and initiator were combined and radical polymerization was performed into silicone molds at 65 ° C. The results of ANOVA analysis showed that the data error of this study was small and the coefficient of determination (R2) of both proposed models for the responses Y1 and Y2 was higher than 0.9. The 46 experiments proposed for the optimal point by RSM (BBD) with the desirability of more than 50% indicate the synthesis of hydrogels that have both a good conversion rate and an optimal amount of swelling. For example, by 13% of cross-linking agent, 0.043 g of initiator and 1% wt. the solution of xanthan, hydrogels with a 95% conversion rate, and 102% water uptake were prepared. These hydrogels can be used in a variety of fields, including the treatment of colored wastes in factories, agriculture, pharmaceutical systems, medical attractions, and more.
Volume 5, Issue 1 (6-2016)
Abstract
The response surface methodology was employed to optimize the effects of pH, temperature (˚C), time (min) and the ratio of enzyme to substrate (% of substrate) on the hydrolysis process of cuttlefish muscle by alcalase. Central composite rotatable design with 5 levels and 4 factors and α=2 was used for the optimization of the process to gain the highest degree of hydrolysis. pH, temperature, time, enzyme concentration, interaction of temperature-enzyme concentration, square of pH, temperature, time and enzyme concentration had significant effects on the process. The R2 = 0.95, lack of fit < 0.05 and adeq-Precision of 14.16 for the model showed that the model could explain the variability within the range of values. The optimum condition for 42.0117 % of degree of hydrolysis was determined by Design Expert as pH 8.19, temperature 50.23, time 129.62 and enzyme2.15%.
Volume 5, Issue 2 (8-2014)
Abstract
Lovastatin is a potent agent for lowering cholesterol of blood. Since one of the main reasons of mortality in developing countries is cardiovascular disease, which is caused by precipitation of fatty acid (especially cholesterol) in blood vessels; therefore diets containing lovastatin may prevent this type of disease. In this study, Lovastatin, monacolin K or competitive inhibitor of the HMG-CoA reductase (operative enzyme for cholesterol synthesis) was produced by submerged fermentation using Monascus purpureus PTCC5303. Seven chemical and nutritional parameters including maltose, peptone, MgSO4.7H2O, MnSO4.H2O, KH2PO4, thiamin and pH screened using Plackett Burman experimental design for monacolin production. Among different parameters, maltose and MgSO4.7H2O showed significant effect on biomass and monacolin production. The concentration of these agents were optimized using response surface methodology for lovastatin production in the shaker flask. The optimized medium contained 26 g/L maltose, 5 g/L peptone, 0.1 g/L MgSO4.7H2O, MnSO4.H2O 0.5 g/L, 4 g/L KH2PO4, Vitamin B1 0.1 g/L and pH 7. After 10 days of fermentation in the shaker flask with 130 rpm agitation and 30 ºC, we achieved maximum lovastatin production which was 63 mg/l.
Volume 5, Issue 4 (4-2021)
Abstract
Research subject: Nowadays, due to the prevalence of coronavirus and the increasing use of disinfectant solutions and gels, the use of glycerin has also increased dramatically. But the suggested processes in this field need to be optimized in terms of production and energy consumption.
Research approach: In this paper, the transesterification method has studied and simulated, during which vegetable oil is converted into biofuel, and glycerin is also produced as a by-product of this process. For this purpose, process simulation of a conventional unit with 5.5 m3/min feed has been done in Hysys. Also, due to the importance of equipping the transesterification reactor, by importing the necessary process information, this equipment has been simulated in COMSOL MultiPhysics and the effective parameters have been studied in order to optimize the of product conversion. After validation of model, to better understand the factors affecting the performance of the transesterification reactor, the effect of selected parameters first examined by one-variable at the time design of experiment approach.
Main result: Finally, it has been shown that the feed temperature and the flowrate both have significance impact on quantity and quality of product and while providing a model for calculating the amount of glycerol produced per unit of energy consumed, the effective parameters are optimized by the response surface method. In optimal conditions of the ratio of product production to energy consumption, the temperature value was 470.7 K and the feed flow rate was 0.586 m3/s. According to the gained results, it can be obtained by adjusting the flow rate in the optimal amount, using a preheater in the production processes of biofuels and glycerin can have a significant effect on the amount of products produced so that the optimal temperature for the output of this preheater is at least 470.7 K should be considered. In the current research an optimization scheme has been suggested which can be used for different Biodiesel-Glycerol production units with varies range of flowrate.
Volume 8, Issue 1 (3-2024)
Abstract
Research subject: This study aims to improve the biocompatibility, bioactivity, and mechanical properties of gelatin-based composite scaffolds by coating them with polyethylene glycol (PEG) doped with bioactive glasses (BGs) containing zinc and magnesium.
Research approach: A response surface methodology (RSM) was used to model and evaluate the effects of two independent variables: the PEG/Gel weight ratio (X1) and the BG weight percentage (X2). The responses investigated included ultimate strength, Young's modulus, elongation at break, swelling percentage, erosion percentage, and moisture absorption percentage.
Main results: Optimal conditions were determined to obtain scaffolds with suitable mechanical strength, biocompatibility and degradability. Analysis of variance (ANOVA) was used to obtain the best model describing the influence of each independent variable on the responses. The optimal scaffold formulation was selected based on software-defined parameters. The FTIR spectrum was used to analyze the functional groups present on the surface of the samples. The FTIR spectrum of the synthesized BGs showed a broad vibrational band in the range of 900 to 1100 cm-1, which is attributed to the asymmetric Si-O-Si stretching band. The FTIR spectrum of the PEG/Gel/BG composite confirmed the presence of BG in the scaffolds and the interaction between the polymer matrix and BG. Increasing the amount of BG relative to the polymer scaffold led to a decrease in pore size and consequently, a decrease in the scaffold's swelling percentage. The effect of varying the BG weight percentage on tensile strength was greater than that of the PEG/Gel weight ratio. The tensile strength increased significantly due to the good interaction between the polymer scaffold and BG, as well as the uniform dispersion of BG within the polymer matrix. SEM images indicated that cells penetrated well into the scaffolds and formed a suitable three-dimensional cellular network. Cytotoxicity, cell attachment and proliferation, and osteogenic differentiation were evaluated using the MTT test and by culturing MG-63 cells on the scaffold. Cell viability showed no significant difference between the tested and control samples.
Volume 8, Issue 2 (10-2017)
Abstract
Production of recombinant proteins in Escherichia coli has been very common in recent decades. Many studies and experiments have been done in order to optimize the production and expression of recombinant proteins in E.coli. One strategy is using high cell density to increase recombinant protein production such as β-NGF in the cell. Therefore, in this study for the first time bacterial cell culture in high cell density was done using glycerol and yeast extract as carbon and nitrogen sources and MgCl2 as a growth effective factor. Also the effects of overnight culture conditions on bacterial growth were evaluated. Meanwhile culture conditions were optimized using response surface methodology (RSM) and the optimum conditions were as follows: 18/23 g/lit glycerol, 14.44 g/lit yeast extract and 10mM MgCl2. Also the obtained results indicated that the 14 hours incubation at 37 °C and 180 rpm were optimum conditions for the overnight culture. Our results showed that the rate of cell growth and recombinant β-NGF production in optimized condition is significantly higher than in basic medium.
Volume 9, Issue 37 (12-2012)
Abstract
Emulsion coatings were formulated and films were developed using tragacanth gum as the basic structural component. Preliminary experiments were carried out to determine the proper concentration of tragacanth gum, lipid and plasticizers in the film. The effects of different concentrations of tragacanth gum (0.65, 1, 1.5, 2, 2.35 g /g distilled water), canola oil (23, 30, 40, 50, 58 g/g tragacanth dry wt basis) and glycerol (33, 40, 50, 60, 67 g/g tragacanth dry wt basis) on water vapor permeability (WVP), mechanical properties and opacity (OP) of the films were evaluated using the response surface methodology. WVP was observed in the range of (2.05-36) x 10-11 and increased by tragacanth and glycerol concentration and was decreased by oil concentration. Tensile strength and elongation at break ranged between 0.67-7.15 Mpa and 1.99 – 7.8%; respectively. Increasing the amount of tragacanth gum and decreasing the glycerol and oil concentration increased tensile strength (TS) while elongation at break (EB) increased by increasing both tragacanth and glycerol concentration and decreased by increasing oil concentration. Oil was the most influential factor that affected opacity, which increased with increasing oil concentration. Models developed for WVP, EB, TS and OP had high coefficient of multiple determination (R2) values (0.983, 0.952, 0.824, 0.94) respectively.
Volume 10, Issue 38 (1-2013)
Abstract
Protein rich legumes are suitable for the production of edible films and coatings. In this research, pea protein isolate was obtained from defatted pea flour by alkaline extraction and acid precipitation. Then edible films were prepared from pea protein isolate. The effects of protein and glycerol concentrations on water vapor transmission rate (WVTR), mechanical properties, thickness, opacity and total color difference (ΔE) of the films were evaluated, using response surface methodology (RSM). The results showed that WVTR, elongation, ΔE, thickness and opacity were increased, while tensile strength decreased by glycerol concentration. Increasing the concentration of protein increased tensile strength, opacity and ΔE, while decreased WVTR and elongation of the films. The model developed by RSM for the physical and mechanical properties of the films had high coefficient of multiple determination (R2 >0.87) and significant F values.
Volume 10, Issue 40 (7-2013)
Abstract
Edible films and coatings are developed to improve quality and to extend shelf-life of food products. In this study, soy protein isolate was obtained from defatted soy flour by alkaline extraction and acid precipitation. Then edible films were prepared from soy protein isolate. The effects of protein concentrations and two plasticizers of glycerol and sorbitol on some physical and mechanical properties of the films were evaluated, using response surface methodology (RSM). The results showed that tensile strength, opacity, thickness and water vapor transmission rate (WVTR) were increased, while elongation of the films decreased by protein concentration. Increasing the concentration of glycerol and sorbitol increased WVTR, elongation, total color difference (ΔE), thickness and opacity, while declined tensile strength of the films. The model developed by RSM for the physical and mechanical properties of the films had high coefficient of multiple determination (R2 >0.87) and significant F values. The models suggested that the concentration of soy protein and the type and concentrations of the plasticizers are the most influential factors with significant effects on the properties of soy protein isolate films.
Volume 11, Issue 42 (2-2014)
Abstract
One of the most important researches areas in food industry is setting parameters in an optimal level to improve process functions. A literature research in food science and technology databases reveals that in recent years many optimization methods have been developed to improve food processing. However, most of these methods have only dealt with a single objective problem. In many situations the quality of a manufactured product is often evaluated by several quality characteristics and multiple objectives must be optimized simultaneously. In this article we propose a method that integrates design of experiments, response surface technique and Signal-to-Noise (SN) ratio concept for optimization of a kind of yoghurt, called Whey Less, with three objectives: TS, Acidity and cost per unit. The proposed method considers both the mean and the variation of quality losses associated with several objectives, and ensures a small variation in quality losses among the objective functions, along with a small overall average loss. Moreover, this method can be used for both kinds of decision variables (discrete and continuous) and its implementation is easy.
Volume 11, Issue 43 (4-2014)
Abstract
From 1999 and 2000, DAG oil production has been started in Japan and USA. It must be mentioned that DAG oil has been considered as useful product for human health and it is known as functional and nutraceutical cooking oil. The objective of this study was to evaluate reaction parameters in DAG production from safflower oil and to optimize the process to obtain maximum yield of DAG. After safflower oil extraction, enzymatic glycerolysis was used to produce DAG oil. The treatments were determined using Design-expert software and after modeling, the process optimization was done. Finally, some physicochemical properties of DAG oil were investigated. After modeling, it was observed that the enzyme load had linear effect while the reaction temperature and glycerol content showed the quadratic effect on DAG yield. Also it was obtained that there was significant interaction effect between enzyme load/time, enzyme load/ glycerol and time/glycerol. Results showed that there was no significant difference between DAG and safflower oils in terms of specific gravity and iodine value but refractive index, color and peroxide value were different. Maximum production of DAG (48.454 %) obtained at reaction temperature of 46.9 ºC, reaction time of 4 h, enzyme load of 0.75 % (weight of oil), and molar ratio of glycerol to oil 2:1 which was increased to 53.84 % after product purification.
Volume 11, Issue 44 (2-2014)
Abstract
In this research, the culture condition improvement on phytase productionby Aspergillus ficuum PTCC 5288 was investigated using submergedfermentation method in 250 ml shake flask. Four factors which influencing phytase production, including carbon source (glucose) in five level (2, 3.5, 5, 6.5 and 8 g/100 mL), nitrogen source (ammonium sulphate) five levels (1, 2, 3, 4 and 5 g/100 mL), phosphor source (wheat bran) five levels (1, 2, 3, 4 and 5 g/100 mL),and fermentation time five levels (48, 120, 192, 264 and 336 hour) were studied. The optimum levels of these significant factors were determined via response surface methodological approach as: 5.23g/100 mL glucose, 1.6 g/100 mL ammonium sulphate, 3.28 g/100 mL glucose wheat branand198.30 hours.The maximum predicted amount of phytase was 39.61 U/mL and the produced amount of phytase under these conditions was 40.21 U/mL, which indicates the efficacy of the model for prediction of phytase production content under different conditions of the medium.
Volume 12, Issue 3 (9-2021)
Abstract
Hyaluronic acid (HA) is a natural and linear polymer that finds a wide-range of applications in medicine, cosmetics, and nutraceuticals because of excellent viscoelasticity, high moisture retention capacity, high biocompatibility and non-toxicity. HA has been recently produced in industrial scale by Streptococcal species. Streptococci are nutritionally fastidious lactic acid bacteria and cannot synthesize some amino acids. Therefore, it is necessary to study and select some commercial culture media for their growth. In this study, HA production and hyaluronidase activity of S. zooepidemicus ATCC 43079 in three culture media were investigated. Regarding the detrimental effect of this enzyme on HA amount, 6-O-Palmitoyl-L-ascorbic acid as hyaluronidase inhibitor was added to culture medium during fermentation. The effect of three variables consisted of glucose concentration, yeast extract concentration and medium pH each at 3 levels were considered and (response surface methodology (RSM) was used for statistical design of experiments to study the HA production by this strain. The results showed that maximum HA production was obtained when glucose concentration, yeast extract concentration and pH were 21.2 g L-1, 43.6 g L-1 and 6.6, respectively. Under optimum conditions, HA was produced as 370±15 mg L-1 which was ~150% more than of HA concentration in basal medium (150±10 mg L-1) and productivity reached 56.74 g L-1 h-1 that was increased 2 fold compared to central point.
Volume 13, Issue 0 (11-2015)
Abstract
Phytases (myo-inositol 1,2,3,4,5,6 hexakis phospho-hydrolase), found in plants, animal tissues and microorganisms, are a group of phosphatases capable of hydrolyzing phytic acid, the most abundant inositiol phosphate in nature, to myo-inositol and inorganic phosphates. In this study, 68 microbial isolates from different sources were screened using submerged fermentation for the best phytase production. The results showed that isolate K46b had the highest phytase production (1.952 U/mL) among other isolates. Subsequently, the catalytic activity of phytase enzyme of isolate K46b at different conditions of temperature, pH and sodium phytate concentration was optimized using response surface methodology (RSM). Under optimum conditions i.e. 56.5 ºC, pH 7.30 and 2.05 mM sodium phytate, the phytase activity increased to 4.627 U/mL which compared to the screening step, it showed a 137% increase. Moreover, the phytase showed 60-73% of its optimum activity in wide ranges of temperature (47-68 ºC), pH (6.3-8.0) and sodium phytate (1.04-2.50 mM). It can be concluded that isolate K46b phytase has potential applications in dephytinization of food ingredients such as cereals and meals in in food and animal feed industries, aquaculture and combating phosphorous pollution in the environment.
Volume 13, Issue 1 (3-2022)
Abstract
Mutation in microbial strains to increase coenzyme Q10 production is one of the successful strategies for strain development. Therefore, in this study, the production of coenzyme Q10 by Gluconobacter oxydans H621 was investigated through chemical mutation with nitrosoguanidine using the response surface methodology. Nitrosoguanidine was used to induce mutations at different concentrations (2.79 - 4.21 mg/mL) and treatment times (11.89 – 33.12 minutes), which was designed by a central composite design. The detection of mutant strains was investigated through their ability to grow in medium containing 160 μg/mL of menadione. The mutant strains were then examined for coenzyme Q10 and dry cell weight production. The results showed that no mutant strains were obtained at a concentration of 4 mg/ml and above. The highest number of mutant colonies was obtained at a concentration of 2.79 mg/mL of nitrosoguanidine and treatment time of 22.5 minutes. It was also found that the concentration of nitrosoguanidine was effective on mutagenesis but the treatment time had a little effect. The mutant strain that was able to produce the highest amount of coenzyme Q10 produced 5.2 mg/L, which was twice as much as the parent strain. According to the results of this study, it is concluded that by inducing mutation using nitrosoguanidine, mutant strains can be generated in Gluconobacter oxydans H621 that are able to produce more coenzyme Q10 than the parent strain.
Volume 13, Issue 50 (5-2016)
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Volume 13, Issue 50 (5-2016)
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Volume 13, Issue 50 (5-2016)
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Volume 13, Issue 50 (5-2016)
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Volume 13, Issue 55 (9-2015)
Abstract
With emerging of infectious diseases and spread of antibiotic resistant strains, use of antimicrobial compounds with plant origin seems necessary. In this study, ethanolic extract of Cordia myxa fruit was used to evaluate antimicrobial effects against microorganisms including Bacillus cereus, Staphylococcus aureus, Escherichia coli, Salmonella typhi, Aspergillus niger and Candida albicans. Ultrasound-assisted extraction was performed to investigate three independent variables: time (5- 40 min), temperature (20- 50°C) and sonic power (20- 100%). Response surface methodology was also employed to optimize multiple variables to predict the best process conditions. Antimicrobial activity was done by methods including disk diffusion agar, pour-plate, minimum inhibition concentration and minimum bactericide (fungicide) concentration. The results showed that the highest amount of extraction rate of ethanolic extract which was equal to 8.5%, was obtained in extraction time of 39.8 min, temperature of 42.2°C and sonic power of 94.4%.In all above-mentioned methods, inhibitory effect of optimum ethanolic extract was more significant againstBacillus cereus, Staphylococcus aureus and Candida albicansthan other strains (p≤0.05).