Design Of Response Surface Method Research Articles

Statistical optimization of sulfite pretreatment of corncob residues for high concentration ethanol production

In this study, a central composite design of response surface method was used to optimize sulfite pretreatment of corncob residues, in respect to sulfite charge (5-10%), treatment time (1-2h), liquid/solid (l/s) ratio (6:1-10:1) and temperature (150-180°C) for maximizing glucose production in enzymatic hydrolysis process. The relative optimum condition was obtained as follows: sulfite charge 7.1%, l/s ratio 7.6:1, temperature 156°C for 1.4h, corresponding to 79.3% total glucan converted to glucose+cellobiose. In the subsequent simultaneous saccharification and fermentation (SSF) experiments using 15% glucan substrates pretreated under this kind of conditions, 60.8 g ethanol l(-1) with 72.2% theoretical yield was obtained.

Multi-Objective Optimization of a Wedged-Ring Joint Structure

Finite element method and optimization method are two major ones in engineering analysis. The optimization of a wedged-ring joint structure can be performed by using these two methods unitedly. The response surface design method was employed to determine the combination of geometrical parameters to be designed of the wedged-ring joint structure. The stress of the wedged-ring joint structure which has the different geometrical parameters was numerically simulated and analyzed by using engineering software ANSYS. The optimized geometrical parameters of the wedged-ring structure were obtained by using MATLAB multi-objective optimization method. The results show that the maximum stress and the mass of the optimized wedged-ring structure decrease 13.6% and 12.5%, respectively.

Optimization study on sewage sludge conditioning using Moringa oleifera seeds

Disposal of sewage sludge is a main problem faced by local municipalities in Malaysia. Sludge conditioned with chemical polymer often termed as undesirable use for land application. However, using natural polymer will help to reduce the impact of this problem. In this study, optimization using Moringa oleifera seeds as a natural polymer in sewage sludge conditioning is highlighted. An earlier sludge conditioning using jar test apparatus was conducted using Moringa oleifera seeds in three different forms; dry powder, distilled water extracted and salt extracted (1 N NaCl). Results from the study indicate that Moringa oleifera in distilled water extracted form shows the most optimum reduction in Capillary Suction Time (CST) value. Optimization of three important factors namely mixing speed, mixing duration and Moringa oleifera dosage for distilled water extracted form was done using Design of Experiments (DOE). Optimum values for the selected factors were obtained using Box-Behnken design, Response Surface Design Method (RSM). There was a total of seven set of optimized solutions produced. The best solution generated showed lowest CST and Specifi c Resistance to Filtration (SRF) was obtained at 4.5 s and 1.22 × 1011 m/kg respectively. These values were obtained under the optimum conditions of mixing speed at 100 rpm, mixing duration of 1 min and Moringa oleifera dosage of 4695 mg/L. The desirability index for the optimized solution was 1.000.

Ethanol production from carob extract by using Saccharomyces cerevisiae

Carob has been widely grown in the Mediterranean region for a long time. It has been regarded as only a forest tree and has been neglected for other economical benefits. However, in recent years, this fruit has gained attention for several applications. As petroleum has become depleted, renewable energy production has started to gain attention all over the world; including the production of ethanol from underutilized agricultural products such as carob. In this project, the optimum extraction conditions were determined for the carob fruit by using the response surface design method. The obtained extract was utilized for production of ethanol by using suspended Saccharomyces cerevisiae fermentation. The effect of various fermentation parameters such as pH, media content and inoculum size were evaluated for ethanol fermentation in carob extract. Also, in order to determine economically appropriate nitrogen sources, four different nitrogen sources were evaluated. The optimum extraction condition for carob extract was determined to be 80 °C, 2 h in 1:4 dilution rate (fruit: water ratio) according to the result of response surface analysis (115.3 g/L). When the fermentation with pH at 5.5 was applied, the final ethanol concentration and production rates were 42.6 g/L and 3.37 g/L/h, respectively, which were higher than using an uncontrolled pH. Among inoculum sizes of 1%, 3%, and 5%, 3% was determined as the best inoculum size. The maximum production rate and final ethanol concentration were 3.48 g/L/h and 44.51%, respectively, with an alternative nitrogen source of meat–bone meal. Overall, this study suggested that carob extract can be utilized for production of ethanol in order to meet the demands of renewable energy.

Optimization of osmotic shock process variables for enhancement of the release of periplasmic interferon-α2b from Escherichia coli using response surface method

The osmotic shock process for the release of periplasmic recombinant human interferon-α2b from Escherichia coli was optimized using response surface method (RSM). The process parameters such as pH, buffer concentration and sucrose concentration in hypertonic solution, cell concentration to hypertonic solution, contact time of cells with hypertonic solution, temperature of hypertonic solution, cell concentration to hypotonic solution, contact time of cells with hypotonic solution and temperature of hypotonic solution were initially screened using Plackett Burman design. Further optimization was carried out using central composite design (one of the design in RSM) for sucrose concentration in hypertonic solution as well as cell concentration to hypertonic and hypotonic solutions. The optimal cell concentration was 0.05 g/mL in hypertonic solution and 0.2 g/mL in hypotonic solution. The use of hypertonic solution containing 18% sucrose with a combination of 100 mM Tris and 2.5 mM EDTA buffer (pH 8.0 and 25 °C) and cold water (4 °C) as a hypotonic solution gave the optimum release of interferon-α2b. Increased product concentration in the final solution resulted from the optimized process would reduce the downstream steps during purification. The concept of reuse of hypertonic solution was also demonstrated.

Optimization of H 2SO 4-catalyzed hydrothermal pretreatment of rapeseed straw for bioconversion to ethanol: Focusing on pretreatment at high solids content

A central composite design of response surface method was used to optimize H 2SO 4-catalyzed hydrothermal pretreatment of rapeseed straw, in respect to acid concentration (0.5–2%), treatment time (5–20 min) and solid content (10–20%) at 180 °C. Enzymatic hydrolysis and fermentation were also measured to evaluate the optimal pretreatment conditions for maximizing ethanol production. The results showed that acid concentration and treatment time were more significant than solid content for optimization of xylose release and cellulose recovery. Pretreatment with 1% sulfuric acid and 20% solid content for 10 min at 180 °C was found to be the most optimal condition for pretreatment of rapeseed straw for ethanol production. After pretreatment at the optimal condition and enzymatic hydrolysis, 75.12% total xylan and 63.17% total glucan were converted to xylose and glucose, respectively. Finally, 66.79% of theoretical ethanol yielded after fermentation.

Statistical analysis and validation of process parameters influencing lovastatin production by Monascus purpureus MTCC 369 under solid-state fermentation

Monascus, a fermented rice (red mold rice), was found to reduce total cholesterol and triglyceride in serum due to the presence of lovastatin, a 3-hydroxy-3-methyl glutaryl coenzyme A (HMG-CoA) reductase inhibitor. Optimization and validation of different process parameters such as temperature, fermentation time, inoculum volume, and pH of the solid medium was done using Box-Behnken’s factorial design of response surface method for maximum production of lovastatin by Monascus purpureus MTCC 369. A maximum lovastatin production of 3.422 mg/g was predicted by day 14.43 of fermentation in a rice based solid medium of pH 6 when fermented at a temperature of 29.46°C, an inoculum volume of 5.11 mL, and using response surface plots and the point prediction tool of Design Expert 7.1.3 (Statease Inc., USA) software.

Synthesis and Characterization of Alkyl Methacrylate-based Microgels by Experimental Design Method

In this work, alkyl methacrylate-based microgels were synthesized by an experimental design method, and their sebum absorption characteristics were investigated. The results of fractional factorial experimentation indicated that the cross-linking agent content, solvent content, and stirring speed were the main parameters in the synthesis of the microgels. The suitable synthesis conditions were determined by the response surface design method. Through a study of the monomer and solvent effects, it was confirmed that the microgel shows the highest sebum absorption ratio when t-butyl methacrylate is used as a monomer or when acetone is used as a solvent. The optimal microgel synthesis conditions for cosmetic application were determined, and the resulting microgel had a mean particle size of 4.7 µm and a sebum absorption ratio of 435%.

Solid–liquid extraction of protopine from Fumaria officinalis L.—Experimental study and process optimization

Optimization of the protopine batch extraction from Fumaria officinalis was studied by experimental design. Several parameters were first studied in order to measure their influence on batch extraction thus enabling to choose the most accurate model. A response surface method design that allows investigating the simultaneous variations of the three main parameters (percentage of ethanol in solvent, temperature, solid–liquid weight ratio) was used to evaluate the influence of experimental parameters and their interactions on the extraction yield of protopine. The central composite design (CCD) used for the analysis of treatment combinations showed that a second-order polynomial regression model was in good agreement with the experimental results, with a coefficient of determination of 0.998 and a Fischer test of 1.0. First, this model was validated by variance analysis and experimental checking, then the optimal conditions and the significance of the effects of the parameters were determined. The maximum yield was obtained by using graphical methods and the optimal conditions were obtained when using ethanol 50% (w/w) at a temperature of 79 °C with a 3% solid–liquid (w/w) ratio. Under these optimal conditions, the weight of protopine extracted from 100 g of F. officinalis was about 230 mg.

Statistical Optimization of Bioluminescence of Photobacterium posphoreum KCTC2852.

In this study, media optimization by statistically designed experiments stimulated an increase in the intensity and stability of bioluminescence of Photobacterium phosphoreum KCTC 2852 during continuous cultivation. The Plackett-Burman design method selected two components (NaCl, yeast extract) among nine components of the seawater complete (SC) medium. The response-surface design method calculated the optimum concentration of NaCl (31.1 g/l) and yeast extract (5.1 g/l). In the optimized medium, bioluminescence per cell increased twofold. During continuous cultivation in a stirred tank reactor, bioluminescence decreased rapidly in the SC medium, whereas the optimized medium could maintain bioluminescence for more than 80 h, resulting in an increased bioluminescence. Upon contact with 0.1 ppm Hg2+, a sharp decrease in bioluminescence was observed, which was reproducible in the measuring chamber. This shows the possibility that P. phosphoreum could be cultivated continuously with enhanced bioluminescence stability and that on-line water toxicity could be monitored continuously.