Steepest Ascent Method Research Articles

Influence of co-solvents on fucoxanthin and phlorotannin recovery from brown seaweed using supercritical CO2

Sunflower oil (SFO), soybean oil, canola oil, ethanol, and water were utilized as co-solvents to support supercritical carbon dioxide (SC-CO2) extraction of total carotenoid (TC), fucoxanthin (FX), and phlorotannin (PT) from brown seaweed (Saccharina japonica). A steepest ascent method with various temperatures [45–55°C], pressures [200–300bar], and co-solvent flow rates [0.50–2.00 (% of CO2, w/w)] was used to define the best operative co-solvents to enhance the extraction yields followed by response surface methodology (RSM) to optimize the extraction conditions. The best conditions for the yield of TC and FX were 50.62°C, 300bar, and 2.00% of SFO, while for PT it was 48.98°C, 300bar, and 2.00% of water, respectively. Overall extraction curves were determined for the optimized conditions, and experimental data were used to estimate the kinetic parameters. SFO as co-solvent showed higher fatty acid content, antioxidant activity, and oil stability than the control (SC-CO2 only).

Optimization of astaxanthin pigment bioprocessing by four different yeast species using wheat wastes

Abstract The utilization of wheat wastes in order to produce astaxanthin by pigment producer microorganisms, ATCC 90197 (Yamadazyma guilliermondii), ATCC 24060 (Yarrowia lipolytica), ATCC 24202 (Xanthophyllomyces dendrorhous) and ATCC 24259 (Sporidiobolus salmonicolor) using solid state fermentation technique was carried out pursuant to Box-Behnken design (BBD). Incubation temperature, initial pH and moisture content parameters with three levels were generated for each fermentation process of the microorganisms to optimize the astaxanthin bioprocessing. Maximal astaxanthin with the yield of 109.23 µg AX/g WW was produced by ATCC 24202 at the conditions; 20.0 °C temperature, 5.5 pH and 90.0% moisture content. A second optimization for inoculation rate was followed out by steepest ascent method (SAM). It was revealed that one of the major agro-industrial wastes of the whole world, wheat wastes, might be used to produce value-added astaxanthin pigment biotechnologically.

Integration of Computer Simulation, Design of Experiments and Particle Swarm Optimization to Optimize the Production Line Efficiency

The goal of this paper is to optimize the productivity of manufacturing system by integrating computer simulation, design of experiments (DOE) and particle swarm optimization (PSO) algorithm. Optimizing productivity of colour factory was considered as the case of this study. To evaluate and estimate the effect of main factors, 2n factorial design with higher and upper levels and centre points was considered. After obtaining the significant factors, the local optimum setting of the significant factors was determined using the steepest ascent method and response surface methodology (RSM) approach. Finally, the global optimum productivity was achieved by computer programing of PSO method. Base on the final result, maximum productivity occurs in the point of 87.23 that is relevant to number of labour (B) = 26 and failure time of lifter (C) = 78.04 min. In addition, other two factors A (Service rate of Delpak mixer) and D (Number of permil) should be located at low level to obtain maximum productivity.

Optimization of Process Parameters for Directly Converting Raw Corn Stalk to Biohydrogen by Clostridium sp. FZ11 without Substrate Pretreatment

Statistical analyses had been used to optimize the process parameters of H2 production from untreated raw corn stalk by Clostridium sp. FZ11. Five variables, including the temperature, initial pH, urea, phosphate-buffered saline (PBS), and nutrient solution, had been screened through the Plackett–Burman design. Experimental results indicated that urea, PBS, and nutrient solution were the most important variables, which were further optimized using the steepest ascent method and Box–Behnken design. The maximum H2 yield of 96.2 mL/g from untreated raw corn stalk was recorded under the optimal conditions of 6.21 g/L urea, 0.19 M PBS, and 8.74 mL/L of nutrient solution. Meanwhile, about 45% of cellulose and 53% of hemicellulose were biodegraded by H2 fermentation.

Optimization of Fermentation Medium for Glycyrrhizin Biotransformation to Monoglucuronyl-glycyrrhetinic Acid by Plackett-Burman and Box-Behnken Design

Plackett-Burman (PB) and Box-Behnken (BB) experimental designs were used to optimize fermentation variables for the biotransformation of glycyrrhizin (GL) to monoglucuronyl-glycyrrhetinic acid (MGGA). The PB design was first used to screen the important factors among the medium variables. The steepest ascent method was used to approach the optimum range for each of these factors. The BB design was finally used to analyze the response surfaces of the screened factors for further optimization. The optimized conditions for this system were 0.7 g/L MgSO4·7H2O, 1.19 g/L GL, and cultivation for six days. The biotransformation of GL to MGGA could reach up to 35.72%, which is a good result for this kind of transformation.

Multi‐Cereal Beverage Fermented by Lactobacillus Helveticus and Saccharomyces Cerevisiae

A novel multi-cereal-based fermented beverage with suitable aroma, flavor, and pH fermented by lactic acid bacteria and Saccharomyces cerevisiae was developed. Twenty-seven lactobacilli strains were screened for acid production (pH and titratable acidity) in a mixture of malt, rice, and maize substrates. It was found that Lactobacillus helveticus KLDS1.9204 had the greatest acid production among 27 lactobacilli tested. The fermentation performance of L. helveticus KLDS1.9204 was also assayed and the fermentation parameters were optimized using Plackett-Burman design and steepest ascent method. L. helveticus KLDS1.9204 showed good proteolytic capability, however, the strain could not utilize starch. The optimum substrate consisted of 50% malt (25g/100mL), 25% rice (20g/100mL), and 25% maize (30g/100mL). The inoculum was 5% with a ratio of S. cerevisiae to L. helveticus KLDS1.9204 of 2.5:1. The optimum temperature was 37°C and the time was 22h. Lastly, the quality of the multi-cereal-based fermented beverage was evaluated. This beverage was light yellow, transparent, and it tasted well with a pleasant acid and a unique flavor of cereals. The beverage was rich in free amino acids and organic acids. The pH and titratable acidity of the beverage were 3.5 and 29.86°T, respectively. The soluble solids content of the beverage was 6.5°Brix, and the alcohol content was 0.67%.

Enhanced production of dimethyl phthalate-degrading strain Bacillus sp. QD14 by optimizing fermentation medium

article i nfo Background: Integrated statistical experimental designs were applied to optimize the medium constituents for the production of a dimethyl phthalate (DMP)-degrading strain Bacillus sp. QD14 in shake-flask cultures. A Plackett-Burman design (PBD) was applied to screen for significant factors, followed by the Steepest Ascent Method (SAM) to find the nearest region of maximum response. A Box-Behnken design (BBD) of the Response Surface Methodology (RSM) was conducted to optimize the final levels of the medium components. Results: After the regression equation and response surface contour plots were analyzed, the concentrations of glucose, corn meal and NaCl were found to significantly influence the biomass of DMP-degrading bacteria. A combination of 22.88 g/L of glucose, 11.74 g/L of corn meal, and 10.34 g/L of NaCl was optimum for maximum biomass production of Bacillus sp. QD14. A 57.11% enhancement of the biomass production was gained after optimization in shake-flask cultivation. The biomass production of Bacillus sp. QD14 reached 9.13 ± 0.29 × 10 8 CFU/mL, which was an excellent match for the predicted value, and the mean value of the match degree was as high as 99.30%. Conclusion: In this work, the key factors affected by the fermentation of DMP-degrading strain Bacillus sp. QD14 were optimized by PBD, SAM and BBD (RSM); the yield was increased by 57,11% in the conditions in our study. We propose that the conditions optimized in the study can be applied to the fermentation for commercialization production.

Optimal design of short-armature slotted type multi-segment permanent magnet linear synchronous motor for numerically controlled machine tool

The severe drawback of slotted permanent magnet linear synchronous motor (PMLSM) is the detent force, partic- ularly when accurate positioning and constant low speed is required for numerically controlled machine tool. In this paper, a novel short-armature slotted type multi-segment permanent magnet linear synchronous motor (MSPMLSM) is proposed and constructed to reduce the detent force. It consists of a proper shift of the multiple segments of iron core relative to the PMs. The detent forces of MSPMLSMs with different number of segment are analyzed and simulated by finite element method (FEM). The proposed structure has been proved to be a very effective approach for the reduction of detent force. Then this paper presents the statistical and mathematical optimum design of a 3-segment PMLSM using response surface methodology (RSM) together with FEM to minimize the detent force. Full factorial design and steepest ascent method, one of the iterative search method, is proposed to establish optimal design area for applying RSM. Finally, the global optimal design is predicted and the optimally designed one is manufactured, and the numerical results and measured results are reported to validate the effectiveness of this proposed method.

Optimization of succinic acid production from cane molasses by Actinobacillus succinogenes GXAS137 using response surface methodology (RSM)

A method combining a Plackett-Burman design (PBD), the steepest ascent method (SA), and a Box-Behnken design (BBD) was developed to optimize succinic acid production from cane molasses by Actinobacillus succinogenes GXAS137. The important parameters were (g/L): total sugars of cane molasses (85 g/L), yeast extract (8.84 g/L), and MgCO3 (63.1 g/L). Verification experiments indicated that the maximal succinic acid production reached 57.43±0.86 g/L, which agreed with the predicted value (57.12 g/L). In addition, batch and fed-batch fermentations were carried out in a 1.3 L stirred bioreactor. Compared with a batch fermentation that produced 57.96 g/L of succinic acid at 60 h, a fed-batch fermentation, performed to minimize the inhibition effect of the substrate, produced 64.34 g/L of succinic acid at 60 h. The combined method is powerful for selection of optimized conditions for succinic acid production from cane molasses.

Optimization of medium composition for 3-hydroxycarboxylic acid production by Pseudomonas mendocina-biodegraded polyhydroxybutyrate.

We optimized the culture medium for 3-hydroxycarboxylic acid production by Pseudomonas mendocina DS-04-T-biodegraded polyhydroxybutyrate (PHB) using the Plackett-Burman design, steepest ascent method, and Box-Behnken design. The optimized concentrations of the constituents of the culture medium were as follows: PHB (7.57 g/L), NH4 Cl (5.0 g/L), KH2 PO4 (2.64 g/L), Na2 HPO4 ·12H2 O (12 g/L), MgSO4 ·7H2 O (0.5 g/L), and CaCl2 ·2H2 O (5 mg/L). The yield of 3-hydroxycarboxylic acid obtained using the optimized culture medium was 56.8 ± 1.64%, which was 2.5-fold higher than that obtained when the unoptimized culture medium was used.

A shrinking core model and empirical kinetic approaches in supercritical CO2 extraction of safflower seed oil

Utilization of supercritical CO2 in safflower seed extraction was performed using a semi-batch extractor. Different extraction parameters, such as 40–60MPa pressure, 323–347K temperature, 20–76min time, and 1–3mL/min CO2 flow rate were applied. A two-stage experimental design application was performed in order to maximize the oil yield. First of all, a 32 factorial design was applied to estimate the effect of the main factors and their interactions. The second part of the experimental design was improved and accelerated using the steepest ascent method. Optimum extraction parameters were determined to be 50MPa pressure, 347K temperature and 76min time at a constant CO2 flow rate (3mL/min) according to the 22 design. Under these conditions, the oil yield obtained was 39.42%, comparable with Soxhlet extraction (40%) for 8h. Shrinking core and empirical kinetic models were applied in order to generalize the extraction process. The predicted data was compatible with the experimental data.

Sequential Statistical Optimization of Media Components for the Production of Glucoamylase by Thermophilic Fungus Humicola grisea MTCC 352.

Glucoamylase is an industrially important enzyme which converts soluble starch into glucose. The media components for the production of glucoamylase from thermophilic fungus Humicola grisea MTCC 352 have been optimized. Eight media components, namely, soluble starch, yeast extract, KH2PO4, K2HPO4, NaCl, CaCl2, MgSO4 ·7H2O, and Vogel's trace elements solution, were first screened for their effect on the production of glucoamylase and only four components (soluble starch, yeast extract, K2HPO4, and MgSO4 ·7H2O) were identified as statistically significant using Plackett-Burman design. It was fitted into a first-order model (R 2 = 0.9859). Steepest ascent method was performed to identify the location of optimum. Central composite design was employed to determine the optimum values (soluble starch: 28.41 g/L, yeast extract: 9.61 g/L, K2HPO4: 2.42 g/L, and MgSO4 ·7H2O: 1.91 g/L). The experimental activity of 12.27 U/mL obtained was close to the predicted activity of 12.15. High R 2 value (0.9397), low PRESS value (9.47), and AARD values (2.07%) indicate the accuracy of the proposed model. The glucoamylase production was found to increase from 4.57 U/mL to 12.27 U/mL, a 2.68-fold enhancement, as compared to the unoptimized medium.

Optimization of thermophilic fermentative hydrogen production by the newly isolated Caloranaerobacter azorensis H53214 from deep-sea hydrothermal vent environment

A unique thermophilic fermentative hydrogen-producing strain H53214 was isolated from a deep-sea hydrothermal vent environment, and identified as Caloranaerobacter azorensis based on bacterial 16S rRNA gene analysis. The optimum culture condition for hydrogen production by the bacterium, designated C. azorensis H53214, was investigated by the response surface methodology (RSM). Eight variables including the concentration of NaCl, glucose, yeast, tryptone, FeSO4 and MgSO4, initial pH and incubation temperature were screened based on the Plackett–Burman design. The results showed that initial pH, tryptone and yeast were significant variables, which were further optimized using the steepest ascent method and Box–Behnken design. The optimal culture conditions for hydrogen production were an initial pH of 7.7, 8.3 g L−1 tryptone and 7.9 g L−1 yeast. Under these conditions, the maximum cumulative hydrogen volume, hydrogen yield and maximum H2 production rate were 1.58 L H2 L−1 medium, 1.46 mol H2 mol−1 glucose and 25.7 mmol H2 g−1 cell dry weight (CDW) h−1, respectively. By comparison analysis, strain H53214 was superior to the most thermophilic hydrogen producers because of the high hydrogen production rate. In addition, the isolation of C. azorensis H53214 indicated the deep-sea hydrothermal environment might be a potential source for fermentative hydrogen-producing thermophiles.

An Adaptive Hierarchical Multiscale Algorithm for Estimation of Optimal Well Controls

Summary In determining the optimal well controls by maximizing net present value (NPV) for the remaining life of a reservoir, one typically defines the length of the control steps a priori. Moreover, these control steps are often the same for all wells. We provide a scale-splitting/merging method for adaptively selecting the number and the lengths of control steps as the overall optimization proceeds. We start with a reasonably small number of control steps and find the associated optimal controls by maximizing NPV. Both the adjoint-gradient-based steepest-ascent method and ensemble-based optimization (EnOpt) are considered as optimization algorithms. Because the correlation length used to generate the ad hoc covariance matrix indigenous to EnOpt affects the results, we implement a simple method to reduce the correlation length as the optimization proceeds. This enables EnOpt to generate a good approximation for well-control problems in which the optimal solution is bang-bang. The adaptive approach is applied to two example problems, and the results are compared with those obtained with a predetermined number of control steps.

Minimum Drag Configurations in Hypersonic Flow Via the Method of Steepest Descent

It has been shown that the problem of finding minimum drag configuration in hypersonic flow can be reduced to a problem in optimum control and the method of steepest ascent is a useful tool for finding the solution of this problem.

Optimization of medium composition for exopolysaccharide production by Phellinus nigricans

Using Plackett–Burman design, steepest ascent method, and Box–Behnken design, we carried out sequential statistical optimization of the Phellinus nigricans culture medium for maximizing the production of exopolysaccharides. The concentrations of the constituents of culture medium as optimized by this method were: 51.67g/L glucose, 6.96g/L peptone, 1.0g/L yeast extract, 5mg/L thiamine, 1.0g/L KH2PO4, and 0.5g/L MgSO4. The yield of exopolysaccharides obtained using the optimized culture medium was 1.89±0.13g/L—2.3-fold higher than that obtained when unoptimized culture medium was used. The exopolysaccharide of P. nigricans (PNEP) is comprised by glucose and mannose with the molar ratio 1:2.63. PNEP thus produced scavenged superoxide anion radical, 1,1-diphenyl-2-picrylhydrazyl radical, and hydroxyl radical; showed antioxidant properties; and had reducing power.

Steepest-Ascent Revisited: Unconstrained Missile Trajectory

A Steepest-Ascent numerical procedure for offline trajectory optimization of a surface-to-surface missile attacking a stationary target is presented. A detailed numerical solution, starting from building the mathematical formulation till generating an offline angle of attack control history, is illustrated. A novel approach for guessing a nominal control program is conducted. The formulation entails nonlinear 2-DOF missile flight dynamics with mixed boundary conditions. The technique of changing of variables is adopted to convert the free-final-time optimization problem to a fixed-final-time one. The influences of the optimization algorithm controlling parameters are investigated. A new form of the weighting matrix is proposed. A novel technique of relaxation factors for eliminating the terminal states violation is described. Finally, a comparison between the obtained control history and the one obtained by a nonlinear optimal control package “GPOPS” is presented. The results indicate that the use of Steepest-Ascent method, to a great extent, is comparable in accuracy and iteration time to the pseudospectral optimization package “GPOPS.” This paper, to a great extent, is a detailed procedure for the method of Steepest-Ascent analyzed and verified by the authors from many undetailed sources to disclosure of the main problems faced by user of Steepest-Ascent.

Integrating Steepest Ascent for the Taguchi Experiment: A Simulation Study

Many previous researches conveyed the superiority of Steepest Ascent (SA) method to find the optimal area in Response Surface Methodology (RSM) by shifting the experiment factor level. By using this method, Design of Experiment (DoE) is enabled to shift the factor level gradually in the right track, so that the global optimum can be reached. However, the response variable that is commonly optimized by using RSM cannot fulfill the classical statistics assumption of surface regression model. Taguchi’s orthogonal array, as alternative of RSM, gives loose statistics assumptions in performing the analysis. However, Taguchi’s orthogonal array has not yet been supported to shift the factor level to an optimum direction. Adopting the procedures of RSM in finding the optimal level combination using SA, integrating SA method in the Taguchi experiment is proposed in this paper. This procedure is applied into a simulated response surface. Then, the performance of this procedure is evaluated based on its direction to reach the optimum solution. The simulation data representing the real case is generated for two factors. Then, the proposed procedure is applied. The result of this simulation study shows that the integrated SA method in the Taguchi experiment successfully found the factor level combination that yields optimum response even though it is not as close as possible as the RSM results.

Independent Component Analysis of Functional Magnetic Resonance Imaging (fMRI) Data: A simple Approach

Independent Component Analysis (ICA) separates spatial and temporal components of fMRI data which may consist of activation patterns, cardiac and respiratory tasks and other artifacts. In this study sources of (fMRI) data are separated using ICA based on simple fixed point iteration method and steepest ascent method. Both are the simplest methods used in optimization. However in this study complete matrix W (un-mixing matrix) is updated in each iteration instead of vector based updating of W. This makes the source separation process very fast. Simulated fMRI data is processed using the proposed method and the results are compared with other ICA approaches in terms of speed and accuracy.

Optimization of enzymatic synthesis of L-ascorbyl palmitate by solvent engineering and statistical experimental designs

Statistical experimental designs combined with solvent engineering for optimization of enzymatic synthesis of L-ascorbyl palmitate were developed. First, the composition of the solvent for co-dissolving polar and apolar substrates was determined. The co-solvent mixture of tert-pentanol: DMSO at a ratio of 9:1 (v/v) and the optimal biocatalyst were obtained. Then, the Plackett-Burman design was implemented to screen the variables that significantly influence the conversion. The method of steepest ascent was used to approach the proximity of optimum. After determining the Plackett-Burman and steepest ascent designs, the optimum values were determined by central composite design under response surface methodology. The statistical analysis showed that the optimum reaction conditions (temperature 50°C, enzyme concentration 5.8 g/L, and substrate molar ratio 11:1, stirring rate 160 rpm, amount of molecular sieve 50 g/L, time 18 h) led to the maximum conversion (66.44%) and production concentration (20.63 g/L). A very satisfactory conversion (64.74%) and production concentration (20.13 g/L) could be achieved in short time (6 h).