Path Of Steepest Ascent Research Articles

Optimization of Biosorption of Reactive Blue 222 by Dead Biomass of Rhizopus arrhizus NCIM997 Using Response Surface Methodology

The present investigation deals with utilization of dead fungal biomass of Rhizopus arrhizus NCIM 997 as a low-cost biosorbent and optimization of conditions for the removal of Reactive Blue 222 dye from aqueous solution using sequential statistically designed experiments. Plackett - Burman design with six independent variables (pH, concentration of dye, concentration of biosorbent, temperature, speed of agitation and contact time), was used initially to identify the most significant factors influencing biosorption. Path of Steepest Ascent was then used to move towards the vicinity of optimum operating conditions. Central Composite Design at the specified combinations of four significant factors identified by Plackett–Burman Design (pH, concentration of dye, concentration of biosorbent, contact time) and response surface analysis were then adopted to investigate mutual interactions between these variables and to identify their optimal values. The maximum sorption (72.89 mg g-1) was obtained under following conditions: pH 1.5, initial concentration of dye 88 mgL-1, concentration of biosorbent 1.2 gL-1 and contact time 111 min. Validation experiments showed excellent correlation between predicted and experimental values. The fitted quadratic model was used to arrive at the best operating conditions to achieve a maximum response. The sequential optimization was successfully used to increase biosorption by 12.82%.

Characterization and Process Optimization in the Extraction of Gold

Refractory gold ore understudied showed traces amount of gold from X-ray fluorescence analysis. Phases identified are quartz, muscovite and calcite. Statistical approach using response surface methodology - central composite design were performed at varying concentration of NaCN, Pb (NO3)2 and H2O2. Cyanidation experiments were conducted at room temperature at pH 11. Using the response surface methodology followed by path of steepest ascent, gold cyanidation was found to be at 467.3 ppm NaCN, 94.96 ppm Pb (NO3)2 and 0.01M H2O2, at the vicinity towards the optimum condition where 88.97% Au extracted from the ore, equivalent to 1.7231 g/t Au.

Actinobacillus succinogenes의 혐기성배양에 의해 생합성 되는 숙신산의 생산성 향상을 위한 통계적 생산배지 최적화

Statistical medium optimization has been carried out for the production of succinic acid in anaerobic fermentations of Actinobacillus succinogenes. Succinic acid utilized as a precursor of many industrially important chemicals is a fourcarbon dicarboxylic acid, biosynthesized as one of the fermentation products of anaerobic metabolism by A. succinogenes. Through OFAT (one factor at a time) experiments, corn steep liquor (CSL), a very cheap agricultural byproduct, was found to have significant effects on enhanced production of succinic acid, when supplemented along with yeast extract. Hence, using these factors including glucose as a carbon/energy source, interactive effects were investigated through <TEX>$2^n$</TEX> full factorial design (FFD) experiments, showing that the concentration of each component (i.e., glucose, yeast extract and CSL) should be higher. Further statistical experiments were conducted along the steepest ascent path, followed by response surface method (RSM) in order to find out optimal concentrations of each constituent. Consequently, optimized concentrations of glucose, yeast extract and CSL were observed to be 180 g/L, 15.08 g/L and 20.75 g/L respectively (10 g/L of <TEX>$NaHCO_3$</TEX> and 100 g/L of <TEX>$MgCO_3$</TEX> to be supplemented as bicarbonate suppliers), with the estimated production level of succinic acid to be 92.9 g/L (about 3.5 fold higher productivity as compared to the initial medium). Notably, the RSM-estimated production level was almost similar to the amount of succinic acid (92.9 g/L vs. 89.1 g/L) produced through the actual fermentation process performed using the statistically optimized production medium.

Enhancing the Production of a Novel Exopolysaccharide by &lt;i&gt;Bacillus mucilaginosus&lt;/i&gt; CGMCC5766 Using Statistical Experiment Design

Purpose: To improve the production of a novel exopolysaccharide (EPS) by Bacillus mucilaginosus CGMCC5766.Methods: The culture medium for production of EPS was optimized using statistical experiment design. Sucrose, CaCO3 and K2HPO4 were found to be the key factors based on the results obtained from Plackett–Burman experimental design. The optimal concentration range of the three factors was examined by the steepest ascent path, and then the optimum concentration was further investigated through response surface methodology. Validation experiments were also carried out to establish the adequacy and accuracy of the model obtained.Results: Under optimal conditions (sucrose 61.31 g/l, CaCO3 5.06 g/l and K2HPO4 0.17 g/l), EPS concentration achieved 22.04 g/l, which was about 1.6-fold increase compared with that using the original medium. EPS concentration in 5-l fermenter reached 23.46 ± 0.76 g/l.Conclusion: The optimization medium is considered fundamental and useful for the development of B. mucilaginosus CGMCC5766 cultivation process for efficient production of EPS on a large scale.Keywords: Bacillus mucilaginosus CGMCC5766, Exopolysaccharide, Medium, Optimization, Statistical experiment design

Statistical Screening of Factors Affecting Production of Fermentable Sugars from Sugarcane Bagasse under Solid-state Conditions

A Plackett-Burman design (PBD) combined with a steepest ascent approach is a powerful technique to screen the important operating parameters for the production of reducing sugars from sugarcane bagasse (SB). In this study, the most significant parameters (p< 0.05), as identified by PBD, were as follows: pretreatment duration, pH of pretreatment process, loading of enzyme cellulase, SB loading, and moisture content of SB. Analysis of variance (ANOVA) results showed that the model of reducing sugar productivity was able to provide a high correlation between the response and its parameters. Thus, the path of steepest ascent (PSA) method was used to assess the optimal region of variables for improved reducing sugar productivity from SB. The PSA analysis revealed that by treating 7.25 g of SB (with 84% moisture content) for 82.0 minutes at a pH of 8.8, followed by the addition of 34.0% v/w of cellulase, a reducing sugar productivity of 0.03 g/L could be achieved per hour during the enzymatic saccharification process.

Bio-Hydrogen Production from Pineapple Waste Extract by Anaerobic Mixed Cultures

A statistical experimental design was employed to optimize factors that affect the production of hydrogen from the glucose contained in pineapple waste extract by anaerobic mixed cultures. Results from Plackett-Burman design indicated that substrate concentration, initial pH and FeSO4 concentration had a statistically significant (p ≤ 0.05) influence on the hydrogen production potential (Ps) and the specific hydrogen production rate (SHPR). The path of steepest ascent was undertaken to approach the optimal region of these three significant factors which was then optimized using response surface methodology (RSM) with central composite design (CCD). The presence of a substrate concentration of 25.76 g-total sugar/L, initial pH of 5.56, and FeSO4 concentration of 0.81 g/L gave a maximum predicted Ps of 5489 mL H2/L, hydrogen yield of 1.83 mol H2/mol glucose, and SHPR of 77.31 mL H2/g-volatile suspended solid (VSS) h. A verification experiment indicated highly reproducible results with the observed Ps and SHPR being only 1.13% and 1.14% different from the predicted values.

Application of an Integrated Statistical Design for Optimization of Culture Condition for Ammonium Removal by Nitrosomonas europaea

Statistical methodology was applied to the optimization of the ammonium oxidation by Nitrosomonas europaea for biomass concentration (CB), nitrite yield (YN) and ammonium removal (RA). Initial screening by Plackett-Burman design was performed to select major variables out of nineteen factors, among which NH4Cl concentration (CN), trace element solution (TES), agitation speed (AS), and fermentation time (T) were found to have significant effects. Path of steepest ascent and response surface methodology was applied to optimize the levels of the selected factors. Finally, multi-objective optimization was used to obtain optimal condition by compromise of the three desirable objectives through a combination of weighted coefficient method coupled with entropy measurement methodology. These models enabled us to identify the optimum operation conditions (CN = 84.1 mM; TES = 0.74 ml; AS = 100 rpm and T = 78 h), under which CB = 3.386×108 cells/ml; YN = 1.98 mg/mg and RA = 97.76% were simultaneously obtained. The optimized conditions were shown to be feasible through verification tests.

Use of response surface methods and path of steepest ascent to optimize ligand-binding assay sensitivity

Response surface methods (RSM) combined with a steepest ascent approach is a powerful technique to optimize assay performance. In this case, a ligand-binding assay (LBA) to quantitate a peptide biotherapeutic was optimized for improved sensitivity using this technique. Conditions were elucidated to enable pg/mL quantitation of the peptide in human plasma using steepest ascent to efficiently optimize assay factors. Instead of relying solely on assay development experience and intuition to improve assay sensitivity, this systematic approach takes advantage of a predictive mathematical model generated through response surface methods that defines a specific path towards greater predicted assay sensitivity. The actual response observed along the steepest ascent path was in good agreement with the model for several steps, until reagent concentrations moved beyond the physical limits of the system, and model breakdown occurred. RSM combined with steepest ascent method proved a useful tool for sensitivity optimization in three ways: (1) The required LBA sensitivity performance (approximately 200pg/mL), measured as a signal-to-noise ratio (SNR) at the targeted lower limit of quantitation (LLOQ), was efficiently achieved in only two optimization experiments; (2) Steepest ascent confirmed that the desired sensitivity was found within the initial RSM design space, and no further gain in sensitivity was found venturing beyond this design space along the steepest ascent path; (3) The desired assay sensitivity was maintained over a reasonable range of reagent concentrations along the steepest ascent path, indicating assay robustness for this parameter.

Optimization of Fermentation Medium for Producing α-Hydroxyphenylacetic Acid by Using Plackett-Burman Design and Response Surface Methodology

Plackett-Burman design and response surface methodology were applied in order to optimize the fermentation medium of (R)-α-hydroxyphenylacetic acid ((R)-HPA) producing Bacillus sp. HZG-19. The factors playing important roles in the production of (R)-HPA were selected based on Plackett-Burman design. The path of steepest ascent was undertaken to optimize said fermentation medium. Finally, the optimal levels of the factors with the greatest change in regard to product yield were further optimized using Box-Behnken and response surface analysis. The optimal conditions were found to be as follows: casein peptone 30.49 (g × L-1), glycerol 14.09 (g × L-1), KH2PO4 0.1345 (g × L-1), K2HPO4 0.01 (g × L-1), CaCl2 0.1 (g × L-1), MnSO4 0.01 (g × L-1). Under the optimal conditions described above, the yield of (R)-HPA reached 63.30%, which indicated an increase of 14.9%, as compared to the yield obtained before optimization.

Enhanced Mycelial Biomass Production of the Hairy Bracket Mushroom, Trametes hirsuta (Higher Basidiomycetes), by Optimizing Medium Component with Plackett-Burman Design and Response Surface Methodology

Statistical analyses based on experimental designs were applied to optimize the medium components for mycelial biomass production by Trametes hirsuta in shake flask cultivation. First, the effects of different carbon resources (glucose, sucrose, lactose, maltose, fructose, soluble starch and potato), nitrogen resources (yeast extract, peptone, (NH4)2SO4, NH4NO3, NH4Cl, peanut powder, soybean powder) and mineral elements (CaCl2, ZnSO4·7H2O, FeSO4·7H2O, MnSO4·H2O, CuSO4·7H2O) on mycelial biomass production were investigated using a univariate design. Second, a Plackett-Burman design was applied to identify the significant variables that principally influenced the mycelial biomass production, and the path of steepest ascent was pursued to approach the regions of optimal value of the significant variables. Subsequently, these significant variables were optimized using the Box-Behnken design of response surface methodology. Ultimately, the optimized medium conditions were composed of sucrose 25.65 g·L-1, MgSO4·7H2O 1.24 g·L-1, and FeSO4·7H2O 3.36 g·L-1, and the yield of mycelial biomass reached 15.45 g·L-1, which represents an approximately 1.6-fold increase above the initial yield.

Optimizing Bismuth-Modified Graphene-Carbon Nanotube Composite-Coated Screen Printed Electrode for Lead-Ion Sensing through the Experimental Design Strategy

A three-dimensional graphene-carbon nanotube (G-CNT) composite-coated screen printed electrode (SPE) is developed as the substrate for bismuth-modified electrodes to measure trace lead ions in this work. This G-CNT/SPE is modified with Nafion and then deposited with Bi nanoparticles, denoted as Bi/Nafion/G-CNT/SPE. Due to smooth electron pathways and effective exposure of Bi nanoparticles on G-CNT and the negative charge of Nafion, the Pb2+-sensing ability of Bi/Nafion/G-CNT/SPE is over 50 times of that of a Bi-deposited SPE electrode, which can be further optimized by the experimental design strategy combining the fractional factorial design (FFD) and the steepest ascent path (SAP) studies. In the FFD study, the concentration of Nafion and pH of the stripping buffer solution are identified to be the key factors affecting the stripping current of lead pre-deposited onto Bi/Nafion/G-CNT/SPE. From the SAP study, a simple but reliable model for increasing the lead-ion sensitivity of Bi/Nafion/G-CNT/SPE has been constructed. The highest stripping current response of lead-ion sensing on Bi/Nafion/G-CNT/SPE can be obtained when 0.3% Nafion and the stripping buffer solution with pH = 4.75 are employed.

Cryogenic Freezing Process Optimization Based On Desirability Function on the Path of Steepest Ascent

Cryogenic Freezing Process Optimization Based On Desirability Function on the Path of Steepest Ascent

REGRESSION-BASED OPTIMIZATION OF THE PARTIAL OXIDATION OF METHANE ON NIMGO/Α-ALUMINA MONOLITH CATALYST IN A REVERSE-FLOW REACTOR

This study describes the use of statistical optimization techniques on a laboratory scale reverse flow reactor for the catalytic partial oxidation of methane on Ni-MgO/α-alumina monolith catalyst. The effects of initial temperature (Tini), switching time (τ), total flow rate (F), mole fraction of methane (M), and catalyst length on hydrogen yield and methane conversion are investigated using systematic experimental design. In the first experimental phase, the steepest ascent path was established by ridge analysis to determine the stationary point. The optimum operating conditions were determined in the second experimental phase. The following interactions were found to be significant for methane conversion: M*τ, F*τ and M*F. The interaction of F*τ also affected the hydrogen yield. The third-order interaction of F*τ*M was also found to be statistically significant. The optimum methane conversion value of 57.36% could be obtained by setting switching time, total flow rate and a mole fraction of methane of 4.24 minutes, 543ml/min and 0.6043, respectively. The optimum value of hydrogen yield of 36.73% was reached by setting total flow rate, mole fraction of methane and switching time of 540ml/min, 0.5845 and 4.15 minutes, respectively. The analysis of reactor operation showed that optimization of the system required changing more than one factor and that there is a complex interplay of the different experimental factors. The influence of the factors may all be interpreted in terms of heat release and heat loss in the system.

Enhanced acetoin production by Serratia marcescens H32 using statistical optimization and a two-stage agitation speed control strategy

Enhanced acetoin production was carried out by Serratia marcescens H32. First, medium compositions were optimized statistically for shake flask fermentations to produce acetoin. Sucrose and corn steep liquor powder (CSLP) were identified as the most significant factors by Plackett-Burman design. The path of steepest ascent and response surface methodology were then employed to determine the optimal concentrations of the two factors. Acetoin yield was up to 41.5 g/L in flask fermentations using the optimized medium. Furthermore, the optimal medium was used to conduct fermentation experiments in a 3.7-L bioreactor. The influences of different agitation speeds on acetoin production were investigated. Based on a process analysis, a two-stage agitation speed control strategy was proposed, in which the agitation speed was controlled at 700 rpm during the first 8 h and then switched to 600 rpm. A relatively high acetoin concentration (44.9 g/L) and high acetoin productivity (1.73 g/L/h) were achieved by applying this strategy. Fed-batch fermentation based on the two-stage agitation speed control strategy was performed, and a maximum acetoin concentration of 60.5 g/L with productivity of 1.44 g/L/h was achieved.

Optimization and scale-up of 2,3-butanediol production by Bacillus amyloliquefaciens B10-127

The effects of culture conditions on 2,3-butanediol (2,3-BD) production and its possible scale-up have been studied. A newly isolated Bacillus amyloliquefaciens B10-127, belonged to GRAS microorganisms and showed a remarkable 2,3-BD producing potency, was used for this experiment. Corn steep liquor, soybean meal and ammonium citrate were found to be the key factors in the fermentation according to the results obtained from the Plackett-Burman experimental design. The optimal concentration range of the three factors was examined by the steepest ascent path, and their optimal concentration were further optimized via response surface methodological approach and determined to be 31.9, 22.0 and 5.58 g/l, respectively. The concentration of the obtained 2,3-BD increased significantly with optimized medium (62.7 g/l) when compared with unoptimized medium (45.7 g/l) and the 2,3-BD productivity was about 2.4-fold (The fermentation time was shorten from 72 to 42 h). To observe scale-up effects, batch fermentation was carried out at various working volumes. At a working volume of 20.0 l, the final 2,3-BD concentration and yield were 61.4 and 0.38 g/g at 36 h with a 2,3-BD productivity of 1.71 g/l h. This result shows similar amount of 2,3-BD obtained in lab-scale fermentation, and it is possible to scale up to larger fermentors without major problems.

Optimization of the Medium Composition of &lt;i&gt;Lactobacillus Rhamnous&lt;/i&gt; NCU239

MRS culture medium was used as the basic medium for optimizing the fermented condition of Lactobacillus. rhamnosus. The four significant factors (beef extract, tween-80, peptone, diammonium citrate) were screened from these components by using a Plackeet-Burman design. Steepest ascent path was adopted to approach the optimal region, and then the Central Composite Design was used to determine the optimal levels of the main factors. Considering the fit model, cost and operation, the optimal conditions were determined as follows: beef extract 2.6%, tween-80 0.3%, peptone 2%, diammonium citrate 0.4%, with other components remaining the same, 3% inoculation, 18h culture at 37¡æ.Under such conditions, the experimental value of cell concentration were 3.54×109cfu/ml and 2.19-fold live bacteria counts in MRS-based culture medium, showing no difference with predicted value 3.68×109cfu/ml.

English

&nbsp; The objective was to develop an optimal, albeit low-cost medium for bacteriocin production, thereby facilitating industrial production. Soybean meal and peptide, two low-cost nitrogen sources often applied in industrial fermentation, were used to replace their expensive counterparts in De Man Rogosa and Sharpe (MRS). Two factors were first chosen from the 11 considered in the Plankett-Burman (PB) design. Then, the path of steepest ascent and central composite design (CCD) were used to approach the optimum region of the response and determine the maximum activity of the bacteriocin. Optimal concentration of glucose (36.3 g/l) and NaCl (1.41 g/l) stimulated the production of bacteriocins. And the optimal equation was then verified by 50 L fermentor. Under optimized conditions,&nbsp;Lactobacillus plantarum&nbsp;YJG produced a 1.4 fold higher production of bacteriocin than the common MRS, with 40.6% cost savings relative to non-optimized conditions. &nbsp; Key words:&nbsp;Lactobacillus plantarum&nbsp;YJG, bacteriocin, response surface methodology, central composite design, optimization.

Statistical optimization of chitosanase production by Aspergillus sp. QD-2 in submerged fermentation

Cultivation of chitosanase production by Aspergillus sp. QD-2 under submerged fermentation was optimized. Factors including (NH4)2SO4, inoculum size and initial pH were identified by two-level Plackett-Burman design (PBD) as significant for chitosanase production. The path of steepest ascent was undertaken to determine the optimal region of three significant factors. To determine the optimal values of the significant variables, Box-Behnken design (BBD) and response surface analysis were employed. The quadratic regression model of producing chitosanase showed that the optimal cultivation conditions ((NH4)2SO4 5.164 g/l, inoculum size 8.204% (v/v) and initial pH 4.074) resulted in the improvement of chitosanase activity (85.816 U/ml) as compared to the initial level (26.515 U/ml) after 72 h of fermentation. The optimal pH and temperature of the crude chitosanase were determined to be 5.6 and 55°C, respectively.

The role of environmental factors and medium composition on bacteriocin production by an aquaculture probiotic Enterococcus faecium MC13 isolated from fish intestine

The aim of this study was to optimize medium composition for higher yield of total viable cells and bacteriocin by Enterococcus faecium MC13. The factors such as peptone, meat extract, yeast extract, lactose, glycerol, tween 80, triammonium citrate and K2HPO4 were selected based on the Lactobacillus MRS medium composition. Two level factorial designs (FD) and steepest ascent path were performed to identify vital factors among the variables. Through the 2−8 FD, peptone, yeast extract and lactose were found to be significant factors involved in the enhanced production of viable cells and bacteriocin. Therefore, these three foremost factors were further optimized by central composite design to achieve efficient yield. The optimum MRS composition was found to be peptone (40.0 g/L), meat extract (30.0 g/L), yeast extract (40.0 g/L), lactose (24.0 g/L), glycerol (5.8 g/L), Tween 80 (3.0 g/L), triammonium citrate (1.0 g/L), K2HPO4 (2.5 g/L), MgSO4·7H2O (0.10 g/L), MnSO4·7H2O (0.05 g/L) and dipotassium PO4 (2.0 g/L). The optimized growth medium allowed higher amount of bacteriocin activity (36,100 AUml−1) and total viable cells (14.22 LogCFUml−1) production which were two-times higher than the commercial MRS medium.

Steepest-ascent constrained simultaneous perturbation for multiobjective optimization

The simultaneous optimization of multiple responses in a dynamic system is challenging. When a response has a known gradient, it is often easily improved along the path of steepest ascent. On the contrary, a stochastic approximation technique may be used when the gradient is unknown or costly to obtain. We consider the problem of optimizing multiple responses in which the gradient is known for only one response. We propose a hybrid approach for this problem, called simultaneous perturbation stochastic approximation steepest ascent , SPSA-SA or SP(SA) 2 for short. SP(SA) 2 is an SPSA technique that leverages information about the known gradient to constrain the perturbations used to approximate the others. We apply SP(SA) 2 to the cross-layer optimization of throughput, packet loss, and end-to-end delay in a mobile ad hoc network (MANET), a self-organizing wireless network. The results show that SP(SA) 2 achieves higher throughput and lower packet loss and end-to-end delay than the steepest ascent, SPSA, and the Nelder--Mead stochastic approximation approaches. It also reduces the cost in the number of iterations to perform the optimization.