Optimization of chitosanase production from Bacillus sp. RKY3 using statistical experimental designs

BACKGROUND: The culture medium and fermentation conditions for the production of constitutive chitosanase from a newly isolated Bacillus sp. RKY3 were optimized statistically. RESULTS: The variables significantly influencing both chitosanase production and cell growth were screened through the Plackett–Burman design, by which maltose, beef extract, MgSO₄, and incubation time were identified as the most significant variables. The optimum values of the selected variables and their mutual interactions were determined through the steepest ascent method and Box–Behnken experimental design. The results demonstrated that 62.30 U mL^?1 chitosanase activity was predicted with optimum conditions of maltose (30.18 g L^?1), beef extract (15.25 g L^?1), MgSO₄ (0.26 g L^?1), and incubation time (50.02 h). The predicted response was verified by the validation experiments, and the optimum conditions resulted in a maximum chitosanase activity of 63.53 ± 1.22 U mL^?1. CONCLUSION: The optimization of fermentation variables resulted in an approximately 11.3‐fold increase in chitosanase activity compared with that observed under unoptimized conditions (from 5.63 U mL^?1 to 63.53 U mL^?1). Copyright © 2009 Society of Chemical Industry     

Comparison of experimental designs using neural networks

Experimental designs were compared using stacked‐layer feed‐forward neural networks. Several traditional three‐level designs and uniform designs were investigated using three‐factor linear and nonlinear models. The prediction error was found to be inversely proportional to the number of experiments. Uniform designs displayed better performance than traditional three‐level designs for the same number of experiments. The sum of squares of prediction errors was generally smaller for uniform designs. The performance difference between three‐level designs and uniform designs was attributed to the number of factor levels. This was confirmed by further investigation on random designs with more factor levels.     

Modeling and optimization of cutinase production by recombinant Escherichia coli based on statistical experimental designs

Statistics-based experiment designs were used to optimize the culture medium (glucose, yeast extract, IPTG, tween-60, and CaCl₂) for cutinase production by recombinant Escherichia coli. A 2^5-1 fractional factorial design augmented with center points revealed that glucose, yeast extract, and IPTG were the most significant factors, whereas the other factors were not important within the levels tested. The method of steepest ascent was used to approach the proximity of optimum, followed by a central composite design to develop a response surface for culture condition optimization. The optimum culture medium for cutinase production was found to be: glucose 33. 92 g/L, yeast extract 30.92 g/L, and IPTG 0.76 g/L. A cutinase production of 145.27±1.5 U/mL, which was in agreement with the prediction, was observed in triplicate verification experiments. The results obtained here verified the effectiveness of the applied methodology and may be helpful for cutinase production on an industrial scale.     

Intensification and optimization of the characteristics of polyacrylonitrile nanofiltration membranes with improved performance through experimental design and statistical analysis

The present study aims to employ experimental design and statistical analysis in order to investigate in detail the effect of various prominent parameters on the characteristics and performance of polyacrylonitrile nanofiltration membranes for the treatment of electroplating wastewaters targeting Ni, Cr, and Zn ions. Incorporation of TiO₂ into the membrane matrix was effective in improving pure water flux (PWF) by ~16%. Also, PWF and Ni rejection of membranes escalated to 118.55 L m⁻² h⁻¹ and 90.79%, respectively upon addition of 1.5 wt% citric acid to the dope. Variation in coagulation bath temperature from 25°C to 45°C led to the formation of membranes having higher porosity with enhanced PWF by about 25% at the expense of only 5% reduction in Ni rejection. Parameters were optimized by analysis of variance (ANOVA). In contrast to the effect of feed concentration, an increase in feed pressure and pH enhanced permeate flux and total ion rejection. Similarly, permeate flux increased at higher operational temperatures without change in total rejection. A mathematical model was developed by applying ANOVA and the best combination of operating parameters was obtained by optimization.     

Influence of surfactants and experimental variables on the viscosity characteristics of coal water mixtures

To improve the fluidity of a coal water mixture (CWM) having lower viscosity and higher solid concentration, the effects of surfactants (five kinds) and experimental variables such as temperature (5-65 °C), pH (1-11), particle size distribution (PSD) on the viscosity characteristics of two different coals (Shenhua and Kideco Coal) were investigated. Relatively economical surfactants were chosen in this study: sulfonated melamine formaldehyde polymer (SMF-30), naphthalene formaldehyde sulfonate (Sikament-NN), naphthalene sulfonate water reducer (NSWR), naphthalene formaldehyde sulfonate (PC-1000) and poly-carboxylate (PC). The SMF-30, an anionic surfactant, revealed the most significant reduction in viscosity of CWM among the five surfactants since the SMF-30 forms electric double layer on the surface of coal, and the repulsive force of this layer surpasses the aggregation of coal particles. In addition, the viscosity of CWM decreased with increasing pH and temperature, in particular, the increase in OH- on the surface of coals by the addition of NaOH caused the increase in the repulsive force between the negatively charged coal particles. Furthermore, the very fine particles (less than 45 μm) of coals should be removed before making CWMs since it revealed the increase in viscosity of CWMs.     

Experimental and statistical study of the effects of material properties,curing agents,and process variables on the production of thermoplastic vulcanizates

A comprehensive experimental study together with statistical analysis was performed to identify the optimal process conditions, materials selection, and curing system for the production of thermoplastic vulcanizates (TPVs) based on EPDM rubber and polypropylene. Two types of curing systems were studied together with five different types of EPDM rubber. The TPV products were assessed according to elastic modulus and degree of swelling (indicators of crosslink density), ultimate tensile strength, ultimate elongation, tear strength, and compression set. A design of experiments method was applied to minimize the number of experiments and to obtain response surface and regression models for this complex and highly interactive system. From the modeling results, optimum values for the influential factors were obtained to achieve the target end product properties. It was found that a phenolic resin‐based curing system gave the best product properties and that the most influential factors were the rubber characteristics (ethylene content, ethylidene norbornene content, and molecular weight) and the polypropylene content in the formulation. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

A study on the effects of reaction conditions on the characteristics of resol resins for foams by statistical analysis

A two-level full factorial experimental design with three variables, formaldehyde-to-phenol (F/P) molar ratios, hydroxy-to-phenol (OH/P) wt%, and reaction temperature was implemented to determine the effect of the variables on the properties of phenol-formaldehyde (PF) resol resins for insulation foam. Ten resins were prepared with F/P molar ratios between 1.5 and 2.5, OH/P wt% between 0.5 and 1.5 and reaction temperature between 80 and 90 ‡C. The effect of three independent variables on the resin properties was analyzed by using three-way ANOVA of SPSS. All three production variables had a significant effect on resin properties. The F/P molar ratio and OH/P wt% were found to have the most frequent effect on resin properties. F/P molar ratio and OH/P wt% had an increasing effect, while reaction temperature showed a decreasing effect on free formaldehyde. The present study confirms that experimental design is a very valuable and capable tool for evaluating multiple variables in resin production.     

Development of rapid-set high-strength cement using statistical experimental design

Many applications like aircraft runway, busy roads, highway or motorways, water tank repair, etc. demand a cement that sets fast and gains the required strength in a few hours. Though there are few cements available to meet the requirements given above, most of them are very costly, like magnesium phosphate cement, jet cement, geopolymeric cement, etc. So, an attempt has been made to make cost-effective rapid-set high-strength cement having initial setting time of ∼15 min, final setting time of ∼30 min, 4 h cold compressive strength (CCS) of ∼12 MPa (minimum), 8 h CCS of ∼24 MPa and 1 day CCS of ∼40 MPa for the neat cement. The experiments were designed using orthogonal array technique in L₉ array with three factors, namely OPC/high-alumina cement/anhydrous calcium sulphate, fineness of the cement, and type of additives, at three levels each. The responses studied are initial setting time, final setting time, and CCS after 4, 8, and 24 h curing. The response data were analysed using analysis of variance (ANOVA) technique with a software package, ANOVA by Taguchi Method (ATM). In the case of setting time, fineness of the cement and OPC/HAC/anhydrous calcium sulphate ratio plays a significant role. Additive type and the OPC/HAC/anhydrous calcium sulphate are significant factors affecting the CCS at different ages. The confirmatory trial results clearly indicate that the setting time and CCS at different ages targeted were achieved using design of experiments.     

Comparative study of the effects of experimental variables on growth rates of aluminum and iron hydroxide flocs during coagulation and their structural characteristics

In this study, the dimensions of over six thousand flocs were analyzed to quantitatively and comparatively investigate the effects of several experimental variables on the growth rate of aluminum (Al) and ferric (Fe) hydroxide flocs. Results show that Fe hydroxide flocs have faster growth rate than Al hydroxide flocs; and the average size of the former is larger than that of the latter. Increasing the concentration of the bivalent sulfate ion (SO₄²⁻), initial turbidity, or slow mixing rate, was able to increase the growth rate of both kinds of flocs. On the other hand, steady floc sizes were found to decrease with the increase in SO₄²⁻ concentration, initial turbidity, or shear rate. Fe hydroxide flocs are more prone to be influenced by the changes in the variables than Al hydroxide flocs. While the steady floc sizes became smaller when initial turbidity or slow mixing speed increased, the roundness and smoothness of flocs were found to increase, indicating that higher initial turbidity or larger slow mixing rate produces flocs with more regular and round shape. Furthermore, at a fixed shear rate, Fe hydroxide flocs are stronger than Al hydroxide flocs. However, Fe hydroxide floc sizes are much easier to decrease with the increase in slow mixing intensity.     

Glass foams produced by glass waste,sodium hydroxide,and borax with several pore structures using factorial designs

Glass foams have great potential for several technological applications, for example, filters and thermal or acoustic insulators. Sodium hydroxide is an efficient foaming agent to obtain glass foams with high level of porosity. However, the control of variables that influences on structure, type, and size of pores of glass foams is necessary. This study evaluates the influence of composition and process parameters on glass foams based on soda-lime glass waste, sodium hydroxide, and borax. Experiments were conducted using factorial designs. According to the experimental conditions, bulk density varied from 0.16 to 0.79 g cm⁻³ and maximum porosity of 92%. Amounts of NaOH and borax in addition to sintering temperature are the main variables of the foaming process. The role of NaOH content is to reduce the density and closed porosity of glass foams associated with an increase in their open porosity. The addition of borax with low NaOH amount promoted densification and pore closure in glass foams. NaOH and borax content allows controlling the type of predominant porosity on foams (open or closed porosity). Glass foams were resistant to sulfuric acid, hydrochloric acid, and nitric acid in diluted solutions. These results allow controlling the pore structure of glass foams for different applications.     

废水中COD分光光度法操作条件的确定

对影响分光光度法测废水中COD的因素进行研究,确定方法的操作条件并进行验证.试验结果表明:本法简单、快速、节省试剂、结果可靠.     

A statistical approach for estimation of significant variables in wet attrition milling

Production of ultrafine particles by grinding in attritor mill has been successfully applied in chemical, pharmaceutical and mineral processing industries. It has also been demonstrated as a cost effective and efficient method for production of nanoparticles. The present study attempts to relate the effects of operating variables on the Rosin Rammler equation parameter (X_d), which is indicative of the size of product. Operating parameters considered for the investigation are initial size of particles, ball loading, slurry mass fraction, diameter of grinding media, pin tip velocity and ratio of Young's modulus. The results indicate that the ratio of Young's modulus and initial size of particles have significant effects; ball loading, diameter of grinding media and pin tip velocity have moderate effects; and slurry mass fraction does not have a significant effect on the final size of the powder. The paper illustrates how statistical analysis, when appropriately applied, can be used to analyze complex unit operations such as the attritor mill and can be effective in gathering of process understanding.     

Analysis of individual and interaction effects of processing parameters on wet grinding performance in ball milling of alumina ceramics using statistical methods

It is of great interest and necessary to closely investigate and understand how ball milling parameters can affect the overall quality of milled ceramic powders. In this paper, we analyzed the individual and interaction effects of the key processing parameters on the wet grinding performance in a ball mill for alumina powder using statistical methods. The grinding performance was evaluated based on three quality characteristics of milled alumina powder: the median particle size (d₅₀), width and skewness reflecting the shape of particle size distributions (PSDs). For this determination, the volume percentage of slurry, solid content, milling speed, milling time, and ball size are regarded as the key parameters affecting these characteristics. Milling experiments were designed by central composite design, and an experimental dataset was collected systematically. The analysis results show that it is worthwhile to consider not only the d₅₀ but also the shape of the PSDs when assessing the ball milling performance. These results are useful for the production of high-quality alumina powders in ceramic industries.     

Effects of experimental variables on the synthesis of porous matrices

Macroporous beads, poly(ethylene glycol dimethacrylate‐co‐acrylic acid) [poly(EGDMA‐co‐AAc)], and poly(ethylene glycol dimethacrylate‐co‐hydroxyethyl methacrylate) [poly(EGDMA‐co‐HEMA)] were prepared by the suspension polymerization technique in the presence of a porogen agent. Different experimental conditions such as amount of initiator, porogen type, and temperature were studied to optimize the polymerization systems. These hydrophilic copolymers were characterized by IR spectroscopy, scanning electron microscopy, specific surface area, and swelling in water. A new parameter, H, defined as the ratio between the equilibrium weight swelling ratio (q_w) and equilibrium volume swelling ratio (q_v), allowed to select the reaction conditions from which matrices with high capacity of water sorption and low stretching degree were reached. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 920–927, 2001     

浅谈几种钢丝编织机的结构原理及性能特点

介绍了国产GBG，美国RB-2、TMW225-11，德国MR-11，意大利DAK，韩国BW等型号的钢丝编织机的编织机构的结构特点，分析了各种编织机梭子的传递过程。随后总结了各种编织机的性能特点并进行了分析讨论，认为至今没有先进的国产编织机研发成功的主要原因在于成本价格过高及制造技术水平达不到。     

Statistical analysis of effects of experimental variables on mass transfer coefficient in a novel hybrid bubble column using Box–Behnken design

Statistical analysis of effects of experimental variables on volumetric mass transfer coefficient in a novel hybrid rotating and reciprocating perforated plate bubble column is studied. The novel bubble column is designed indigenously using bevel gear arrangement. Agitation level, superficial gas velocity, superficial liquid velocity, perforation diameter and plate spacing are the experimental variables. Air–sodium sulphite solution system is used in this investigation. The Box–Behnken design in response surface methodology is employed for statistical analysis. The relationship between experimental variables and the desired response of volumetric mass transfer coefficient is established for this novel hybrid column. The linear, quadratic and interactive effects of experimental variables are found to be significant on the desired response of volumetric mass transfer coefficient. Results show that the data adequately fit into the second‐order polynomial model. An F‐test and P‐value show the significance of parameters on volumetric mass transfer coefficient. © 2012 Canadian Society for Chemical Engineering     

A statistical evaluation of preparation conditions on the performance of Ce-promoted Co-Mo Fischer-Tropsch catalyst

This paper describes a statistical approach to the optimal selection of preparation conditions for a ceria-promoted Co-Mo catalyst used during CO hydrogenation. Eight catalyst samples based on a full factorial design were prepared via incipient wetness method. Evaluation was carried out in laboratory packed bed reactor using synthesis gas containing H₂:CO=2 at 280 °C and 110 kPa. BET was unaffected by pH although increased calcination temperature induced only a small drop in total surface area. More significantly, catalysts calcined at low temperature (350 °C) suffered a 3-fold loss in metal surface area when treated at high temperatures (550 °C) while an increase in pH improved the metal area value. pH values above the isoelectric point (IEP=5.65) and low calcination temperature favoured activity and alkene selectivity. High reduction temperature, however, appeared to enhance methane suppression. Additionally, 2-factor interactions were statistically more significant than 3-factor interactions at 95% confidence level. Optimisation of the polynomial models describing the response data was also consistent with qualitative inferences. This paper was presented at the 8th APCChE (Asia Pacific Confederation of Chemical Engineering) Congress held at Seoul between August 16 and 19, 1999.     

Effects of experimental variables on phosphate adsorption on bentonite

The adsorption process of phosphate ions on a bentonite from Almería (East-Andalucía, Spain) was studied at 30°C over a range of experimental conditions such as saline (0.1 M KCl) or non-saline medium, natural or calcium homoionic bentonite and different pH values. In order to calculate the adsorption capacities (X_m) of the samples, the experimental data points were fitted to the Langmuir equation. X_m values ranged from 0.42 μg P g^?1 for the natural sample in non-saline medium to 0.74 μg P g^?1 for the same sample in saline medium, the X_m value corresponding to the calcium homoionic bentonite sample being intermediate. At different pH conditions, X_m increased from 0.28 μg P g^?1 at a pH of 1.3 to 1.53 μg P g^?1 at a pH of 4.4, and then decreased to 0.42 μg P g^?1 at a pH of 8.7.     

Investigation of the effects of several porosity variation profiles on performance and pollutants emission of the porous media burners

This paper presents results of numerical investigation on the effect of using variable porosity porous media burner on its performance and pollutant emission. A two‐dimensional axisymmetric model for premixed methane/air combustion in porous media has been developed. This code solves the continuity, Navier Stokes, solid and gas energies, and chemical species transport equations using the finite volume method. The pressure and velocity have been coupled with the SIMPLE algorithm. In this paper, the results of applying two different profiles of porosity instead of constant porosity for two zones of burner have been presented. The results showed that by applying porosity variation along the burner, the peak temperature can be decreased about 4.5%, and subsequently, the amount of exhaust pollutants such as NO_x can also be decreased while increase in pressure losses along the burner is negligible. In addition, the effects of excess air ratio, volumetric heat transfer coefficient, inlet velocity, chemical kinetics, conductivity coefficient, and wall temperature on the porous media burners with variation of porosity are investigated. Copyright © 2014 John Wiley & Sons, Ltd.