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Central Composite Experimental Design (central + composite_experimental_design)
Selected AbstractsOptimization of Medium Composition for Nisin Fermentation with Response Surface MethodologyJOURNAL OF FOOD SCIENCE, Issue 6 2008X.-X. Zhou ABSTRACT:, Nisin is an effective food biopreservative widely used in food industry. However, 1 problem of concern is limited production rate and final nisin concentration. A nisin-producing strain, L. lactis Lac2, a mutant strain with high yield of nisin, was obtained in our laboratory recently. In the present study, a fractional factorial design was applied to investigate the main factors that affect the yield of L. lactis Lac2. Central composite experimental design and response surface methodology were adopted to derive a statistical model for optimizing the composition of the medium. The results showed that the optimum medium for nisin production of L. lactis Lac2 was composed of 2.68% sucrose (w/v), 0.5% tryptone (w/v), 1% yeast extract (w/v), 0.3% Tween-80 (w/v), 0.02% MgSO4·7H2O (w/v), 0.81% NaCl (w/v), 1.91% K2HPO4 (w/v), 0.05% ascorbic acid (w/v), and 2% agar (w/v) (if necessary) at pH 6.5. When cultured in the optimum medium, the nisin yield is an average of 3381.81 IU/mL, which nearly doubled the yield when incubated in the initial medium. Also, the concentration of tryptone was decreased while that of the sucrose was increased when compared with CM broth, which means a reduction of the fermentation cost. [source] OPTIMAL CONDITIONS FOR THE GROWTH AND POLYSACCHARIDE PRODUCTION BY HYPSIZIGUS MARMOREUS IN SUBMERGED CULTUREJOURNAL OF FOOD PROCESSING AND PRESERVATION, Issue 4 2009PING WANG ABSTRACTS In submerged cultivation, many nutrient variables and environmental conditions have great influence on the growth and polysaccharide production by Hypsizigus marmoreus. Plackett,Burman design was used to determine the important nutrient factors. A central composite experimental design and surface response methodology were employed to optimize the factor levels. Prediction models for dry cell weight (DCW), polysaccharide outside cells (EPS) and polysaccharide inside cells (IPS) under important nutrient conditions were developed by multiple regression analysis and verified. By solving the equations, the optimal nutrient conditions for highest EPS production (9.62 g/L) were obtained at 6.77 g cornstarch/L, 36.57 g glucose/L, 3.5 g MgSO4/L and 6.14 g bean cake powder/L, under which DCW and IPS were 16.2 g/L and 1.46 g/L, close to the highest value under their corresponding optimal conditions. Optimal environmental conditions were obtained at 10% inoculation dose, 45 mL medium in a 250 mL flask, pH 6.5, 25C and 200 rpm according to the results of single-factor experiment design. PRACTICAL APPLICATIONS Hypsizigus marmoreus polysaccharides have many functional properties, including antitumor, antifungal and antiproliferative activities, and free-radical scavenging. Liquid cultivation could produce a higher yield of polysaccharides and more flexible sequential processing methods of H. marmoreus, compared with traditional solid-state cultivation. However, the cell growth and production of polysaccharides would be influenced by many factors, including nutrient conditions and environmental conditions in the liquid cultivation of H. marmoreus. Keeping the conditions at optimal levels can maximize the yield of polysaccharides. The study not only found out the optimal nutrient conditions and environmental conditions for highest cell growth and yield of polysaccharides, but also developed prediction models for these parameters with important nutrient variables. Yield of polysaccharide inside of cells was also studied as well as polysaccharides outside of cells and cell growth. The results provide essential information for production of H. marmoreus polysaccharides by liquid culture. [source] RHEOLOGICAL PROPERTIES, WHEY SEPARATION, AND MICROSTRUCTURE IN SET-STYLE YOGURT: EFFECTS OF HEATING TEMPERATURE AND INCUBATION TEMPERATUREJOURNAL OF TEXTURE STUDIES, Issue 5-6 2003WON-JAE LEE The effects of heat treatment and incubation temperature on the rheological and microstructural properties of yogurt were studied. A central composite experimental design and response surface methodology were used for data analysis. The rheological properties were determined by dynamic low amplitude oscillation and the amount of spontaneous whey separation was quantified by the volumetric flask test. Confocal scanning laser microscopy was used to examine the gel structure. The storage moduli of yogurts increased with an increase in heating temperature and a decrease in incubation temperature. The maximum loss tangent value during gelation, permeability, and amount of spontaneous whey separation of yogurts increased with a decrease in heating temperature and with an increase in incubation temperature. These parameters indicated an increased possibility for rearrangements, which was confirmed by presence of large pores in the gel network. Second order polynomial models successfully predicted the effects of heating temperature and incubation temperature on the rheological properties, permeability, and whey separation of yogurts. Whey separation was negatively correlated with storage modulus (r= -0.66), and was positively correlated with the maximum loss tangent (r= 0.63) and permeability (r= 0.78). This study demonstrates that weak yogurt gels, which have high loss tangent values, favor rearrangements in the network and the resulting network has larger pores (high permeability) and exhibits greater whey separation. [source] A response surface methodology approach to optimise pretreatments to prevent enzymatic browning in potato (Solanum tuberosum L) cubesJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 1 2002C Reyes-Moreno Abstract The objective of this work was to find the best combinations of ascorbic acid concentration/soaking time (Pretreatment 1), 4-hexylresorcinol concentration/soaking time (Pretreatment 2) and ascorbic acid concentration,4-hexylresorcinol concentration/soaking time (Pretreatment 3) to prevent the development of enzymatic browning in raw potato cubes (10,mm,×,10,mm,×,10,mm). Potato variety Alpha was used as study model because of its low susceptibility to enzymatic browning. Response surface methodology was applied in all pretreatments on two response variables (Hunter L value and total colour difference) to find the best conditions for carrying out the pretreatments. The various pretreatments had variation levels for ascorbic acid (AA) concentration (1 and 3) and 4-hexylresorcinol (4HR) concentration (2 and 3) of 1,4 and 0.04,0.20,g,l,1 respectively; in all pretreatments the variation level for soaking time was 3,6,h. A central composite experimental design with two factors at five levels was used. Predictive models for Hunter L value and total colour difference were developed as a function of process or independent variables. The optimisation technique was applied to obtain maximum Hunter L values and minimum values of total colour difference. Surface superposition of these variables allowed identification of the best combinations of process variables for each pretreatment as (1) 2.9,g,l,1 AA/4.8,h, (2) 0.04,g,l,1 4HR/2.6,h and (3) 2.42,g,l,1 AA,0.15,g,l,1 4HR/5.41,h. © 2001 Society of Chemical Industry [source] Effect of the addition of calcium hydroxide on some characteristics of extruded products from blue maize (Zea mays L) using response surface methodologyJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 14 2001José J Zazueta-Morales Abstract The aim of this research was to study the effects of calcium hydroxide (0,0.2%) and screw speed (100,180,rpm) on the expansion index (EI), bulk density (BD), penetration force (PF) and specific mechanical energy (SME) values of blue maize meal extrudates. Blue maize meal was extruded using a commercial extruder (Brabender 20DN/8-235-00) with a compression screw ratio of 3:1. A second-order, central composite experimental design was used. It was found that the EI and SME values decreased and the BD and PF values increased when the calcium hydroxide concentration was increased. The screw speed had a significant effect only on the SME and PF values. Quadratic model fitness was shown for all responses, with values of R2,>,0.74, p of F (model) <0.01 and variability coefficient <13.3% (except for PF, 29.18%), and for almost all cases there was no lack of fit (p,>,0.055). Calcium hydroxide concentration showed good correlation (p,<,0.01) with EI (r,,=,,0.81), PF (r,,=,0.60), SME (r,,=,,0.76) and BD (r,,=,0.83). However, screw speed was marginally or not correlated (r,<,0.36, p,>,0.14) with the responses. The results suggest that it is possible to produce appropriate extruded products from blue maize fortified with calcium in an optimised calcium hydroxide concentration and screw speed range of 0.02,0.078% and 117,180,rpm respectively. © 2001 Society of Chemical Industry [source] Response surface methodology for optimizing the fermentation medium of Clostridium butyricumLETTERS IN APPLIED MICROBIOLOGY, Issue 4 2004G.Q. He Abstract Aims:, Strains of Clostridium butyricum have been increasingly used as probiotics for both animals and humans. The aim of this study was to develop a growth medium for cultivating C. butyricum ZJUCB using a statistical methodology. Methods and Results:, Response surface methodology (RSM) was used to evaluate the effects of variables, namely the concentrations of the glucose, pectin, soyabean cake extract, casein, corn steep flour, ammonium sulphate, sodium bicarbonate and the medium initial pH. A fractional factorial design was applied to study the main factors that affected the growth of a probiotic strain of C. butyricum currently preserved in our lab and the central composite experimental design was adopted to derive a statistical model for optimizing the composition of the fermentation medium. The experimental results showed that the optimum fermentation medium for the growth of C. butyricum was composed of 2% glucose (w/v), 0·5% pectin (w/v), 0·2% casein (w/v), 3·98% soyabean cake extract, 0·1% (NH4)2SO4 (w/v), 0·124% NaHCO3 (w/v), 0·37% corn steep flour (w/v), 0·02% MnSO4 H2O (w/v), 0·02% MgSO4 7H2O (w/v) and 0·002% CaCl2 (w/v) at pH 7·5. Conclusions:, After incubating 24 h in the optimum fermentation medium, the populations of the viable organisms were estimated to be 109 CFU ml,1. In the present study, we report the optimization of a growth medium that produced increased yields using statistical approach. Significance and Impact of the Study:, The use of bacteria as a probiotic is showing increasing potential. The development of a growth medium that has a high yield is an obvious need, and the approach to optimizing a growth medium is innovative. [source] Response surface modeling and optimization for production of ammonia from urea in a batch reactorASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 4 2009J. N. Sahu Abstract Ammonia is applied to removal of NOx contaminates contained in a flue gas stream from energy producing boilers and increase of efficiency of an electrostatic precipitator for removal of fly ash from flue gas stream from a boiler using fossil fuel. In this study, urea hydrolysis for production of ammonia, in different application areas that requires safe use of ammonia, was investigated in a batch reactor. The single and combined effects of operating parameters such as initial feed concentrations, temperature, time and stirring speed on the production of ammonia from urea were analyzed using response surface methodology (RSM). A 24 full factorial central composite experimental design was employed. Analysis of variance (ANOVA) showed a high coefficient of determination value (R2 = 0.976) and satisfactory prediction second-order regression model was derived. The optimum production conditions were determined as temperature, 180 °C; initial feed concentrations, 22.24 wt% of urea; time, 74.9 min and stirring speed, 1150 rpm. At optimum conversion conditions, the conversion of urea for production of ammonia was found to be 75.65%. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source] | ||||||||||