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Agitation Speed (agitation + speed)
Selected AbstractsPalladium and platinum sorption on a thiocarbamoyl-derivative of chitosanJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2010A. Butewicz Abstract Immobilizing thiourea onto chitosan allowed using the polymer for the recovery of platinum groups metals (PGMs) in acidic solutions (up to 1,2M HCl concentrations). At low HCl concentration protonated amine groups may sorb chloroanionic metal species (electrostatic attraction mechanism); however, most of sorption proceeds through chelation on sulfur containing groups (less sensitive to acidic conditions). The bi-site Langmuir equation was used for fitting sorption isotherms. The sorption of PGMs was weakly affected by the composition of the solution (presence of high concentration of anions and base metals). Maximum sorption capacities for Pd(II) and Pt(IV) ranged between 274 and 330 mg g,1 in 0.25M HCl solutions and decreased to 150,198 mg g,1 in 2M HCl solutions: Pd(II) sorption was systematically higher than Pt(IV) sorption. The pseudo-second rate equation was used for modeling the uptake kinetics. Agitation speed hardly affected uptake kinetics indicating that external diffusion resistance is not the rate controlling step. Desorption yield higher than 85% were obtained using thiourea in 0.1M HCl solution. The adsorbents could be reused for at least three cycles. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Metastable zone determination of lipid systems: Ultrasound velocity versus optical back-reflectance measurementsEUROPEAN JOURNAL OF LIPID SCIENCE AND TECHNOLOGY, Issue 5 2010Kesarin Chaleepa Abstract The metastable zone width (MZW) of a multi-component system as influenced by the process parameters cooling rate, agitation speed, and additive concentration was determined via ultrasound velocity measurements. The results were compared with those obtained by optical back-reflectance measurements (ORM) using coconut oil as a model substance. Increasing the cooling rate led to the shift of the nucleation point to lower temperatures. This tendency was better visualized by the ultrasonic curves while a significant disturbance of the ORM signal could be observed. Agitation led to an increase of the nucleation temperature and hence a narrower metastable zone. The influence of an additive on the MZW was found to strongly depend on its concentration. The MZW detected by the ultrasound technique was narrower compared to that obtained by the ORM method, indicating the faster response to the phase transition of the ultrasound technique. Another advantage of the ultrasound technique was the in situ evaluation of the experimental data, while ORM needed a linear fitting to estimate the saturation temperature. Furthermore, ultrasound velocity measurements are based on density determination of the medium whereas the ORM sensor is able to detect only particles that are located within the measuring zone and possess a well-defined size. Practical applications: MZW is one of the most important parameters that determine the characteristics of crystalline products. However, a proper technique that can be used in MZW detection in fat systems has rarely been reported, due to the difficulties in dealing with natural fats. The findings of this study can greatly help those who are involved in the field of fat crystallization from both the academic and the practical point of view. This is due to the fact that new and promising techniques for the online and in situ determination of the MZW of fats, with high accuracy, and reproducibility, under most process conditions, were clarified in this work. The readers can easily follow the procedure developed in this paper. Also information about the influence of process parameters and additives on the MZW is included. [source] Regioselective C-6 Hydrolysis of Methyl O -Benzoyl-pyranosides Catalysed by Candida Rugosa LipaseEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 10 2009Aslan Esmurziev Abstract Hydrolysis of six methyl O -benzoyl-pyranosides has been investigated using Candida rugosa lipase in dioxane/buffer mixtures. The lipase catalysed the hydrolysis of all substrates in a regiospecific manner at C-6. The rate of reaction was dependent on pyranoside structure, reaction temperature and scale, dioxane concentration and agitation speed. Starting from their C-6 O -benzoyl precursors, the methyl 2,3,4-tri- O -benzoyl-pyranosides of ,- D -galactose, ,- D -galactose, ,- D -glucose, and methyl 2,3-di- O -benzoyl-,- D -galactopyranoside could be isolated in 85,96,% yield. In hydrolysis of methyl 2,3,4,6-tetra- O -benzoyl-,- D -glucopyranoside and methyl 2,3,4,6-tetra- O -benzoyl-,- D -galactopyranoside substrate inhibition were observed, which in part could be overcome by increasing the reaction volume. Methyl 2,3,4,6-tetra- O -benzoyl-,- D -glucopyranoside and methyl 2,3,4,6-tetra- O -benzoyl-,- D -mannopyranoside were poor substrates for Candida rugosa lipase and low degree of conversion towards products were obtained under all conditions. No acyl migration was detected in any of the products.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Determination of thiol compounds by automated headspace solid-phase microextraction with in-fiber derivatizationFLAVOUR AND FRAGRANCE JOURNAL, Issue 3 2006Qing Wang Abstract In this article, headspace solid-phase microextraction (HS-SPME) analysis of thiol compounds with both solid and aqueous samples was investigated using N -phenylmaleimide as an in-fiber derivatization reagent. The derivatives were analyzed using GC-MS. The HS-SPME method was executed on an automatic sampler and optimized by studying a variety of factors such as the selection of the fiber, extraction time, temperature, agitation speed, etc. Method validation was carried out by spiking known amounts of thiol compounds into the sample and calculating the concentration by standard addition. The relative standard deviations (RSD) for the majority of the thiols were less than 10%. The developed method resulted in a limit of detection (LOD) in the low microgram per liter for most of the thiols analyzed, which was about one order of magnitude lower than the HS-SPME without derivatization. Finally, the overall method was successfully applied for the determination of thiols in yellow onion, green onion and garlic. Copyright © 2006 John Wiley & Sons, Ltd. [source] Kinetics of synthesis of bis-(benzoxazolyl-2-methyl) sulfide under phase-transfer catalysis conditionsINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 5 2009Zuo-Xiang Zeng Kinetics of synthesis of bis-(benzoxazolyl-2-methyl) sulfide (BBMS) is investigated under phase-transfer catalysis conditions. Thus, the reaction of 2-chloromethylbenzoxazole and sodium sulfide is carried out in a two-phase (organic/water) medium, and quaternary ammonium salt and quaternary phosphonium salt are used as phase-transfer catalyst (PTC) in the reaction. The conversion of 2-chloromethylbenzoxazole is dramatically enhanced by adding a small quantity of PTC and is also greatly affected by the reaction conditions. The effects of various reaction variables on the kinetics are investigated, including the amount of catalyst, the temperature, the kinds of catalysts, the kinds of solvents, and the agitation speed. An interfacial reaction mechanism is proposed to explain the characteristics of the reaction. A pseudo-first-order rate model is established to describe the relationship between the fractional conversion and the reaction time. The kinetics data demonstrate that the model is suitable to the reaction of synthesis of BBMS. © 2009 Wiley Periodicals, Inc. Int J Chem Kinet 41: 296,302, 2009 [source] Fabrication by three-phase emulsification of pellicular adsorbents customised for liquid fluidised bed adsorption of bioproductsJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 11 2003Mohsen Jahanshahi Abstract A novel dense pellicular adsorbent, custom-designed for liquid fluidised bed adsorption of protein bioproducts, has been fabricated by coating zirconia,silica particles with agarose gel in a three-phase emulsification process. A slurry feedstock comprising solid zirconia,silica particles (120 µm average diameter) suspended in an aqueous solution of agarose was emulsified in an oil,surfactant mixture in a stirred vessel to yield composite droplets. These were subsequently stabilised by cooling to form spherical pellicular particles characterised by a porous, pellicular coat cast upon a solid core. The impact of agitation speed, surfactant concentration, oil viscosity and slurry composition upon the pellicle depth and overall particle diameter was investigated. Pellicle depth decreased with increasing impeller speed and decreased oil viscosity, whilst increased slurry viscosity enhanced that parameter. Initial increases from low concentrations of Span 80 surfactant (0.1% w/v oil) reduced the depth of the agarose pellicle, but the highest values investigated (1.5% w/v oil) promoted particle aggregation. The fluidisation behaviour of particles fabricated under various conditions was characterised by the measurement of expansion coefficients and axial dispersion coefficients for the liquid phase when operated in a standard fluidised bed contactor. Both parameters were found to be comparable or superior to those reported for conventional, composite fluidised bed adsorbents. The controlled coating of porous agarose upon a solid core to yield specific pellicular geometries is discussed in the context of the fabrication of adsorbents customised for the recovery of a variety of bioproducts (macromolecules, nanoparticulates) from complex particulate feedstocks (whole broths, cell disruptates and unclarified bio-extracts). Given the agreement between the size of the pellicular particles and the trends expected from theory, the large-scale manufacture of such particles for customised industrial use is recommended. Copyright © 2003 Society of Chemical Industry [source] Sorption of tannic acid on zirconium pillared clayJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 1 2002P Vinod Abstract Zirconium pillared clay (PILC) was prepared using montmorillonite as the base clay. Adsorption of tannic acid (tannin) was studied by a batch equilibrium technique, as a function of adsorbate concentration, temperature, pH, agitation speed, particle size of the adsorbent and ionic strength. The process of uptake is governed by diffusion controlled first-order reversible rate kinetics. The higher uptake for the pH range 4.0,6.0 was attributed to external hydrogen bonding between phenolic-OH groups of tannin molecules and the hydrogen bonding sites on the clay. The removal of tannin by adsorption was found to be >99.0% depending on the initial concentration in the pH range of 4.0,6.0. The process involves both film and pore diffusion to different extents. The effects of solute concentration, temperature, agitation speed and particle size on the diffusion rate were investigated. Tannin uptake was found to increase with ionic strength due to the compression of diffuse double layers. The applicability of Langmuir and Freundlich isotherm models has been tested. The maximum adsorption capacity of PILC was found to be 45.8,µmol,g,1 of clay and the affinity constant is 2.9,×,10,2,dm3,µmol,1 at 30,°C. Thermodynamic parameters such as ,G,°,,H,° and ,S,° were calculated to predict the nature of adsorption. The isosteric enthalpies of adsorption were also determined and found to decrease with increasing surface coverage. Regeneration with hot water (60,°C) has been investigated for several cycles with a view to recovering the adsorbed tannin and also restoring the sorbent to its original state. Copyright © 2001 Society of Chemical Industry [source] Polymerisable Miniemulsions Using Rotor-Stator HomogenisersMACROMOLECULAR REACTION ENGINEERING, Issue 4 2008Ula El-Jaby Abstract The use of a rotor-stator mixer as a homogenisation device to make miniemulsion droplets with industrially pertinent solid contents was investigated. Methyl methacrylate/butyl acrylate (50:50 w/w ratio) miniemulsions with droplet diameters from 2 µm to 300 nm and polydispersity indices from 1.2 to 3.6 were used. Miniemulsions with three different mean droplet diameters (300, 400, 600 nm) were polymerised and the evolution of particle size was observed. When 300 nm droplets were polymerised they yielded particles of similar diameter to the original droplets, whereas particle coalescence of the growing particles with a loss of control over the particle size distribution was observed for the 400 and 600 nm droplets. The influence of costabiliser, agitation speed, solid content, colloidal protectors and surface coverage on the evolution of the droplet size and size distribution as well as on the evolution of the average particle size and its distribution were examined. It was observed that changing the above parameters had no impact on the evolution of the particle size, suggesting we have a very robust miniemulsion system. [source] Generation of high rapamycin producing strain via rational metabolic pathway-based mutagenesis and further titer improvement with fed-batch bioprocess optimizationBIOTECHNOLOGY & BIOENGINEERING, Issue 3 2010Xiangcheng Zhu Abstract Rapamycin is a triene macrolide antibiotic produced by Streptomyces hygroscopicus. Besides its wide application as an effective immunosuppressive agent, other important bioactivities have made rapamycin a potential drug lead for novel pharmaceutical development. However, the low titer of rapamycin in the original producer strain limits further industrialization efforts and restricts its use for other applications. Predicated on knowledge of the metabolic pathways related to rapamycin biosynthesis in S. hygroscopicus, we have rationally designed approaches to generate a rapamycin high producer strain of S. hygroscopicus HD-04-S. These have included alleviation of glucose repression, improved tolerance towards lysine and shikimic acid, and auxotrophy of tryptophan and phenylalanine through the application of stepwise UV mutagenesis. The resultant strain produced rapamycin at 450,mg/L in the shake flask scale. These fermentations were further scaled up in 120 and 20,000,L fermentors, respectively, at the pilot plant. Selected fermentation factors including agitation speed, pH, and on-line supplementation were systematically evaluated. A fed-batch strategy was established to maximize rapamycin production. With these efforts, an optimized fermentation process in the larger scale fermentor was developed. The final titer of rapamycin was 812,mg/L in the 120,L fermentor and 783,mg/L in the 20,000,L fermentor. This work highlights a high rapamycin producing strain derived by mutagenesis and subsequent screening, fermentation optimization of which has now made it feasible to produce rapamycin on an industrial scale by fermentation. The strategies developed here should also be applicable to titer improvement of other important microbial natural products on an industrial scale. Biotechnol. Bioeng. 2010;107: 506,515. © 2010 Wiley Periodicals, Inc. [source] Optimization of Rosmarinic Acid Production by Lavandula vera MM Plant Cell Suspension in a Laboratory BioreactorBIOTECHNOLOGY PROGRESS, Issue 2 2005Atanas I. Pavlov The all-round effect of dissolved oxygen concentration, agitation speed, and temperature on the rosmarinic acid production by Lavandula veraMM cell suspension was studied in a 3-L laboratory bioreactor by means of the modified Simplex method. Polynomial regression models were elaborated for description of the process of rosmarinic acid production (Y) in the bioreactor as a consequence of the variation of the dissolved oxygen (X1) concentration between 10% and 50%; agitation (X2) between 100 and 400 rpm; and temperature (X3) between 22 and 30 °C. The optimization made it possible to establish the optimal conditions for the biosynthesis of rosmarinic acid by L. veraMM: dissolved oxygen (X1*), 50% of air saturation; agitation (X2*), 400 rpm; and temperature (X3*), 29.9 °C, where maximal yield (Ymax) of 3489.4 mg/L of rosmarinic acid was achieved (2 times higher compared with the shake-flasks cultivation). [source] Optimization of Cyclodextrin Glycosyltransferase Production from KlebsiellapneumoniaeAS-22 in Batch, Fed-Batch, and Continuous CulturesBIOTECHNOLOGY PROGRESS, Issue 6 2003Bharat N. Gawande Production of a novel cyclodextrin glycosyltransferase (CGTase) from Klebsiella pneumoniaeAS-22 strain, which converts starch predominantly to ,-CD at high conversion yields, in batch, fed-batch, and continuous cultures, is presented. In batch fermentations, optimization of different operating parameters such as temperature, pH, agitation speed, and carbon-source concentration resulted in more than 6-fold increase in CGTase activity. The enzyme production was further improved by two fed-batch approaches. First, using glucose-based feed to increase cell density, followed by starch-based feed to induce enzyme production, resulted in high cell density of 76 g dry cell weight/L, although the CGTase production was low. Using the second approach of a single dextrin-based feed, 20-fold higher CGTase was produced compared to that in batch fermentations with media containing tapioca starch. In continuous operation, more than 8-fold increase in volumetric CGTase productivity was obtained using dextrin-based media compared to that in batch culture using starch-based media. [source] Combined Effect of Agitation/Aeration and Fed-Batch Strategy on Ubiquin- one-10 Production by Pseudomonas diminutaCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 6 2010Mahesh V. Bule Abstract The effects of aeration rate and agitation speed on ubiquinone-10 (CoQ10) submerged fermentation in a stirred-tank reactor using Pseudomonas diminuta NCIM 2865 were investigated. CoQ10 production, biomass formation, glycerol utilization, and volumetric mass transfer coefficient (kLa) were affected by both aeration and agitation. An agitation speed of 400,rpm and aeration rate of 0.5,vvm supported the maximum production (38.56,mg,L,1) of CoQ10 during batch fermentation. The fermentation run supporting maximum production had an kLa of 27.07,h,1 with the highest specific productivity and CoQ10 yield of 0.064,mg,g,1h,1 and 0.96,mg,g,1 glycerol, respectively. Fermentation kinetics performed under optimum aeration and agitation showed the growth-associated constant (a,=,5.067,mg,g,1) to be higher than the nongrowth-associated constant (,,=,0.0242,mg,g,1h,1). These results were successfully utilized for the development of fed-batch fermentation, which increased the CoQ10 production from 38.56,mg,L,1 to 42.85,mg,L,1. [source] | ||||||||||||||||