多通道微胶囊制备系统规模化制备海藻酸钙微胶珠

利用自制多通道强制电场微胶囊制备系统制备海藻酸钙微胶珠,分析了微胶囊制备系统中电极电场分布规律,考察了进料气压、脉冲电压、脉冲频率、脉冲宽度、辅助电压等系统调节参数对微胶珠制备过程的影响,发现制备过程中微胶珠粒径大小与产率主要由进料气压决定,而微胶珠的分散性则是由多个因素共同作用的结果。通过优化条件制备的微胶珠分散系数较小（CV<20%）,球形度良好,表面光洁,并且产率是传统静电法的20~40倍,使海藻酸钙微胶珠大规模制备成为可能。     

Preparation of interpenetrating polymer network gel beads for dye absorption

Preparation of interpenetrating polymer network (IPN) gel beads for dye absorption was carried out by using simultaneous crosslinking method. First, sodium alginate (SA), 3‐(methacrylamido) propyl trimethyl ammonium chloride (MAPTAC), and/or acrylamide (AM), K₂S₂O₈, and N,N′‐methylenebisacrylamide (MBAM) were mixed in aqueous solution. The beads were prepared using K₂S₂O₈ and MBAM as the initiator and crosslinking agent, respectively. Then, the solution was dropped into CaCl₂ solution mixed with N,N,N′,N′‐tetramethylethylenediamine (TMEDA). The former was used as the crosslinking agent of alginate and the latter was used as the accelerator for the polymerization of monomer in the alginate solution. The gel bead composed of only alginate was also prepared to compare the properties with IPN gel bead. The components in IPN gel bead were examined by FTIR analysis. The factors effecting the particle size of alginate and IPN gel beads were investigated. In alginate gel bead, the concentration of solution affected the particle size, whereas type of monomer affected the particle size of IPN gel bead. The IPN gel bead had smooth surface (from SEM results), different from the alginate bead. Alginate content caused the swelling behavior of dried IPN beads. Cationic dye was absorbed by crosslinked alginate gel bead. The absorption of reactive dye by IPN gel bead was a result of its cationic charge. The absorption density of IPN gel beads was the reciprocal of the absorbent dosage. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1585–1591, 2006     

Alginate/carboxymethyl chitosan composite gel beads for oral drug delivery

This paper reports the synthesis of pH-sensitive gel beads derived from alginate (SA) and carboxymethyl chitosan (CMCS) for drug delivery. The composite SA/CMCS gel beads were prepared by dual ionic gelation: one ionic gelation between SA and Ca²⁺ and another one between CMCS and β-Sodium glycerophosphate (β-GP). The structure properties of hydrogel beads were characterized by SEM, IR and TG technique. The influence of the polymer composition and cross-linkers on the gel swelling property was investigated. When the concentration of CMCS and SA were 3 % and the volume ratio was 1:2, the swelling rate of gel beads crosslinked by β-GP and CaCl₂ solution can increase up to 31.2 and the swelling time can reach 10.5 h. In the drug release study, bovine serum albumin (BSA) was chosen as model drugs. The results indicated that BSA released slowly from the gel beads at pH 1.2 and the release ratio was about 10 %. At pH 7.4, the amounts of BSA released increased significantly as compared to those released at pH 1.2 and the total release time was extended to 11 h. The composite gel system demonstrates sustained release profile and pH sensitivity, which can be considered as good candidates for oral drug delivery systems.     

Evaluation of chitosan tripolyphosphate gel beads as bioadsorbents for iron in aqueous solution and in human blood in vitro

Nonimprinted and Fe³⁺ imprinted chitosan tripolyphosphate gel beads were prepared via physical gel formation. A method based on in situ crosslinking using ethylene glycol diglycidyl ether was developed to imprint the chitosan tripolyphosphate gels with Fe³⁺ ion without deteriorating the gel beads. The beads were characterized by FTIR, SEM, XRD, and DSC with respect to the chemical structure, surface morphology, crystallinity, and thermal behavior. Swelling kinetics and Fe³⁺ ion adsorption behavior from aqueous solution were studied. The Fe³⁺ imprinted and in situ crosslinked beads proved to be durable and effective adsorbents for Fe³⁺ in solution. The bead prepared by in situ crosslinking and in the presence of 10 mM template ion had an equilibrium iron adsorption capacity of 53.9 mg/g after 3-hour contact with 5 mM Fe³⁺ solution. The pros and cons of the beads as biomedical iron adsorbents were tested by evaluating their serum iron removal capacities from human blood. The preliminary tests carried out showed that Fe³⁺ imprinted beads were more effective in decreasing serum iron in human blood when compared to the nonimprinted beads. The decrease in serum iron level accompanied a parallel decrease in the hemoglobin level. The calcium level was also affected upon contact with the beads. The Fe³⁺ imprinted beads were less effective than the nonimprinted ones in decreasing the calcium level indicating selectivity towards iron containing species. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Evaporation of Distilled Water in a Fluidized Bed of Various Types of Fluidizing Particles Under Reduced Pressure

An objective of this study is to continuously obtain dispersed, dry, fine powders from a dilute suspension of heat-sensitive materials at a low temperature and high drying rate. A fluidized bed under reduced pressure was used in this study and, as a first step, only distilled water (without solid powders) was used as a sample. Drying characteristics were examined for various types of fluidizing particles. The diameter of fluidizing particle varied for inert particles (glass beads). Three kinds of hygroscopic porous particles (silica gel beads; 3A, 4B, and 5D) were also used as fluidizing particles. Under reduced pressures, the maximum drying rate was found to be higher than that at atmospheric pressure, while the bed temperature became lower with an increase in the maximum drying rate (i.e., drying at lower temperature with a higher drying rate is possible under reduced pressures. As diameter of the fluidizing particle was increased, the maximum drying rate became higher, although the amount of gas required for fluidization also increased. The maximum drying rates for silica gel beads were found to be almost equal to those of glass beads, with the exception of 3A silica gel beads (having a smaller pore diameter). The bed temperature was lower for silica gel beads compared to glass beads at the same maximum drying rate (i.e., silica gel beads (hygroscopic porous particles) are superior to glass beads (inert particles) with regard to drying at low temperatures at a high drying rate).     

Application of Plackett–Burman screening design to the modeling of grafted alginate–carrageenan beads for the immobilization of penicillin G acylase

Grafted alginate–carrageenan beads were used to immobilize the industrial enzyme penicillin G acylase (PGA). Sixteen factors were screened with the Plackett–Burman design (PBD) to test their significance on the gel beads formation and enzyme immobilization process. The results of PBD showed a wide variation of 30‐fold in the amount of immobilized penicillin G acylase (iPGA) from 11.9 to 354.16 U/g of beads; this reflected the importance of the optimizing process. Among the 16 tested factors, only 3 were proven to be significant. These factors were the enzyme buffer pH (N), enzyme soaking time (Q) with the gel beads, and enzyme concentration (P). The Pareto chart revealed that both Q and P exerted significant positive effects on the amount of iPGA, whereas N had a negative effect. We recommend further study to optimize only these three significant, distinctive enzyme factors. The PGA covalent attachment to the gel beads were proven by Fourier transform infrared spectroscopy, elemental analysis, and NaCl and reusability tests. The best gel bead formula succeeded in the immobilization of 354.16 U/g of beads and proved to be reusable 14 times, retaining 84% of the initial enzyme activity. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40295.     

pH‐sensitive uniform gel beads for DNA adsorption

Uniform gel beads 3 mm in diameter were obtained by the suspension polymerization of an amine functionalized monomer, N‐3‐(dimethyl amino)propylmethacrylamide (DMAPM). The polymerization of DMAPM in the form of uniform droplets could be achieved at room temperature in an aqueous dispersion medium by using Ca–alginate gel as the polymerization mold. In this preparation, potassium persulfate/tetramethyl ethylenediamine and sodium alginate/calcium chloride were used as the redox initiator and the stabilizer systems, respectively. The crosslinked DMAPM gel beads exhibited pH‐sensitive, reversible swelling–deswelling behavior. The uniform gel beads were also obtained by the copolymerization of DMAPM and acrylamide (AA) in the same polymerization system. Although copolymer gel beads with higher pH sensitivities were obtained with increasing feed concentration of DMAPM, the total monomer conversion decreased. Crosslinked DMAPM and DMAPM–AA copolymer gel beads were utilized as sorbents for DNA adsorption. The gel beads produced with higher DMAPM feed concentration exhibited higher equilibrium DNA adsorption capacity. The DNA equilibrium adsorption capacities up to 50 mg DNA/g dry gel could be achieved with the crosslinked DMAPM gel beads. This value was reasonably higher relative to the previously reported adsorption capacities of known sorbents. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 3154–3161, 2000     

Characterization of the structure and diffusion behavior of calcium alginate gel beads

A simple and novel method using gel shrinkage to indirectly characterize the structure of calcium alginate gel (CAG) beads during the calcium alginate gelation process was presented in this study. The effect of preparation process parameters (gelling cations, bead diameter, and alginate M _w and concentration) on the structure of the CAG bead formation process was thoroughly investigated. It was found that (a) the concentration of the Na⁺ and Ca²⁺ ion in gel bath was found to be the determining factor in the gel structure formation process by regulating the dissociation of alginate and the complexation of the calcium; (b) Na⁺ acts as a competitor with calcium and a screen in the electrostatic repulsion; (c) the effect of beads size below 700 μm on the structure of CAG beads can be neglected; and (d) the sodium alginate concentration has no significant effect on the gel formation process. Furthermore, the diffusion of bovine serum albumin (BSA) was controlled by the density of CAG bead. Consequently, a faster diffusion rate of BSA within the looser structure of beads can be observed. These results are keys to understanding the behavior and performance of beads in their utilization medium. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48923.     

Intraparticle cell growth and cell leakage in cultures of Nicotiana tabacum cells immobilized in calcium alginate gel beads

Immobilized Nicotiona tabacum cells in calcium alginate gel beads were prepared under various conditions and then were cultivated. The effects of different conditions of preparation, in relation to concentration of calcium ions (Ca²⁺), on intraparticle cell growth and cell leakage from beads were investigated experimentally. As the amount of Ca²⁺ incorporated into the beads increased, the numbers of cells leaked from the beads into the medium decreased. However, cell growth was inhibited by high Ca²⁺ concentrations in the beads. Optimal conditions existed, which prevented cell leakage without inhibiting intraparticle cell growth. The effect of adding CaCl₂ to the culture medium was also studied. The Ca²⁺, used for the alginate crosslinking, gradually leached from the beads with increasing cultivation time, such that the beads gradually became brittle and fragile. The addition of CaCl₂ was effective in preventing Ca²⁺ loss from the beads and cell leakage. © 2000 Society of Chemical Industry     

Uniform poly(isopropylacrylamide) gel beads for immobilization of α-chymotrypsin

In this study, α-chymotrypsin was immobilized via physical entrapment within large, uniformly spherical, and thermally reversible poly(N-isopropylacrylamide) [poly(NIPAM)] beads. The gel beads were prepared in an aqueous dispersion medium by using Ca-alginate gel as the polymerization mold. In this preparation, potassium persulfate/tetramethylethylenediamine and sodium-alginate/calcium chloride were used as the redox initiator and the stabilizer systems, respectively. Thermoresponsive poly(NIPAM) gel beads 3 mm in size and including α-chymotrypsin were produced by the proposed procedure. The use of an aqueous bead-forming medium did not cause significant enzyme leakage during the preparation of enzyme-gel beads. Michaelis–Menten kinetics was used to define the behaviors of enzyme-gel beads prepared with different enzyme loadings. The Lineweaver–Burk plot indicated that the enzyme-gel system had a reasonably higher K_m value relative to that of free enzyme due to the internal mass transfer resistance against the substrate diffusion. The enzyme-gel system exhibited the maximum activity at 30°C due to the thermoresponsive character of the carrier matrix. However, the maximum activity with the free enzyme was observed at 40°C. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:1127–1139, 1998     

Influence of Stirring on Incorporation of Particles during Solidification

Abstract

The critical freezing rate V_c was measured for glass beads suspended in naphthalene by using the tilt rotating zone melting technique. In horizontal operation with a large gas bubble sweeping along the interface during rotation, V_c increased dramatically with increasing tube rotation rate and decreasing mass of beads. Tilting the tube prevented the bubble from contacting the freezing interface and very stongly increased V_c . Siliconized glass beads were pushed as well as nontreated beads, both in horizontal operation with tube rotation and in vertical operation without stirring. Teflon particles were pushed to very high freezing rates in the horizontal rotating configuration. These results differ from those of Omenyi and Neumann, who predicted and observed that both Teflon and siliconized glass beads are not pushed by freezing naphthalene at any freezing rate.     

The effects of oxygen on β-lactam biosynthesis by alginate entrapped streptomyces clavuligerus

The physiology of Streptomyces clavuligerus has been studied by investigating oxygen uptake and β-lactam (clavulanic acid) production by free and alginate entrapped cells. The specific oxygen uptake rate of cells entrapped in strontium or calcium alginate was only about 35% of the rate in free cells. This reduction in oxygen uptake was due to reduced internal diffusion of oxygen; in addition calcium, barium and strontium ions could also cause oxygen uptake in free cells to be inhibited. Measurements of the deformation of individual gel beads showed that maximum hardness was reached after 15 min exposure to 0.14 mol dm^?3 Ca²⁺. Exposure of cells to Ca²⁺ for this time caused a 15% reduction in the rate of oxygen uptake. Levels of clavulanic acid produced by free cells were higher than those produced by immobilized cells; production was dependent on the degree of aeration of the cells.     

Modelling of phenol biodegradation by Candida tropicalis immobilised in alginate gel beads

Phenol‐degrading yeast Candida tropicalis were immobilised in alginate gel beads and photographed by scanning electron microscopy. Batch phenol biodegradation experiments were done in shaking flasks under varying conditions such as initial phenol concentrations and bead loadings. A mathematical model was proposed to simulate the batch phenol biodegradation process in the immobilised system, which took into account the internal and external mass transfer resistances of phenol and oxygen and the double‐substrate phenol–oxygen intrinsic kinetics. The validation of this model was done by the comparison between the model simulations and the experimental measurements of phenol concentration profiles in the main liquid phase. Moreover, the time and radius courses of phenol, oxygen, and cell concentration profiles within the alginate gel beads were reasonably predicted by the proposed model.     

高压静电法制备单分散性的海藻酸钙微胶珠

In this paper, the effect of operation parameters on the monodispersity of calcium-alginate gel beads prepared in high-voltage electrostatic field were analyzed. The parameters included the applied potential （U）, the distribution of electrostatic field, the frequency and the flow rate of solution through the capillary. Furthermore, the process is analyzed with the theory of jet break-up in electrostatic field. The result showed that the modified symmetrical electrostatic field was more advantageous in preparing the monodispersed gel beads than the traditional method. Meanwhile, gel beads with good monodispersity （CV〈20%） and stability without aggregation were produced under a range of applied potential （U）, frequency and flow rate of solution through the capillary.     

Simulation of batch and continuous reactors with co-immobilized yeast and β-galactosidase

A reaction-diffusion model was used to simulate a co-immobilized system utilizing the numerical method of orthogonal collocation. The production of ethanol from deproteinized whey using β-galactosidase co-immobilized with Saccharomyces cerevisiae in calcium alginate gel beads was chosen as a model system. Calculated concentrations of lactose, glucose, galactose and ethanol were compared with experimental data for a batch reactor and a continuous horizontal packed-bed reactor. The mathematical model has been used to analyse the influence of internal and external mass transfer for the continuous reactor. The external mass transfer was shown to be of minor importance. The introduction of baffles decreased the backmixing in the horizontal packed-bed reactor. Internal mass transfer was found to be the main cause of the reduction in the apparent reaction rate. Thus, much of the expected increase in reaction rate is diminished by mass transfer hindrance when the cell concentration is increased.     

Pd(II) ion adsorption onto emulsion gel beads in a fixed bed

We developed previously an emulsion gel adsorbent for improved metal adsorption. This study focuses on a continuous adsorption–desorption process of metal ions from a solution onto emulsion gel beads using the fixed-bed method. The monodisperse millimeter-sized emulsion gel beads, a polymeric hydrogel containing randomly distributed oil microdroplets of di-n-hexylsulfide as an extractant, were prepared using an automatic production method combining sedimentation polymerization and two-fluid atomization. The isotherms and the kinetics for Pd(II) adsorption were investigated. A continuous adsorption–desorption process was successfully demonstrated, and the breakthrough curve was successfully predicted by a mathematical analysis.     

Synthesis of β-SiAlON: A combined method using sol–gel and SHS processes

β-SiAlON has been prepared by a SHS reaction performed under high nitrogen pressure on a compacted mixture of silicon and mullite. In order to optimise this reaction, the solid mixture was prepared from a liquid solution in which the mullite (2SiO₂-3Al₂O₃) was formed by a sol–gel process. The SHS samples were characterized by using Scanning Electron Microscopy (SEM) and X-ray diffraction. A Rietveld refinement performed on the recorded diffractograms revealed a very high formation rate of β-SiAlON (more than 80 wt%) when the reaction was carried out under low nitrogen pressure. From the whole of our results, a mechanism of β-SiAlON formation has been suggested.     

Improvement of Permeability of Poly(vinyl alcohol) Hydrogel by Using Poly(ethylene glycol) as Porogen

The porous structure of PVA hydrogel achieved with varying content and varying molecular weight of PEG was investigated. It was found that with increasing content or molecular weight of PEG, the diffusion coefficient D _e and UV transmission of ink solution increased, indicating that the permeability and mass transfer capability of the gel beads were enhanced. The swelling rate constant k and equilibrium swelling rate of the gel were significantly improved by addition of PEG, and many pores formed inside the gel to provide channels for microbial metabolites. With increasing molecular weight of PEG, the size of pores became increasingly large.     

Optimization of pullulan production using Ca‐alginate‐immobilized Aureobasidium pullulans by response surface methodology

BACKGROUND: The production of pullulan from synthetic medium by Aureobasidium pullulans P56 immobilized in Ca‐alginate beads was investigated using batch and repeated batch fermentation systems. RESULTS: The highest pullulan concentration (19.52 ± 0.37 g dm^?3) was obtained with 2.0‐2.4 mm beads prepared from 2% sodium alginate solution. Pullulan production was mainly accomplished by immobilized fungal cells since leaked cells in the fermentation medium comprised 17.4% of the total fungal population at the end of fermentation. The pullulan proportion was 84.5% of the total polysaccharide in the fermentation medium. Response surface methodology was used to investigate the effects of three fermentation parameters (initial pH, agitation speed and incubation time) on the concentration of pullulan. Results of the statistical analysis showed that the fit of the model was good in all cases. The maximum pullulan concentration of 21.07 ± 0.48 g dm^?3 was obtained at the optimum concentrations of process variables (pH 7.31, agitation speed 191.5 rpm, incubation time 101.2 h). The gel beads produced pullulan under the optimized conditions for six consecutive batch fermentations without marked activity loss and deformation. CONCLUSION: The results of this study suggest that the immobilization of A. pullulans cells in Ca‐alginate gel beads is suitable for batch and repeated batch production of pullulan. Copyright © 2007 Society of Chemical Industry