Calcium Alginate Spheres Research Articles

Alginate Spheres: Influence of Agar and Xanthan Gum Incorporation on Membrane Stability and Permeability

Calcium alginate spheres with a volume of about 5 mL can be used for important purposes. Those that incorporate oolong tea give, in addition to the recreational aspect, the possibility of drinking small quantities of this tea, because oolong tea can be used as a compound with antioxidant properties. This incorporation can be achieved by reverse spherification (5 mL). Six types of spheres have been made, all of them with calcium alginate and the presence or absence of agar-agar and xanthan gum—XG—in two concentrations. The weight loss of the spheres, the release of bioactive compounds over time (a total of 48 h), the surface (internal and external) of the membranes, and the physical characteristics of these membranes have been analyzed. The data obtained indicate that the presence of XG prevents the formation of precipitates inside the spheres and slows down weight loss. It also provides opacity to the spheres. However, the incorporation of agar-agar does not have a significant influence on the different parameters analyzed. The release of catechins reaches a maximum of 80% of what could be achieved under ideal conditions, and it reaches 90% in the first 3 h. The incorporation of XG increases the shelf life of the spheres, slows down the release of chelate, and decreases weight loss over time, allowing for a new perspective on the spherification process.

Calcium alginate-immobilized β-glucosidase from Moniliophthora perniciosa: characterization and sugarcane bagasse hydrolysis

The utilization of lignocellulosic materials for second-generation ethanol production via enzymatic catalysts is primarily hindered by enzyme cost. Enzymatic immobilization emerges as a viable solution, enabling enzyme reuse. This study investigated the immobilization of an enzymatic extract obtained from Moniliophthora perniciosa fermentation in calcium alginate spheres using the direct trapping method. Initial tests assessed β-glucosidase activity, showing that a higher concentration of calcium chloride (1 M) alongside larger diameter spheres yielded improved results. The immobilized enzyme was reused for up to 17 cycles without significant loss of activity. The percentage of reducing sugars after 48-h hydrolysis with the supplemented enzymatic extract was 226%, doubling the value achieved with only the free enzymatic extract. The immobilized enzyme retained 50% of its initial activity after 1 h at 80 °C, demonstrating higher activity at pH 6 and 60 °C. These findings suggest that this immobilization technique is simple, economically viable, and effective for the hydrolysis of pretreated sugarcane bagasse.

Remote Positioning of Spherical Alginate Ferrogels in a Fluid Flow by a Magnetic Field: Experimental and Computer Simulation.

This work belongs to the development of mechanical force-responsive drug delivery systems based on remote stimulation by an external magnetic field at the first stage, assisting the positioning of a ferrogel-based targeted delivery platform in a fluid flow. Magnetically active biopolymer beads were considered a prototype implant for the needs of replacement therapy and regenerative medicine. Spherical calcium alginate ferrogels (FGs)~2.4 mm in diameter, filled with a 12.6% weight fraction of magnetite particles of 200-300 nm in diameter, were synthesized. A detailed characterization of the physicochemical and magnetic properties of FGs was carried out, as were direct measurements of the field dependence of the attractive force for FG-beads. The hydrodynamic effects of the positioning of FG-beads in a fluid flow by a magnetic field were studied experimentally in a model vessel with a fluid stream. Experimental results were compared with the results of mathematical and computer modeling, showing reasonable agreement. The contributions of the hydrodynamic and magnetic forces acting on the FG-bead in a fluid flow were discussed. Obtained forces for a single ferrogel implant were as high as 0 to 10-4 N for the external field range of 0 to 35 kA/m, perfectly in the range of mechanical force stimuli in biological systems.

Cr(VI) removal from groundwater by calcium alginate coating microscale zero‐valent iron and activated carbon: Batch and column tests

AbstractAlthough most of the studies focus on the nanoscale zero‐valent iron (nZVI), it still ineffective when comes to in situ utilization due to its intrinsic drawbacks such as rapid aggregation, biotoxicity, high cost, complex preparation process, and so forth. With advantages of lower health risk, lower cost, and simpler fabricate method, microscale zero‐valent iron (mZVI) shows more attractiveness for groundwater remediation than nZVI if its main problem, passivation, can be alleviated. In order to overcome the passivation of mZVI, (mZVI+AC)/CA was produced by encapsulating mZVI and activated carbon (AC) in spherical calcium alginate (CA) matrix in this study. The method effectively solved the passivation of mZVI and showed great long‐effective removal of Cr(VI). The Cr(VI) removal efficiency of (mZVI+AC)/CA could maintain 1.6–2.69 times as much as that of pure mZVI for 0–1500 pore volumes. The maximum Cr(VI) removal capacity reached 100.47 mg/g, which exceeded most of mZVI‐based materials and even some nZVI‐based materials. In addition, mechanism of Cr(VI) removal was revealed by X‐ray diffraction and X‐ray photo‐electron spectroscopy. The results showed that chemisorption, physisorption, reduction, oxidation, and precipitation were involved in the process. Pseudo‐second order model and Freundlich isotherm model were best fitted in kinetics and isotherm experiments, respectively.

Validation of CFD-DEM simulation of a liquid–solid fluidized bed by dynamic analysis of time series

Liquid–solid fluidized beds (LSFB) modeling validation is crucial for establishing design rules and monitoring tools. However, it generally relies on comparing global variables, which overlook dynamic features that influence reaction outputs. This work aims to implement time series analysis tools to compare Radioactive Particle Tracking data with a simulation consisting of Computational Fluid Dynamics coupled with Discrete-Element Method. Experiments have been performed in a pilot-scale LSFB of calcium alginate spheres fluidized with a calcium chloride solution. The Diks’ test indicates that the simulation can capture the LSFB behavior. It also allows diagnosing flow regime transitions from the simulation. Trends of solid dispersion coefficients and mixing times predicted by the simulation are in good agreement with the experiments.

Comparison of the Fluidized State Stability from Radioactive Particle Tracking Results

Currently, various industrial processes are carried out in fluidized bed reactors. Knowing its internal dynamics is fundamental for the intensification of these processes. This work assesses the motion of fluidized calcium alginate spheres under the influence of an upward fluid flow within a 1.2 m high and 0.1 m inner diameter acrylic column. The liquid–solid fluidized bed was compared with a gas–liquid–solid fluidized bed operation mode in terms of mixing behavior. The radioactive particle tracking technique is a proper methodology to study the internal dynamics of these kinds of equipment. Data gathered were analyzed with Shannon entropy as a dynamic mixing measure. Mixing times were found to be between 1 and 2.5 seconds for both fluidization modes. The liquid–solid fluidized bed presents a rather smooth mixing time profile along the column. On the other hand, the gas–liquid–solid fluidized bed showed high sensitivity of entropy production with height, reaching a sharp tendency break at the second quartile of the column. The Glansdorff–Prigogine stability measure can accurately capture flow regime transitions of the gas–liquid–solid fluidized bed, allowing it to be used to construct reliable operative windows for fluidization equipment.

Hydrolysis of whey lactose: Kluyveromyces lactis β-galactosidase immobilisation and integrated process hydrolysis-ultrafiltration

The β-galactosidase (β-gal) from Kluyveromyces lactis was immobilised in calcium alginate spheres and a new integrated process was investigated using hydrolysis and ultrafiltration of whey. Samples of bovine, caprine, and bubaline whey were treated. The effects of pH, temperature, storage and thermal stability were studied for the free and immobilised β-gal. For both free and immobilised enzyme, optimum pH and temperature was found to be 7.0 and 35 °C, respectively. Michaelis–Menten constant (Km) was 2.86 and 4.37 mm for the free and immobilised enzyme, respectively. Reuse, storage, and thermal stability of the β-gal were increased by immobilisation. The integrated hydrolysis-UF resulted in similar values of protein concentration and permeate flux to that obtained by independent UF. The proposed hydrolysis-UF process was demonstrated to be efficient in reducing the operational time by combining two operations in addition to the enzyme reuse.

Swelling Behavior and Drug Release of Polymer Coated Nano Iron Oxide Embedded Hydroxyapatite

Spherical calcium-alginate gel beads containing HAIO, iron oxide (IO) nanoparticles embedded on hydroxapatite (HA), were prepared along with and poly (N-isopropylacrylamide) (PNIPAAM) or chitosan. These spheres, HAIO, HAIO-PNIPAAM and HAIO-chitosan spheres, were used as carriers of 5-fluorouracil (5-FU), one of the drugs for cancer chemical therapy, and the 5-FU release behavior in PBS solution was investigated at ambient and elevated temperatures using U-V spectrometry. The amount of the released 5-FU from the HAIO spheres was somewhat higher than that from HAIO-PNIPAAM and HAIO-chitosan spheres at ambient temperature. At elevated temperature, HAIO spheres showed an increase in quantity of released 5-FU. The amount of released 5-FU from HAIO-PNIPAAM spheres was almost the same, and that from HAIO-chitosan spheres was reduced compared to those at ambient temperature. These spheres, HAIO, HAIO-PNIPAAM and HAIO-chitosan spheres, show the similar swelling properties at elevated temperature. However, the combinations of Ca-alginate - PNIPAAM or Ca-alginate - chitosan may produce the different structures, which are core-shell network for HAIO-PNIPAAM spheres and or a polyelectrolyte complex for HAIO-chitosan spheres, leading to a different release behavior of 5-FU.

Effect of bacterial alginate on growth of mesenchymal stem cells

Capsular alginate was synthesized using bacteria Azotobacter agile 12 in order to test its potential for use in biotechnology and tissue engineering. Capsular bacterial alginate was isolated and purified using EDTA treatment and dialysis. Calcium alginate spheres were produced and their effect on growth of mesenchymal stem cells was studied. Bacterial alginate shows significantly lower cytotoxicity than commercial alginate isolated from algae.

Investigation of kinetics of supercritical drying of alginate alcogel particles

Spherical calcium alginate gel particles were synthesized by dripping method. The effects of temperature, pressure, particle size and CO2 flow rate on kinetics of supercritical drying of alginate gel particles in a packed bed were investigated. Increase in CO2 flow rate, increase in temperature and decrease in particle size increased the drying rate and decreased the drying time. A mathematical model based on (i) the diffusion of the solvent inside the pores of gel particles, (ii) external mass transfer of the solvent from the surface of the gel particles into the flowing fluid stream, and (iii) convection and axial dispersion of the solvent in the flowing fluid stream was developed. A correlation for predicting external mass transfer coefficients for supercritical drying of alcogel particles was developed by fitting the model to experimental data. A good agreement between the experimental data and model results was achieved using the developed correlation.

Microfluidic synthesis of highly spherical calcium alginate hydrogels based on external gelation using an emulsion reactant

Alginate-based hydrogels are widely used in the biomedical and chemical fields, and their size and shape are significant to their applications like drug delivery and cell encapsulation. Here, we report a microfluidic external gelation process using an on-chip calcium chloride (CaCl2) emulsion reactant for producing highly spherical calcium alginate (Ca-alginate) hydrogel particles. The microfluidic channels were two serial cross-junctions fabricated on quartz glass. Monodisperse sodium alginate (Na-alginate) droplets with diameters greater or smaller than the opening (ranging from 176 μm to 225 μm) with a coefficient of variation (CV) less than 3% were successfully generated at the upstream cross-junction; they then reacted with the CaCl2 emulsion at the downstream cross-junction, forming Ca-alginate hydrogels. The effects of the fraction of the aqueous phase in the reactant CaCl2 emulsion and the flow rates of continuous and emulsion phases on the roundness of the obtained hydrogels were studied. By optimizing the parameters above, monodisperse spherical hydrogel particles were obtained with diameters ranging from 147 μm to 176 μm with CVs around 5%. The synthesis of magneto-responsive hydrogels with asymmetric Fe3O4 coatings was also demonstrated.

CFD-DEM modeling of solid motion in a water-calcium alginate fluidized column and its comparison with results from radioactive particle tracking

The motion of calcium alginate spheres in a liquid-solid fluidized bed is examined by radioactive particle tracking (RPT) and simulated by computational fluid dynamics coupled with discrete element method (CFD-DEM). Observables relevant for phenomenological models of the solid motion determined from RPT are compared with those arising from the CFD-DEM simulations. Bed expansion, solid distribution, time averaged velocity fields and axial dispersion coefficients calculated from simulations reasonably agree with the experimental values. The influence of the liquid inlet distribution on simulations results is examined. A non-negligible effect is observed on the predicted velocity profiles, solid distribution and dispersion coefficients, mainly in the entrance region. Uniform liquid distribution at the entrance generally predicts a less steeped profile. When the liquid inlet distribution is parameterized considering the geometry of the experimental distributor, the fitting of the solid mean axial velocity and solid distribution radial profiles, judged from a sum of squares of relative errors, improves in 90% and 80%, respectively, compared to results obtained when considering a uniform liquid distribution at the entrance.

Alginate clay hybrid composite adsorbents for the reclamation of industrial lean methyldiethanolamine solutions

Abstract Alginate based clay hybrid composites were used as adsorbents for the removal of total organic acid anions (TOA) as heat stable salt (HSS) and heavy metal ions (chromium and iron) from industrial lean methyldiethanolamine (MDEA, 50 wt%) solvents. Spherical calcium alginate based hybrid (CAH) composites were prepared using three different filler clays such as sepiolite, montmorillonite and bentonite. To overcome the inherent iron leaching problem associated with clay minerals, an appropriate clay treatment method was utilized before preparing the hydrogel composite. The structure of the clay (before and after modification) and composites was characterized by XRD, whereas the sorption mechanism of the CAH hydrogel composites was conferred in combination with the results obtained from SEM, EDX and FTIR analyses. The effect of quantitative contributions of polymer, bead size, agitation speed, cross linker concentration, reaction time and filler weight% were studied using batch adsorption. The initial experiments confirmed that all the hybrid composites could superiorly separate HSS and heavy metal ions from lean MDEA solvents. 2.0 wt% clay containing composite hydrogels prepared by using 1 mm dropper in a CaCl2 solution of 1.5 M was found to have highest adsorption capacity. Thus, calcium alginate hybrid (CAH) composites showed efficient adsorption capacity for removing all the contaminants present in lean MDEA.

Tailor-made biocatalysts based on scarcely studied acidic horseradish peroxidase for biodegradation of reactive dyes.

Peroxidases (EC 1.11.1.7) have enormous biotechnological applications. Usage of more abundant, basic isoforms of peroxidases in diagnostic kits and/or in immunochemistry has led to under exploitation and disregard of horseradish peroxidase (HRP) acidic isoforms. Therefore, acidic horseradish peroxidase (HRP-A) isoenzyme was used for the preparation of a biocatalyst with improved ability in dye decolorization. Ten biocatalysts were prepared by covalent binding of enzyme to chitosan and alginate, adsorption followed by cross-linking on inorganic support (aluminum oxide), and encapsulation in spherical calcium alginate beads via polyethylene glycol. Model dyes of 50 to 175mgl-1 were removed by the biocatalysts. Among the tested biocatalysts, the three with the highest specific activity and biodegradation rate were further studied (Chitosan-HRP, Al-Gel-HRP and Al-HRP-Gel). The impact of hydrogen peroxide concentration on dye decolorization was examined on the Chitosan-HRP biocatalyst, since the HRP is susceptible to inhibition/inactivation by high H2O2. On the other hand, H2O2 is needed as a co-substrate for the HRP, and the H2O2/dye ratio can greatly influence decolorization efficiency. Concentrations of H2O2 ranging from 0.22 to 4.4mM showed no difference in terms of impact on the biocatalyst decolorization efficiency. The high decolorization efficiency of the biocatalysts was validated by the removal of 25 and 100mgl-1 anthraquinone (Remazol Brilliant Blue R (RBBR)), triphenylmethane (Coomassie Brilliant Blue (CBB)), acridine (Acridine Orange (AO)), and formazan metal complex dye (Reactive Blue 52 (RB52)). After the seven consecutive decolorization cycles, the decolorization was still 53, 78, and 67% of the initial dye for the Al-HRP-Gel, Al-Gel-HRP, and Chitosan-HRP immobilizate, respectively. The results obtained showed potential of otherwise neglected acidic HRP isoforms as a cost-effective biocatalyst with significant potential in wastewater dyestuff treatment.

Kluyveromyces lactis β-galactosidase immobilization in calcium alginate spheres and gelatin for hydrolysis of cheese whey lactose

ABSTRACT: One of the greatest challenges for dairy industries is the correct destination of all the whey generated during cheese making, considering its high impact, the large volume created, and its technological potential. Enzymatic hydrolysis of cheese whey lactose is a biotechnological alternative. However, one of the limiting factors of its use is the relatively high cost of the enzymes, which could be lowered with the immobilization of these biocatalysts. Considering this context, the objective of this research was to evaluate the commercial Kluyveromyces lactis β-galactosidase enzyme immobilized in calcium alginate spheres and gelatin, using glutaraldehyde and concanavalin A (ConA) as modifying agents in the hydrolysis of cheese whey lactose process. Results have shown that the enzyme encapsulation complexed with ConA in alginate-gelatin spheres, without glutaraldehyde in the immobilization support, has significantly increased the hydrolysis of lactose rate, achieving a maximum conversion of 72%.

Viability of Lactobacillus acidophilus Immobilized in Calcium Alginate Spheres and Submitted to Different Conditions of Stress

Viability of Lactobacillus acidophilus Immobilized in Calcium Alginate Spheres and Submitted to Different Conditions of Stress

Kinetic and morphology study of alginate-vineyard pruning waste biocomposite vs. non modified vineyard pruning waste for dye removal

In this work a comparative bioadsorption study between a biocomposite consisting of hydrolysed vineyard pruning waste entrapped in calcium alginate spheres and non entrapped vineyard residue was carried out. Results have demonstrated that the biocomposite based on lignocellulose-calcium alginate spheres removed 77.3% of dyes, while non entrapped lignocellulose eliminated only removed 27.8% of colour compounds. The experimental data were fitted to several kinetic models (pseudo-first order, pseudo-second order, Chien–Clayton model, intraparticle diffusion model and Bangham model); being pseudo-second order the kinetic model that better described the adsorption of dyes onto both bioadsorbents. In addition, a morphological study (roughness and shape) of alginate-vineyard biocomposite was established under extreme conditions, observing significant differences between hydrated and dehydrated alginate-vineyard biocomposite. The techniques used to carry out this morphological study consisted of scanning electron microscopy (SEM), perfilometry and 3D surface analysis.

Alginate droplets pre-crosslinked in microchannels to prepare monodispersed spherical microgels

Abstract Monodispersed spherical calcium alginate microgels (denoted as Ca-ALG) with uniform and controllable size were prepared by using a microfluidics technique. Herein, an aqueous solution of sodium alginate (denoted as Na-ALG) was used as a dispersed phase, and the liquid paraffin containing CaCl 2 nanoparticles formed in situ was used as a continuous phase. Na-ALG droplets were first pre-crosslinked by CaCl 2 diffused from the oil phase in the microchannel, and then crosslinked completely in the collection bath containing an aqueous solution of CaCl 2 . In comparison with conventional external crosslinking, this method can avoid deformation of microgels which usually occurs in the process of external crosslinking. Due to the pre-crosslinking of Na-ALG droplets in the microchannel, the spherical morphology of the microgels could not be affected by the preparation conditions, such as types of microfluidic devices, flow rate ratios of the continuous phase and dispersed phase, size of the droplets, collection height and so on. In addition, the size of the spherical Ca-ALG microgels can be well controlled from 40 to 700 μm in diameter by changing the dimension of the microchannels and the flow rate ratios of the dispersed phase and continuous phase. Furthermore, such spherical Ca-ALG microgels can improve their movement and packing state in a microchannel, which is beneficial for their use as embolic materials for interventional therapy.

Biosorption of Cr(VI) by Calcium Alginate-Encapsulated Enterobacter aerogenes T2, in a Semi-Batch Plug Flow Process

Carcinogenic heavy metal chromium, in its hexavalent form Cr(VI) is spuriously used in various industrial operations because of its hardness and stability. Due to lack of proper remediation processes, effluents contain Cr(VI) in large excess of WHO’s statutory limit of 50 μg l−1. In this study, a biosorption-based remediation strategy is proposed for the remediation of Cr(VI) from contaminated samples. The novel bacterial strain Enterobacter aerogenes T2 (GU265554, NII 1111) was isolated from Cr(VI)-contaminated tannery effluent and used for bioremediation studies. The cell-free extract (CFE) was prepared and encapsulated in spherical calcium alginate biopolymeric beads. A semi-batch plug-flow-packed bed made of these beads was used for biosorption of Cr(VI). A remediation rate of 932 mg Cr(VI) m−3 water per day with a sorption efficiency of 93.2 % was achieved. The method exhibited the best results when compared to those reported in the literature. Various isotherm models of adsorption such as Langmuir, Freundlich, and Dubinin-Radushkevich (D-R) were studied. The results predicted adsorption in a multi-layered fashion via physisorption. The developed technology could be considered as green since no synthetic chemical was used for sorption of Cr(VI).

Whole cells in enantioselective reduction of benzyl acetoacetate.

The β-ketoester benzyl acetoacetate was enantioselectively reduced to benzyl (S)-3-hydroxybutanoate by seven microorganism species. The best result using free cells was obtained with the yeast Hansenula sp., which furnished 97% ee and 85% of conversion within 24 h. After immobilization in calcium alginate spheres, K.marxianus showed to be more stable after 2 cycles of reaction.