Alginate Beads Containing Lactase: Stability and Microstructure

Immobilization of α-amylase in calcium alginate-gum odina (CA-GO) beads: An easily recoverable and reusable support

A natural polysacharide, gum odina was collected from Odina wodier tree and purified. Purified gum odina was used with sodium alginate for immobilization of α-amylase. Calcium alginate-gum odina (CA-GO) beads were prepared by ionotropic gelation method to find the improvement of immobilization efficiency and reusability of α-amylase over calcium alginate (CA) beads. XRD, SEM, FTIR, beads diameter, enzyme leaching from beads, moisture content, total soluble matter and swelling study have been carried out to understand the physical morphology and mechanism of immobilization of enzyme in beads matrix. It has been observed that if the polymer ratio changes (keeping enzyme conc. & calcium Chloride conc. constant) then the size and shape of the beads will vary and at a particular range of polymer ratio, the optimal beads forms. At a certain conc.(4%w/v of SA and 1%w/v GO), the immobilization efficiency of CA-GO and CA beads were 92.71 ± 0.85 % (w/w) and 89.19 ± 0.35 %(w/w) respectively. After 8th time use, the CA-GO beads remain (~4 fold) more active than that of CA beads. The FTIR confirms that GO does not interfere with α-Amylase and alginate. Here, it can be concluded that CA-GO beads show better efficiency in respect to immobilization, reusability than CA beads only.

Stability Studies, Biodegradation Tests, and Mechanical Properties of Sodium Alginate and Gellan Gum Beads Containing Surfactant

The excessive presence of single-use plastics is rapidly degrading our natural environment on a global scale due to their inherent resistance to decomposition. Wet wipes used for personal or household purposes contribute significantly to the accumulation of plastic waste. One potential solution to address this problem involves developing eco-friendly materials that possess the ability to degrade naturally while retaining their washing capabilities. For this purpose, the beads from sodium alginate, gellan gum, and a mixture of these natural polymers containing surfactant were produced using the ionotropic gelation method. Stability studies of the beads by observing their appearance and diameter were performed after incubation in solutions of different pH values. The images showed that macroparticles were reduced in size in an acidic medium and swelled in solution of pH-neutral phosphate-buffered saline. Moreover, all the beads first swelled and then degraded in alkaline conditions. The beads based on gellan gum and combining both polymers were the least sensitive to pH changes. The compression tests revealed that the stiffness of all macroparticles decreased with the increasing pH of the solutions in which they were immersed. The studied beads were more rigid in an acidic solution than in alkaline conditions. The biodegradation of macroparticles was assessed using a respirometric method in soil and seawater. It is important to note that the macroparticles degraded more rapidly in soil than in seawater.

Polymer/Enzyme Composite Materials—Versatile Catalysts with Multiple Applications

A significant interest was granted lately to enzymes, which are versatile catalysts characterized by natural origin, with high specificity and selectivity for particular substrates. Additionally, some enzymes are involved in the production of high-valuable products, such as antibiotics, while others are known for their ability to transform emerging contaminates, such as dyes and pesticides, to simpler molecules with a lower environmental impact. Nevertheless, the use of enzymes in industrial applications is limited by their reduced stability in extreme conditions and by their difficult recovery and reusability. Rationally, enzyme immobilization on organic or inorganic matrices proved to be one of the most successful innovative approaches to increase the stability of enzymatic catalysts. By the immobilization of enzymes on support materials, composite biocatalysts are obtained that pose an improved stability, preserving the enzymatic activity and some of the support material’s properties. Of high interest are the polymer/enzyme composites, which are obtained by the chemical or physical attachment of enzymes on polymer matrices. This review highlights some of the latest findings in the field of polymer/enzyme composites, classified according to the morphology of the resulting materials, following their most important applications.

Hydrogen-bonded lipase-hydrogel microspheres for esterification application

Lipase is the most widely used enzyme in industry. Due to its unique "lid" structure, lipase can only show high activity at the oil-water interface, which means that water is needed in the catalytic esterification process. However, the traditional lipase catalytic system cannot effectively control "micro-water" in the esterification environment, resulting in the high content of free water, which hinders the esterification reaction and reduces the yield. In this paper, a promising strategy of esterification catalyzed by polyacrylamide hydrogel immobilized lipase is reported. The porous polyacrylamide hydrogel microspheres (PHM) prepared by inverse emulsion polymerization are used as carrier to adsorb lipase by hydrogen bonding interaction. These hydrogel microspheres provide a "micro-water environment" for lipase in the anhydrous reaction system, and further provide an oil-water interface for "interface activation" of lipase. The obtained lipase-porous polyacrylamide hydrogel microspheres (L-PHMs) exhibit higher temperature and pH stability compared with free lipase, and the optimum enzymatic activity reach 1350 U/g (pH 6, 40 °C). L-PHMs can still remain about 49% of their original activity after 20 reuses. Furthermore, L-PHMs have been successfully applied to catalyze the synthesis of conjugated linoleic acid ethyl ester. The results suggest that this immobilization method opens up a new way for the application of lipase in ester synthesis.

New Sensor to Measure the Microencapsulated Active Compounds Released in an Aqueous Liquid Media Based in Dielectric Properties in Radiofrequency Range

In recent years, the general and scientific interest in nutrition, digestion, and what role they play in our body has increased, and there is still much work to be carried out in the field of developing sensors and techniques that are capable of identifying and quantifying the chemical species involved in these processes. Iron deficiency is the most common and widespread nutritional disorder that mainly affects the health of children and women. Iron from the diet may be available as heme or organic iron, or as non-heme or inorganic iron. The absorption of non-heme iron requires its solubilization and reduction in the ferric state to ferrous that begins in the gastric acid environment, because iron in the ferric state is very poorly absorbable. There are chemical species with reducing capacity (antioxidants) that also have the ability to reduce iron, such as ascorbic acid. This paper aims to develop a sensor for measuring the release of encapsulated active compounds, in different media, based on dielectric properties measurement in the radio frequency range. An impedance sensor able to measure the release of microencapsulated active compounds was developed. The sensor was tested with calcium alginate beads encapsulating iron ions and ascorbic acid as active compounds. The prediction and measurement potential of this sensor was improved by developing a thermodynamic model that allows obtaining kinetic parameters that will allow suitable encapsulation design for subsequent release.

High-intensity ultrasound-assisted extraction of phenolic compounds from cowpea pods and its encapsulation in hydrogels

Currently and according to the growing worldwide interest in the revaluation of agricultural by-products, the use of legumes waste presents great potential to obtain bioactive compounds. In this context, an extract rich in phenolic compounds was obtained from Vigna unguiculata (cowpea) pods by optimizing the high-intensity ultrasound conditions (10 min and 36% of amplitude) using response surface methodology. Then, the extract was encapsulated in Ca(II)-alginate beads with the addition of arabic or guar gums or cowpea isolated proteins. A complete morphological study by image analysis and microstructural evaluation by SAXS has been carried out. Results showed that beads containing alginate and alginate-guar gum have the highest loading efficiency of total phenolic compounds (47 ± 5%) and antioxidant activity (44 ± 3%). However, the coupled effect of the cowpea extract and the isolated proteins (at it higher concentration) increased the antioxidant capacity of the beads due to the contribution of the phenolic compounds and the amino acids with anti-radical activity, reaching a value of 67 ± 3 % of inhibition of ABTS.+. Finally, the microstructural analyses revealed that cowpea pod extract increased the interconnectivity of the rods due to the presence of trivalent cations, conferring versatility, and larger coordination to the network. Also, it was observed that the addition of cowpea proteins produced more interconnected bigger and fewer compacts rods than beads containing only alginate, increasing 12 and 49 % the interconnection and the size, respectively, and decreasing 10 % their compactness. This research demonstrated the use of cowpea sub-products as a source of bioactive compounds that further modulate the microstructure of the hydrogel network, and the outstanding potential for being incorporated in techno-functional foods by using Ca(II)-alginate as a carrier.

Structure-rheology relationships of composite gels: Alginate and Basil seed gum/guar gum

Structure-rheology relationship of binary composite gel (BCG) systems of alginate/guar gum and basil seed gum/guar gum at ratio 2:1 at different Ca²⁺ levels (2-10%) were evaluated. The highest value of structural strength was obtained at 2 % of Ca²⁺, which can be attributed to its stronger network as assessed by rheological experiments. Mechanical spectra of the alginate/guar gels explained pseudoplastic behavior with a highly interconnected elastic gel structure. The mechanical strength as well as other textural properties of the alginate and basil seed gum network was functions of its stoichiometry with calcium ions. Whereas alginate/guar gels showed an elongated globular denser structure as determined by SEM, the BSG/guar gels showed a rigid cubic as the pieces of a puzzle, presenting a softer and weaker gel structure. The alginate/guar gels showed less porosity without syneresis or shrinkage during storage as supported by its high elasticity and rigidity.

Freezing and drying of pink grapefruit-lycopene encapsulated in Ca(II)-alginate beads containing galactomannans

Lycopene extracted from pink grapefruit was encapsulated on Ca(II)-alginate beads with the addition of trehalose and galactomannans to improve its stability against freezing and drying. Three galactomannans of different physicochemical properties were studied since their inclusion affects both loading efficiency and release of lycopene in wet beads; however, there is no information about their performance during freezing and dehydration operations. The remaining lycopene and its stability towards isomerization were analyzed in beads subjected to continuous freezing, freezing/thawing cycles and vacuum- and freeze-drying. Isothermal crystallization studies were conducted by LF-NMR and related to beads formulation and lycopene stability. In the absence of excipients, lycopene was severely affected by all the treatments, retaining less than 20% of the original content. Alginate beads containing trehalose with guar gum protected more than 80% of the lycopene regardless of the employed freezing or drying methods. These beads concomitantly showed higher solid fraction than the other two galactomannans-containing systems, displaying guar gum ability to associate water. On the other hand, the addition of vinal gum affected lycopene stability (between 40 and 60% were recovered after treatments), even compromising the positive effect of a well-established cryoprotectant as trehalose. Thus, the addition of secondary excipients should be carefully conducted. The differences among galactomannans could be related to the substitution degree of the polymer chains, affecting the overall systems interactions. These results can contribute to excipients selection for the encapsulation of labile biomolecules in Ca(II)-alginate beads subjected to freezing and drying.