Obtaining viable Azospirillum brasilense SR80 cells encapsulated in alginate hydrogel

Significant researches aimed at the greening of agro-industrial production are focused on obtaining immobilized bacterial preparations with preserved proliferative function and metabolic activity. Herein, we investigated the possibility of bacteria of the genus Azospirillum to be immobilized in Ca-alginate beads. A. brasilense SR80 cells, encapsulated in an alginate hydrogel, were obtained using the “soft” immobilization method based on physical binding. We demonstrated the retained respiratory activity and growth ability of the bacteria during immobilization, thus confirming the advantageous prospects of alginate templates for azospirilla encapsulation.

Purification and immobilization of L-asparaginase from Citrobacter freundii EGY-NE1

L-asparaginase is used as an antileukemic drug and as a food additive to reduce the risk of acrylamide formation. New L-asparaginases are required to reduce costs and avoid clinical side effects. Citrobacter freundii EGY-NE1represents a potential source of new L-asparaginase. We purified extracellular L-asparaginase from Citrobacter freundii EGY-NE1 (through ammonium sulfate precipitation, dialysis, Sephadex-G50 and DEAE-cellulose columns) to 5.83 fold and 25.76 % recovery. The purified L-asparaginase was a low molecular weight enzyme of 19 kDa. It was optimally active at 37 ˚C, pH 8 and 40 mM asparagine. The Km and Vmax of the enzyme were 0.0179 M and 2.66 U/ml, respectively. Ca2+, Mg2+, K+ and Ba+ 2 activated the enzyme, while Na+, Zn+ 2, EDTA, azide, tartrate and HgCl2 inhibited it. The crude and purified enzymes were immobilized by encapsulation in Ca-alginate; this improved their stability and reusability. The entrapped L-asparaginases on Ca-alginate were examined by scanning electron microscope; their protein diameters ranged from 42.17 to 47.37 nm and from 46.78 to 71.97 nm for the immobilized crude and purified enzymes, respectively. Both the immobilized enzymes kept their maximal activity for 10 minutes at 40 ˚C. After the 5th cycle of repeated use, the immobilized purified and crude enzymes kept 91% and 89 % of their activities, respectively.

Influence of Sodium Alginate Concentration on Microcapsules Properties Foreseeing the Protection and Controlled Release of Bioactive Substances

To understand the abilities of Ca-alginate microcapsules and their specific applications in different fields, it is necessary to determine the physicochemical and structural properties of those formulated microcapsules. In this work, we aimed to study the effect of alginate concentration in the improvement of the encapsulation efficiency (EE) and on the release of phenolic and flavonoid substances. The relationship between the structure of the encapsulated bioactive substance and Ca-alginate network and their effect on the EE and release kinetics have been investigated. The incorporation, structure, morphology, and phase properties of all elaborated materials were characterized by UV-spectroscopy, Fourier transform infrared (ATR-FTIR), scanning electron microscope (SEM), and X-ray diffraction (DRX). The results indicate that increasing the polymer concentration increases the EE and decreases the loading capacity (LC), whereas the effect of alginate polymer concentration on the release was not observed. The release study of bioactive substances showed that the release kinetics is relatively dependent on the structure and the physicochemical characteristics of the bioactive substance, which became clear when the encapsulated compounds were released from the core of calcium alginate microcapsules. Thus, it could be concluded that the pores size of the Ca-alginate network is smaller than the volume of the crocin molecule (2794.926 Å3) and higher than the volume of the gallic acid molecule (527.659 Å3). For the same microcapsules system, the release mechanism is affected by the structure and physicochemical properties of the encapsulated molecules.

Development and Characterization of Calcium-Alginate Beads of Apigenin: In Vitro Antitumor, Antibacterial, and Antioxidant Activities

The objective of this work was to develop sustained-release Ca-alginate beads of apigenin using sodium alginate, a natural polysaccharide. Six batches were prepared by applying the ionotropic gelation technique, wherein calcium chloride was used as a crosslinking agent. The beads were evaluated for particle size, drug loading, percentage yield, and in vitro drug release. Particle size was found to decrease, and drug entrapment efficiency was enhanced with an increase in the polymer concentration. The dissolution study showed sustained drug release from the apigenin-loaded alginate beads with an increase in the polymer proportion. Based on the dissolution profiles, BD6 formulation was optimized and characterized for FTIR, DSC, XRD, and SEM, results of which indicated successful development of apigenin-loaded Ca alginate beads. MTT assay demonstrated a potential anticancer effect against the breast cancer MCF-7 cell lines. The antimicrobial activity exhibited effective inhibition in the bacterial and fungal growth rate. The DPPH measurement revealed that the formulation had substantial antioxidant activity, with EC50 value slightly lowered compared to pure apigenin. A stability study demonstrated that the BD6 was stable with similar (f2) drug release profiles in harsh condition. In conclusion, alginate-based beads could be used for sustaining the drug release of poorly water-soluble apigenin while also improving in vitro antitumor, antimicrobial, and antioxidant activity.