The Evaluation of Cellulose Acetate Capsules Functionalized for the Removal of Cd(II).

Cellulose acetate is derived from cellulose and has the characteristics of biodegradability and reusability. So, it has been used for the elimination of toxic compounds capable of producing different diseases, such as cadmium, that result from human and industrial activity. For this reason, capsules functionalized with Cyanex 923 were prepared and characterized by FTIR spectroscopy, Energy Dispersive X-ray Spectroscopy (EDX), and SEM. The functionalized capsules were used for removing and recovering Cd(II) by modifying variables such as HCl concentration in the extraction medium and carrier content in the capsules, among others. The extraction of cadmium from battery leachates and the three isotherm models, Langmuir, Freundlich, and Dubinin Radushkevich, were also tested to model the cadmium removal process. The results showed a favorable physical sorption with a good capacity for extraction and the possibility of reusing the capsules for up to seven cycles without a decrease in the percentage of cadmium recovery.

Reuse of pacemakers and implantable cardioverter-defibrillators: systematic review, meta-analysis and quality assessment of the body of evidence.

BACKGROUND: Pacemakers (PMs) and implantable cardioverter-defibrillators (ICDs) have reduced mortality and improved the quality of life of cardiac patients. However, the high cost of these devices prevents their large-scale incorporation, particularly in low-income countries, where reusing explanted PMs/ICDs has become an alternative. METHODS: A systematic review and meta-analysis were conducted of studies that compare infection rates, device-related deaths, malfunction and premature battery depletion in patients with reused PM and ICD implants and those with new devices. The quality of the body of evidence was assessed using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) framework. RESULTS: The meta-analysis demonstrated no significant intergroup differences in infection rates (OR 0.98; 95% CI 0.60-1.60), device malfunction (OR 1.58; 95% CI 0.56-4.48) or premature battery depletion (OR 1.96; 95% CI 0.81-4.72) and no device-related deaths. Based on GRADE assessment, confidence in estimates for the outcomes infection rate and device-related death was rated as moderate. CONCLUSION: The results of this analysis enabled us to conclude that PMs and ICDs can be safely and effectively reused. As such, every effort should be made to overcome regulatory, technical and ethical barriers to ensure implantation.

Immobilization of endoglucanase on kaolin by adsorption and covalent bonding.

In the current research, endoglucanase, one of the enzymes of the cellulolytic complex, was immobilized on kaolin by two different techniques, adsorption, and covalent bonding. A comparative study was conducted between free, adsorbed, and covalently immobilized endoglucanase. For the covalent bonding, the kaolin particles were functionalized with 3-aminopropyltriethoxysilane (APTES) and activated with glutaraldehyde. Immobilization by adsorption was performed using the kaolin without any treatment. Recovered activities after the endoglucanase immobilization by adsorption and covalent bonding were found to be 60 ± 2.5 and 65 ± 3.5%, respectively. The studies of optima pH and temperature, as well as thermal stability, showed that the catalytic characteristic of the enzyme was maintained after the immobilization by both adsorption and covalent bonding. Even after 8 cycles of use, the endoglucanase immobilized by the two techniques retained about 86% of its initial activity. The results showed that the adsorption was as effective as covalent bonding for the immobilization of endoglucanase on kaolin. However, the adsorption technique seems to have a greater potential for use in future studies, as it is simpler, cheaper, and faster than covalent immobilization. Therefore, in this work it was demonstrated that endoglucanases can be immobilized efficiently on kaolin through a very simple immobilization protocol, offering a promising strategy for performing repeated enzymatic hydrolysis reactions.

LXYL-P1-2 immobilized on magnetic nanoparticles and its potential application in paclitaxel production

BACKGROUND: LXYL-P1-2 is the first reported glycoside hydrolase that can catalyze the transformation of 7-b-xylosyl-10-deacetyltaxol (XDT) to 10-deacetyltaxol (DT) by removing the D-xylosyl group at the C7 position. Successful synthesis of paclitaxel by one-pot method combining the LXYL-P1-2 and 10- deacetylbaccatin III-10-b-O-acetyltransferase (DBAT) using XDT as a precursor, making LXYL-P1-2 a highly promising enzyme for the industrial production of paclitaxel. The aim of this study was to investigate the catalytic potential of LXYL-P1-2 stabilized on magnetic nanoparticles, the surface of which was modified by Ni2+-immobilized cross-linked Fe3O4@Histidine. RESULTS: The diameter of matrix was 20­40 nm. The Km value of the immobilized LXYL-P1-2 catalyzing XDT (0.145 mM) was lower than that of the free enzyme (0.452 mM), and the kcat/Km value of immobilized enzyme (12.952 mM s 1 ) was higher than the free form (8.622 mM s 1 ). The immobilized form maintained 50% of its original activity after 15 cycles of reuse. In addition, the stability of immobilized LXYL-P1-2, maintained 84.67% of its initial activity, improved in comparison with free form after 30 d storage at 4 C. CONCLUSIONS: This investigation not only provides an effective procedure for biocatalytic production of DT, but also gives an insight into the application of magnetic material immobilization technology.

Whole Cell Entrapment Techniques.

Microbial whole cells are efficient, ecological, and low-cost catalysts that have been successfully applied in the pharmaceutical, environmental, and alimentary industries, among others.Microorganism immobilization is a good way to carry out the bioprocess under preparative conditions. The main advantages of this methodology lie in their high operational stability, easy upstream separation, and bioprocess scale-up feasibility.Cell entrapment is the most widely used technique for whole cell immobilization. This technique-in which the cells are included within a rigid network-is porous enough to allow the diffusion of substrates and products, protects the selected microorganism from the reaction medium, and has high immobilization efficiency (100% in most cases).

Saccharification of citrus wastes by immobilized polygalacturonase in an improved alginate matrix.

Enzyme immobilization using hydrogels is a low-cost and effective system for the degradation of bulk pectin derived from orange industry residues. Polygalacturonases obtained from four different bacterial strains of Streptomyces genus were immobilized in alginate gel and assayed for pectin hydrolysis. The enzyme from Streptomyces halstedii ATCC 10897 proved to be superior and more stable within the alginate matrix. Furthermore, a new strategy to improve alginate bead stability using a mixture of calcium and strontium is reported; this technique allowed enhancing the mechanical properties by combining different amounts of these cations for ionotropic gelation. The developed biocatalyst showed maximum hydrolysis at 2 h, generating 1.54 mg/mL of reducing sugars and decreasing the viscosity of polygalacturonic acid by 98.9%. Reusability up to 29 successive reactions (58 h) demonstrated a very stable performance. The heterogeneous biocatalyst was used in the enzymatic saccharification of orange peel albedo (2.23 mg/mL) for adding value to this agro-waste by industrial exploitation.

Characteristics of Immobilized Urease on Grafted Alginate Bead Systems

This study evaluated the biological importance of immobilized urease enzyme over the free urease. The support material used for urease immobilization was alginate. Generally, the immobilization of urease in alginate gel showed a marked increase in Km and Vmax. However, the immobilized urease showed higher thermal stability than that of free enzyme. The rate of thermal inactivation of the immobilized enzyme decreased due to entrapment in gel matrix. Also, the activity of the immobilized urease was more stable in retention than that of the free enzyme during the storage in solution, although the activity of the immobilized enzyme was lower in comparison with the free enzyme. A stable immobilized system and long storage life are convenient for applications that would not be feasible with a soluble enzyme system. These results highlighted the technical and biochemical benefits of immobilized urease over the free enzyme.