Raquel G. Nascimento

Bio: Raquel G. Nascimento is an academic researcher from Federal University of Paraíba. The author has contributed to research in topics: Cyanuric chloride & Triazine. The author has an hindex of 1, co-authored 1 publications receiving 7 citations.

Organofunctionalized silica gel as a support for lipase

Abstract: This work described the preparation of silica gel modified with cyanuric chloride. The modified silica gel was tested for the ability to immobilize Burkholderia cepacia lipase. Contact times ranging from 4 to 24 h were investigated to determine the optimal lipase immobilization time. Following immobilization, the enzyme activity was assessed by the hydrolysis of p-nitrophenylpalmitate (pNPP). Elemental analysis data revealed that 0.4 mmol of cyanuric chloride were anchored per gram of support, demonstrating the successful incorporation of the triazine molecule onto the silica surface. The tests of reusability and storage indicated that the enzyme-modified silica-gel (immobilization at 24 h) was more stable under reaction conditions than the other systems. The activity assays indicated high rates of enzymatic formation of p-nitrophenol (p-NP), demonstrating a maximum activity retention of 87%.

Enzymatic synthesis and characterization of polycaprolactone by using immobilized lipase onto a surface-modified renewable carrier

Abstract: Abstract In the present study, rice husk ash, which is a renewable and abundant material, was utilized as a carrier for lipase immobilization for the first time. Poly (ε-caprolactone) synthesis was successfully achieved by the new enzymatic catalyst: Candida antarctica lipase B immobilized onto surface-modified rice husk ashes by covalent binding. It was aimed to obtain optimum polymerization conditions at which highest molecular weight was reached and characterize the polymer produced. Moreover, thermal stability and effectiveness of the new biocatalyst in non-aqueous media were also shown with successful polymerization reactions. In addition, by using the new enzyme preparation, ε-caprolactone was able to be polymerized even at 30°C, which was promising for an energy saving process. Consequently, this work provides a new alternative route for poly (ε-caprolactone) synthesis.

Immobilization of Candida antarctica lipase B (CALB) on surface-modified rice husk ashes (RHA) via physical adsorption and cross-linking methods

Abstract: In the present study, the recovery of activity of Candida antarctica lipase B (CALB) immobilized onto surface-modified rice husk ash (RHA) was 90% for both cross-linking and adsorption methods. Both cross-linked and adsorbed immobilized preparations were very stable, retaining more than 48% of their activity over the range of temperatures studied. The optimum temperature and optimum pH values were 37 °C and 7.0, respectively for both immobilized preparations, while the relative activities after storage at 4.0 °C for 60 days were 55% and 65% using cross-linking and adsorption methods, respectively. Also, the activity of the immobilized lipase began to decrease after 10 cycles, more than 58% of the initial activities were still retained after 10 cycles for both immobilization methods. These results indicated that lipase immobilized by cross-linking and adsorption not only effected activity recovery, but also remarkably effected stability, reusability and application adaptability. It can be concluded...

Blends of amorphous/crystalline nanoalumina and hydrophobic amorphous nanosilica

Abstract: Initial Al-100 and hydro-compacted amorphous/crystalline nanoalumina cAl-100 alone or in blends with hydrophobic amorphous nanosilica AM1 were characterized using low-temperature 1H NMR and IR spectroscopies, adsorption, XRD, DSC, microscopy, and cryoporometry Mechanical treatment of weakly hydrated (05 g/g) nanooxides results in their hydro-compaction changing many of the material characteristics There is overlapping of confined space effects for water bound in voids between nanoparticles with effects caused by the colligative properties of aqueous solution of trifluoroacetic acid in a chloroform medium The interfacial phenomena determine the temperature behavior of bound water/ice depending on dispersion media features Contact area between unfrozen water and nanooxide surface is smaller than the specific surface area due incomplete water filling of voids between hydrophilic/hydrophobic nanoparticles In composites with cAl-100/AM1, there is a tendency of diminution of the contact area of water with hydrophobic nanosilica AM1 and hydrophobic chloroform immiscible with water This effect changes the temperature behavior of water, which becomes more strongly bound to hydrophilic alumina The observed effects can be of importance upon practical applications of nanooxide based composites