Immobilization of halophilic Aspergillus awamori EM66 exochitinase on grafted k-carrageenan-alginate beads

A novel extreme halophilic exochitinase enzyme was produced by honey isolate Aspergillus awamori EM66. The enzyme was immobilized successfully on k-carrageenan-alginate gel carrier (CA) with 93 % immobilization yield. The immobilization process significantly improved the enzyme specific activity 2.6-fold compared to the free form. The significant factors influencing the immobilization process such as enzyme protein concentration and loading time were studied. Distinguishable characteristics of optimum pH and temperature, stability at different temperatures and NaCl tolerance for free and immobilized enzyme were studied. The immobilization process improved optimum temperature from 35 to 45 °C. The immobilized enzyme retained 76.70 % of its activity after 2 h at 75 °C compared to complete loss of activity for the free enzyme. The reusability test proved the durability of the CA gel beads for 28 cycles without losing its activity

Broadband MIR harvester using silicon nanostructures

Abstract In this work, we propose an all-silicon-based super absorber in the mid infrared (MIR) spectral range. The presented structures are composed of n-doped silicon nanoparticles or nanowires embedded in intrinsic silicon. An intense absorption peak is observed and could be tuned across the MIR range. While nanoparticles give a single broad absorption peak, the nanowires structure shows a broadband absorption of more than 70% from λ = 5 to 13 µm reaching up to 99% at 7 µm. The absorption peak could be extended to more than 20 µm by increasing the length of the nanowire. Increasing the diameter of the nanoparticles gives higher absorption, reaching just above 90% efficiency at λ = 11 µm for a diameter of 1500 nm. Changing the geometrical parameters of each structure is thoroughly studied and analyzed to obtain highest absorption in MIR. The proposed structures are CMOS compatible, have small footprints and could be integrated for on-chip applications

Optimal immobilization of ß -galactosidase onto -carrageenan gel beads using response surface methodology and its applications

ß-Galactosidase (ß-gal) was immobilized by covalent binding on novel -carrageenan gel beads activated by two-step method; the gel beads were soaked in polyethyleneimine followed by glutaraldehyde. 22 full-factorial central composite experiment designs were employed to optimize the conditions for the maximum enzyme loading efficiency. 11.443 U of enzyme/g gel beads was achieved by soaking 40 units of enzyme with the gel beads for eight hours. Immobilization process increased the pH from 4.5 to 5.5 and operational temperature from 50 to 55°C compared to the free enzyme. The apparent Km after immobilization was 61.6 mM compared to 22.9 mM for free enzyme. Maximum velocity Vmax was 131.2 mol·min-1 while it was 177.1 mol·min-1 for free enzyme. The full conversion experiment showed that the immobilized enzyme form is active as that of the free enzyme as both of them reached their maximum 100% relative hydrolysis at 4 h. The reusability test proved the durability of the -carrageenan beads loaded with ß-galactosidase for 20 cycles with retention of 60% of the immobilized enzyme activity to be more convenient for industrial uses. © 2014 Magdy M. Elnashar et al