Carbon nanotubes are demonstrated as a good support for the immobilization of b-Glucosidase. This is an enzyme with high molecular weight (ca. 135 kDa). A high enzyme loading of 630 mg per gram of support was achieved in 12 h. The link between the enzyme and the carbon nanotubes surface was by electrostatic interactions due to the different charges of the enzyme and the support at the pH of the immobilization. Immobilized b-Glucosidase showed a catalytic activity above 400 U/g on the hydrolysis of 4-nitrophenyl-b-D-glucopyranoside (p-NPG).
Glycerol remains a bottleneck for the biodiesel industry as well as an opportunity from the biorefinery perspective, having a notable reactivity as a platform chemical. In particular, glycerol ketals can be envisaged as oxygenates for fuel formulation. In this study, we have focused on the green synthesis of glycerol ketals by reacting glycerol with acyclic (acetone, butanone) and cyclic (cyclohexanone) ketones in the presence of an acid activated clay Tunisian AC in homogeneous systems under quasi-solventless conditions. These reactions were followed by on-line Fourier Transform Infrared Spectroscopy (FTIR) (namely, ReactIR 10). Firstly, the contacting time was selected studying the activity, stability and chemical characteristics of a set of catalysts. The 1-h activated clay AC was further characterized by X-Ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electronic Microscopy with Energy Dispersive Spectroscopy (SEM/EDS). Finally, the effect of the main operational variables (catalyst concentration, reagents molar ratio, time and temperature) were checked and we reflected on adequate second-order kinetic models with partial first-order deactivation.
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