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Enzymatic synthesis of xylitol fatty acid ester was performed in hexane using Novozym 435 (immobilized Candida antarctica lipase on macroporous resin). Taguchi method based on three levels, six variables L27 orthogonal array robust design was implemented to optimize experimental conditions. The effects of reaction parameters including reaction time (7-24 h), enzyme amount (0.05-0.3 g), temperature (30-60 °C), amount of molecular sieve (1-4 g), substrate molar ratio (0.3-1) and xylitol concentration (0.005-0.015 g/ml) on the percentage yield of sugar ester were investigated. The optimum conditions derived via Taguchi method were: reaction time 7 h, temperature 60 °C, amount of enzyme 0.12 g, amount of molecular sieve 2.5 g, substrate molar ratio 1 and xylitol concentration 0.015 g/ml. The actual experimental yield was 96.10% under optimum condition, which compared well to the maximum predicted value of 96.27%.

We report on the synthesis of ZnO nanoplates and ZnO nanoplate/Ag nanoparticle heterostructures via a simple and cost effective wet chemical precipitation method. The prepared samples were characterized for structural and optical properties by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), UV-VIS reflectance, Raman, and FT-IR spectroscopy. The Kramers Kronig (K K) method and classical dispersion theory was applied to calculate the far-infrared optical constants such as, refractive index n(u), dielectric constant 3(u), transverse optical phonon (TO) and longitudinal (LO) optical phonon modes. We determined various optical constant values n(u) and 3(u) for ZnO nanostructures in the range of 0 to 9 and 0 to 70, respectively. Whereas, for Ag deposition on ZnO nanostructures, the corresponding n(u) and 3(u) values were found to be increased in the range of 0 to 30 and 0 to 800, respectively. The TO and LO optical phonon modes of ZnO nanoplate/Ag nanoparticle heterostructures were also found to be higher (416 cm 1 , 620 cm

Immobilized Candida antarctica lipase B-catalyzed esterification of xylitol and two fatty acids (capric and caproic acid) were studied in a solvent-free system. The Taguchi orthogonal array method based on three-level-four-variables with nine experiments was applied for the analysis and optimization of the reaction parameters including time, substrate molar ratio, amount of enzyme, and amount of molecular sieve. The obtained conversion was higher in the esterification of xylitol and capric acid with longer chain length. The optimum conditions derived via the Taguchi approach for the synthesis of xylitol caprate and xylitol caproate were reaction time, 29 and 18h; substrate molar ratio, 0.3 and 1.0; enzyme amount, 0.20 and 0.05g, and molecular sieve amount of 0.03g, respectively. The good correlation between the predicted conversions (74.18% and 61.23%) and the actual values (74.05% and 60.5%) shows that the model derived from the Taguchi orthogonal array can be used for optimization and better understanding of the effect of reaction parameters on the enzymatic synthesis of xylitol esters in a solvent-free system.