Hydrolysis of Alkyl Ester on Lipase/Silicalite-1 Catalyst

  • PDF / 657,016 Bytes
  • 10 Pages / 595.276 x 790.866 pts Page_size
  • 18 Downloads / 198 Views

DOWNLOAD

REPORT


Hydrolysis of Alkyl Ester on Lipase/Silicalite-1 Catalyst Anastasia Macario Æ Girolamo Giordano Æ Patrizia Frontera Æ Fortunato Crea Æ Leonardo Setti

Received: 29 August 2007 / Accepted: 22 October 2007 / Published online: 8 November 2007 Ó Springer Science+Business Media, LLC 2007

Abstract Pure silica zeolites have been prepared in powder and pellets form with different surface chemical properties in order to investigate how the binding forces in the lipase enzyme adsorption influence the final conformation of the immobilized enzyme and its catalytic activity. The catalytic activity of the adsorbed lipase have been tested in the alkyl esters hydrolysis reaction. The higher alkyl-esters conversion is observed for the lipase immobilized on the supports prepared in OH- media compared to the fluoride media supports. The obtained results can be explained by the two different non-covalent interactions between the external surface of zeolites and the enzyme. Keywords Rhizomucor miehei Lipase  Immobilization  Silicalite-1  Alkyl ester hydrolysis  Self-bonded pellets

1 Introduction Lipases constitute an important class of high selectivity and stereo-specificity industrial enzymes and are currently used in a wide variety of applications: bio-transformation of fats and oils, polymer synthesis and preparation of esters for A. Macario  G. Giordano  F. Crea Dip. Ingegneria Chimica&Materiali, Universita` della Calabria, via P. Bucci, 87036 Rende (CS), Italy P. Frontera (&) Dip. Meccanica&Materiali, Universita` degli Studi Mediterranea di Reggio Calabria, via Graziella, 89100 Reggio Calabria, Italy e-mail: [email protected] L. Setti Dip. Chimica Industriale&Materiali, Universita` degli Studi di Bologna, viale del Risorgimento, 40136 Bologna, Italy

food, for cosmetic industry and for diesel engine fuels (biodiesel ester) as well as for the production of optically pure compounds for the pharmaceutical industry [1–9]. The biological function of lipases is to catalyze the hydrolysis of esters, but they are also able of catalyzing the reverse reaction, achieving esterification, transesterification in various solvents. In order to use lipases more economically and efficiently immobilization techniques can be applied. In fact the immobilization of enzyme ensures the reusability of immobilized lipase, minimizes the cost of product isolation, provides operational flexibility, and the immobilization also increases enzyme thermal and chemical stability. Recent studies have demonstrated that the immobilized lipases, adsorbed on hydrophobic supports, exhibit in the alkyl esters hydrolysis reaction a clear hyper-activation compared to the soluble enzyme due to the interfacial activation [10, 11]. This interfacial activation is caused by the conformation change resulting from the adsorption. From X-ray crystallographic studies [12, 13] the crystal and molecular structure of a triacylglycerol lipase has been elucidated. Insofar, the particular and well known conformation of lipase enzyme suggests that the most suitable immobiliz