ORIGINAL RESEARCH PAPER Immobilization of chloroperoxidase on mesoporous materials for the oxidation of 4,6-dimethyldibenzothiophene, a recalcitrant organic sulfur compound present in petroleum fractions Eduardo Terre ´s Æ Mayra Montiel Æ Sylvie Le Borgne Æ Eduardo Torres Received: 1 June 2007 / Revised: 10 August 2007 / Accepted: 15 August 2007 / Published online: 18 September 2007 Ó Springer Science+Business Media B.V. 2007 Abstract The catalytic potential of chloroperoxidase (CPO) immobilized on mesoporous materials was evaluated for the oxidation of 4,6-dimethyldibenzo- thiophene in water/acetonitrile mixtures. Two different types of materials were used for the immobilization: a metal containing Al-MCM-41 material with a pore size of 26 A ˚ and SBA-16 materials with three different pore sizes: 40, 90 and 117 A ˚ . The SBA-16 40 A ˚ did not retain any CPO. The nature and the pore size of the material affected the catalytic activity of the enzyme as well as its stability. Compared to the free enzyme, the thermal stability of CPO at 45°C was two and three times higher than when immobilized on Al-MCM-41 and SBA-16 90 A ˚ , respectively. Keywords Biocatalysis  Chloroperoxidase  Dibenzothiophene  Enzyme immobilization  Mesoporous materials  Petroleum Introduction The removal of recalcitrant organic sulfur compounds, mainly dibenzothiophene (DBT) and its alkylated derivatives, from petroleum and its fractions is neces- sary because of industrial and environmental concerns. Oxidative desulfurization is a possible complementary alternative to the conventional hydrodesulfurization processes for the pre-combustion desulfurization of petroleum derived fuels. Oxidative desulfurization has been successfully applied to remove organic sulfur compounds from diesel and light gas oil (Rang et al. 2006). The selective oxidation of the sulfur atom on the molecule using hydroperoxides or peracids, photo- induced oxidation or ultrasound results in oxidized organosulfur compounds with a higher polarity, reac- tivity and molecular weight, which can be removed by physical or chemical treatmentsto obtain ‘‘sulfur-free’’ fuels (Ishihara et al. 2005; Zannikos et al. 1995; Zapata et al. 2005; Te et al. 2001; Yu et al. 2005). Organosulfur compounds can also be oxidized via biocatalysis (Villasenor et al. 2004; Ayala and Vazquez-Duhalt 2004). Straight-run diesel fuel con- taining 1.6% (w/v) sulfur was enzymatically oxidized with chloroperoxidase (CPO) and the oxidation prod- ucts were removed by distillation. After distillation, the biocatalytically oxidized fuel contained 0.27% sulfur, while the untreated fuel, after the same distillation process, contained 1.27% (Ayala et al. 1994). The enzyme was selective for organosulfur oxidation since the total petroleum hydrocarbon content was only E. Terre ´s  M. Montiel Instituto Mexicano del Petro ´leo, Eje Central La ´zaro Ca ´rdenas 152, 07730 Mexico City, D.F., Mexico S. Le Borgne  E. Torres (&) Departamento de Procesos y Tecnologı ´a, Universidad Auto ´noma Metropolitana – Cuajimalpa, Av. Pedro A. de los Santos 84, Col. San Miguel Chapultepec, 11850 Mexico, D.F., Mexico e-mail: etorres@correo.cua.uam.mx 123 Biotechnol Lett (2008) 30:173–179 DOI 10.1007/s10529-007-9512-5