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Lipases from Rhizomucor miehei (RmL) and Candida antartica (CaL-B) entrapped in surfactant free microemulsion-like ternary systems consisting of n-hexane, short chain alcohols (1-propanol or 2-methyl-2-propanol) and water, keep their catalytic activity at 30 degrees C, catalyzing efficiently the esterification of fatty acids or natural phenolic acids including cinnamic acid derivatives. High conversions (up to 95%) were obtained with both lipases entrapped in various ternary systems. Lipases catalytic efficiency and stability was influenced by the composition of the ternary systems used. Hydroxypropylmethyl cellulose (HPMC) microemulsions-based organogels (MBGs) formulated with various surfactant free microemulsion-like systems were used as a matrix for enzyme immobilization. These lipase-containing MBGs prove to be a novel solid-phase catalyst for use, under mild conditions, in non-polar solvents as well as in solvent free systems. CaL-B immobilized in surfactant free MBGs keep its catalytic activity for a storage period of 8 months, while the corresponding residual activity of immobilized RmL was decreased by 50%. The stability of enzymes in such surfactant free MBGs is higher than that observed in MBGs formulated with surfactant based w/o microemulsions. Lipases-containing surfactant free MBGs were used in seven consecutive batch syntheses of fatty esters with only 10-15% loss of activity. (c) 2005 Elsevier Inc. All rights reserved. Enzyme and Microbial Technology

Water-in-ionic liquid (w/IL) microemulsions formulated with non-ionic surfactants, (Tween 20 or Triton X-100) in 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim]PF(6)), were used as media for lipase-catalyzed esterification reactions. The catalytic behavior and stability of lipases from Candida rugosa, Chromobacterium viscosum and Thermomyces lanuginosa in these novel microemulsions were investigated and compared to other microheterogeneous media used so far for enzyme-catalyzed reactions. The catalytic behavior of the enzymes depends strongly on the surfactant concentration and the water content. The dependence of the esterification activity of lipases on molar ratio of water to surfactant (w(o)) follows a bell-shaped profile, presenting a maximum at w(o) approximate to 5. The operational stability of lipases in w/IL microemulsions, especially at high incubation temperature (50 degrees C), was significantly increased compared to that observed in other microheterogeneous media. The highest half-life times (>100 h) were obtained in w/IL microemulsions with low water content. Conformational studies via Fourier transform-infrared (FT-IR) and circular dichroism (CD) spectroscopy indicated that lipases entrapped in w/IL microemulsions in most cases retain their native structure or adapt a more rigid structure compared to other microheterogeneous media, which correlated well with the stability results. A simple procedure suitable for ester separation and enzyme reuse was developed. T lanuginosa lipase retained 90% of activity after ten reaction cycles in w/IL microemulsions formulated with Tween 20. (C) 2009 Elsevier B.V. All rights reserved. Journal of Molecular Catalysis B-Enzymatic

Surfactant free ternary systems formulated with organic solvents such as alpha-pinene or n-hexane, short chain alcohols and water, were used as new reaction media to maximize the catalytic performance of chloroperoxidase from Caldariomyces fumago (CPO) towards the oxidation of hydrophobic compounds including olefins and terpenols. The influence of the composition and the hydration state of the system, the nature of the oxidizing agent as well as substrate availability on the catalytic behavior and stability of the enzyme was investigated, using the chlorination of monochlorodimedone (MCD) and the epoxidation of styrene as model reactions. Based on residual chlorination activity measurements, which were in accordance with differential scanning calorimetry (DSC) findings, it was concluded that in low water systems formulated with alpha-pinene CPO stability is significantly increased compared to other reaction media (up to 65% residual activity after 24 h of incubation at 30 degrees C). Electron paramagnetic resonance (EPR) spectroscopy indicated that in low water content systems the ferric environment of the active site of CPO does not undergo severe modifications. Total turnover numbers (TTN) obtained for the oxidation of various olefins and terpenols in alpha-pinene-based systems, were up to 25,000 which is 2-170 times higher than previously reported values. The results indicate that such ternary systems can be efficiently employed as reaction media leading to highly enhanced stability and increase CPO potential as practical catalyst for oxidation of large amounts of hydrophobic compounds in a single-step biocatalytic process. (c) 2007 Elsevier B.V. All rights reserved. Journal of Molecular Catalysis B-Enzymatic