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ABSTRACT: Ester hydrolysis at oil–water interface by lipase covalently immobilized on ionic liquid-modified magnetic nanoparticles was investigated. Magnetic supports with a diameter of 10–15 nm were synthesized by covalent binding of ionic liquids (chain length C4 and C8 and anions Cl−, BF4−, and PF6−) on the surface of Fe3O4 nanoparticles. Lipase was covalently immobilized on Fe3O4 nanoparticles using ionic liquids as the coupling reagent. Ionic liquid-modified magnetic nanoparticle-grafted lipase preferentially located at the oil–water interface. It has higher catalytic activity than its native counterpart. A modified Michaelis–Menten model was used to elucidate the effect of stirring rate, aqueous–organic phase ratio, total amount of enzyme, and ester chain length. The influences of these conditions on esters hydrolysis at oil–water interface were consistent with the introduction of the ionic liquids interlayer. Ionic liquids could be used to control the oil–water interfacial characteristics during lipase catalyzed hydrolysis, and thus control the behavior of immobilized lipase. © 2011 American Institute of Chemical Engineers AIChE J, 2012
AIChE Journal 05/2011; 58(4):1203 - 1211. · 2.26 Impact Factor
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ABSTRACT: Candida rugosa lipase was immobilized on magnetic nanoparticles supported ionic liquids having different cation chain length (C1, C4 and C8) and anions (Cl−, BF4− and PF6−). Magnetic nanoparticles supported ionic liquids were obtained by covalent bonding of ionic liquids–silane on magnetic silica nanoparticles. The particles are superparamagnetic with diameter of about 55 nm. Large amount of lipase (63.89 mg/(100 mg carrier)) was loaded on the support through ionic adsorption. Activity of the immobilized lipase was examined by the catalysis of esterification between oleic acid and butanol. The activity of bound lipase was 118.3% compared to that of the native lipase. Immobilized lipase maintained 60% of its initial activity even when the temperature was up to 80 °C. In addition, immobilized lipase retained 60% of its initial activity after 8 repeated batches reaction, while no activity was detected after 6 cycles for the free enzyme.
Journal of Molecular Catalysis B: Enzymatic. 01/2009; 58:103-109.
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ABSTRACT: a b s t r a c t In this study, terminal modified poly(ethylene glycerol) (PEG) was employed as the phase-forming polymer to construct aqueous two-phase (ATP). After the phase equilibrium, 95.8% penicillin could be extracted into imidazole-terminal PEG-rich phase efficiently. Imidazole-terminal PEG (I-PEG) was sepa-rated from the aqueous phase containing penicillin to hydrophobic ionic liquid phase at basic pH, and a weak acidic aqueous phase was then employed to recover the I-PEG from the hydrophobic ionic liquid phase into water at pH 5.5–6. The recycle of the polymer was achieved with the aid of hydrophobic ionic liquids.
Chemical Engineering Journal. 01/2009; 147:22-26.
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ABSTRACT: A dodecane/thermosensitive polymer/water three-liquid-phase system was introduced for enzymatic hydrolysis of penicillin G (Pen G) for 6-aminopenicillanic acid (6-APA). The enzyme was covalently attached to the terminal of PEO-PPO-PEO polymer (L63), which would be transferred into a polymer coacervate phase at high temperature above its "cloud point". 6-APA was primarily resided in the aqueous phase due to its zwitterionic nature. More than 70% phenylacetic acid (PAA) was transferred into the organic phase using trioctylmethylammonium hydroxide and trihexyl-(tetradecyl)phosphonium bis 2,4,4-trimethylpentylphosphinate ionic liquids (Cyphos IL-104) mixture at pH 5.5, while most of Pen G resided in water. As a result, high operational pH was permitted in three-liquid-phase system, which leads to higher enzymatic activity (120 IU at 40 degrees C) and stability (enzymatic half-time up to 55 h at 60 degrees C) in comparison with the value in butyl acetate/water two-phase system. On the other hand, two products in three-liquid-phase system might be automatically separated from the enzyme sphere into different phases at the same time, which facilitated the reaction equilibrium towards the product's side with 6-APA productivity of 80% at 42 degrees C, pH 5.5.
Applied Biochemistry and Biotechnology 03/2008; 144(2):145-59. · 1.94 Impact Factor
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ABSTRACT: In this work, oligopeptide was covalently bonded on the surface of magnetic particles through an ionic liquids spacer. When ionic liquids containing bulky cations with strong H-bonding ability or having hydrophobic anions were used, the yield and enantioselectivity of aldol reaction were enhanced greatly. Introducing an ionic liquids spacer between the oligopeptide and magnetic resin decreased the minimum number of amino acids for optimizing the efficiency of aldol addition. Varying the amino acid sequence of the oligopeptide showed limited effect on the yield and enantioselectivity; however, introducing a series of lysine groups on the terminal of the oligopeptide, close to the imidazolium ring, would significantly increase the output. The magnetite-loaded oligopeptide had a broader substrate range for ketone donor but restricted the enantioselectivity of aldehyde acceptor than the free oligopeptide. The combinative unit served as a recyclable catalyst for aldol addition of ketone and aldehyde, and its catalytic efficiency and selectivity can be finely designed by the characteristics of each part of the catalyst.
Ind. Eng. Chem. Res. 01/2008; 47:9628-9635.
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ABSTRACT: Here, we have reported a new approach for utilizing oleic acid-Pluronic L-64 block copolymer coated iron
oxide nanoparticles as supports for enzyme immobilization. Iron oxide nanoparticles were prepared by a
coprecipitation method and were coated with oleic acid and Pluronic to achieve higher stability and
dispersibility. The surface morphology and size of the particle, as determined by transmission electron
microscopy (TEM), was (10 nm. X-ray diffraction (XRD) patterns were taken over a range from 10° to 90°
2θ, using Cu KR radiation. Saturation magnetization values, measured at 300 K, varied from 34.6 emu/g to
60.8 emu/g. The possible interaction behavior of oleic acid and Pluronic was observed by Fourier transform
infrared (FTIR) analysis and nuclear magnetic resonance (NMR) studies. Further potential of this material as
a support for lipase immobilization and enzymatic hydrolysis at the oil/water interface was also investigated.
The features of the surface-coated magnetic particles enable the adsorption of lipase from Candida cylindraces
via strong hydrophobic interactions, which enhances the stability of the adsorbed enzyme molecules. The
stability of the catalyst and, hence, its industrial applicability was tested by performing subsequent reaction
cycles for the hydrolysis of olive oil. The activity of the immobilized lipase, pretreated with its substrate, was
510 U/g-matrix and was observed to be maintained at levels as high as 90% of its original activity for up to
at least seven reuses.
Ind. Eng. Chem. Res.,. 01/2008; 47:6379–6385.
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ABSTRACT: Effect of 1-butyl-3-methyl-imidazolium bromide (BmimBr) on the aggregation behavior of PEO-PPO-PEO Pluronic P104 aqueous solution was studied by Fourier transform infrared (FTIR) spectroscopy, freeze fracture transmission electron microscopy (FF-TEM), dynamic light scattering (DLS), and NMR spectroscopy. When the BmimBr concentration was below 1.232 mol/L, the critical micelle temperature (CMT) of Pluronic P104 remained constant, while the size of micelles increased with increasing the BmimBr concentration; above this concentration, the CMT of Pluronic P104 decreased abruptly, and bigger clusters of BmimBr were formed. The selective nuclear Overhauser effect (NOE) spectrum indicates that the PO block of the P104 interacts with the butyl group of the Bmim+ cation by hydrophobic interaction. It suggests that when the concentration of BmimBr is below 1.232 mol/L, there are P104 micelles in the aqueous solution with BmimBr embedding to the micellar core, while above this concentration, P104 micelles and BmimBr clusters coexist in the system.
The Journal of Physical Chemistry B 03/2007; 111(6):1327-33. · 3.70 Impact Factor
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ABSTRACT: In this paper, an integrated process based on hydrophilic and hydrophobic ionic liquids is proposed to extract penicillin G from its fermentation broth and recover it into fresh water. With the aid of buffer salt, hydrophilic ionic liquids [C4mim]BF4(1-butyl-3-methylimidazolium tetrafluoraborate) could form an ionic liquids aqueous two-phase system (ILATPS) and extract penicillin into the ionic liquids-rich phase of ILATPS, while leaving miscellaneous proteins in the ionic liquids-poor phase. Subsequently, hydrophobic [C4mim]PF6 (1-butyl-3-methylimidazolium hexafluoraphosphate) is introduced into the ionic liquids-rich phase of ILATPS, which transfers the system into a hydrophobic ionic liquids phase in equilibrium with a water-phase system (HOILWS). The majority of hydrophilic [C4mim]BF4 is transferred into the ionic liquids-rich phase of HOILWS, leaving most of the penicillin in the conjugated water phase. In comparison with the butyl acetate/water system or the polymer−aqueous two-phase system, the integrated ionic liquids system shows several advantages: (1) Penicillin is efficiently extracted into the ionic liquids-rich phase at neutral pH, so the protein emulsification met in the organic solvent system is avoided. (2) Hydrophobic ionic liquids could separate hydrophilic ionic liquids away from the penicillin-containing aqueous phase. Consequently, the trouble for recovering the phase-forming material in the polymer−aqueous two-phase system is overcome. Moreover, the experimental results suggest that the partitioning behaviors of penicillin in ILATPS and HOILWS are different. In ILATPS, the logarithm of the partitioning ratio of penicillin (ln K) increases proportionally with the concentration difference of ionic liquids between ionic liquids-rich and liquids-poor phases (Δ[ionic liquids]), and the partitioning ratio exceeds 1000 at Δ[ionic liquids] = 2.5 mol/L. While in HOILWS, ln K decreases monotonically with Δ[ionic liquids], and more than 90% penicillin could be recovered from the ionic liquids-rich phase of ILATPS when the mole ratio of [C4mim]PF6/[C4mim]BF4 exceeds 1. Moreover, the partitioning ratio approaches that in the [C4mim]PF6/water system when the [C4mim]PF6/[C4mim]BF4 ratio in HOILWS is sufficiently large. A modified Flory−Huggins model is proposed to elucidate the partitioning behaviors in the two ionic liquids systems, which emphasizes the key role of energic equilibrium in determining ln K ionic liquids solution. In ILATPS, the distance between ionic liquids aggregates is relatively large, which makes the long-range “self-energy” dominating the partitioning behaviors of penicillin. In contrast, in HOILWS the distance between ionic liquids aggregates is greatly suppressed, which magnifies the entropic loss and hydration repulsion between ionic liquids aggregates and makes them as determinants for the partitioning of penicillin in HOILWS. The conclusions from this model are validated by a series of experimental observations, including the salt's type and concentration, hydrophobic/hydrophilic ionic liquids ratio, and ionic liquids species.
Ind. Eng. Chem. Res. 01/2007; 46:6303–6312.
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ABSTRACT: The physicochemical features of the Winsor II reverse-micelle system, using long-chain ionic liquid (ILRM) as the surfactant, and their behavior toward the partitioning ratio (D) of penicillin were investigated in this work. It was determined that log D increases proportionally with the reciprocal of W0 (which is the molar ratio of water to the ionic liquids surfactant in the organic phase of ILRM), and the slope and intercept of the graph of log D vs 1/W0 are functions of the architectural properties in ILRM. For example, when the hydrophobicity in the poor district in ionic liquids microemulsion is enhanced using a chaotropic inorganic salt or C2-methylated ionic liquids, the slope rises evidently, although the intercept remains almost constant. In contrast, the intercept increases in microemulsions that contain organic solvent with small molecular size, ionic liquids with high concentration, or short side-chains, all of which contribute to the highly ordered nature of the hydrocarbon chain of ionic liquids, despite the slope remaining constant. The respective relationships of the head-phile and tail-phile parameters on the slope and intercept of log D vs 1/W0 could be understood with their roles on the lipophilic−hydrophilic balance in ILRM. Those parameters close to the “water pool” intend to change the compactness in an interfacial film, but leave the chain conformation constant. Nevertheless, the tail-philic groups, because of their isolation from the water pool, do not change the slope of the log D vs 1/W0 line but primarily changes the intercept. The intrinsic relationships between the enthalpic/entropic energies in the interface and the slope/intercept of log D vs 1/W0 could contribute a better platform to understand the intrinsic mechanism of the partitioning behavior in ILRM.
Ind. Eng. Chem. Res. 01/2007; 46:2112-2116.
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ABSTRACT: A magnetically rotational reactor (MRR) has been developed and used in absorbing benzene emissions. The MRR has a permanent magnet core and uses magnetic ionic liquid [bmim]FeCl4 as absorbent. Benzene emissions were carried by N2 into the MRR and were absorbed by the magnetic ionic liquid. The rotation of the permanent magnet core provided impetus for the agitation of the magnetic ionic liquid, enhancing mass transfer and making benzene better dispersed in the absorbent. 0.68 g benzene emissions could be absorbed by a gram of [bmim]FeCl4, 0.27 and 0.40 g/g higher than that by [bmim]PF6 and [bmim]BF4, respectively. The absorption rate increased with increasing rotation rate of the permanent magnet.
China Particuology.
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ABSTRACT: In this paper, an integrated process involving the mixed ionic liquids/water two-phase system (MILWS) is proposed to improve the efficiency for enzymatic hydrolysis of penicillin G. First, hydrophilic [C4mim]BF4 (1-butyl-3-methylimidazolium tetrafluoraborate) and NaH2PO4 salt form an ionic liquids aqueous two-phase system (ILATPS), which could extract penicillin from its fermentation broth efficiently. Second, a hydrophobic [C4mim]PF6 (1-butyl-3-methylimidazolium hexafluoraphosphate) is introduced into the ionic liquids-rich phase of ILATPS containing penicillin and converses it into MILWS. Penicillin is hydrolyzed by penicillin acylase in the water phase of MILWS at pH 5. The byproduct phenylacetic acid (PAA) is partitioned into the ionic liquids mixture phase, while the intended product 6-aminopenicillanic acid (6-APA) is precipitated at this pH. In comparison with a similar butyl acetate/water system (BAWS) at pH 4, MILWS exhibits two advantages. (1) The selectivity between PAA and penicillin is greatly optimized at pH 5 by varying the mole ratio of [C4mim]PF6/[C4mim]BF4 in MILWS, whereas in BAWS the unalterable nature of the organic solvent restricts the optimized pH for maximum selectivity between PAA and penicillin at pH 4. (2) The pH for 6-APA precipitation in BAWS is 4, whereas it shifts to pH 5 in MILWS due to the complexation between negatively charged 6-APA and the cationic surface of the ionic liquids micelle. As a result, the removal of the two products from the enzyme sphere at relatively high pH is permitted in MILWS, which is beneficial for enzymatic activity and stability in comparison with the acidic pH 4 environment in BAWS.
Biotechnology Progress 23(4):829-35. · 2.34 Impact Factor
