- Synthesis of polyesters containing disiloxane subunits: Structural characterization, kinetics, and an examination of the thermal tolerance of Novozym-435
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This paper reports the Novozym-435 mediated polymerization of disiloxane-containing polyester monomers under solvent-free conditions. The thermal tolerance of the immobilized enzyme was examined by conducting polymerization cycles over a temperature range of 35-150 °C. Increasing the temperature up to 100 °C afforded an increase in the apparent second order rate constant. Residual activity was measured using the production of octyl palmitate. The enzyme was shown to retain on average greater than 90% of its residual activity regardless of the polymerization temperature. This prompted a study of the long term thermal tolerance of the biocatalyst in which it was determined that over ten reaction cycles there was a significant decrease in the initial polymerization rate, but no change in the degree of monomer conversion after 24 h. The disiloxane containing polyesters were characterized using nuclear magnetic resonance spectroscopy and Fourier-transform infrared spectroscopy. Differential scanning calorimetry was used to determine the thermal properties of the disiloxane-containing polyesters.
- Frampton, Mark B.,Séguin, Jacqueline P.,Marquardt, Drew,Harroun, Thad A.,Zelisko, Paul M.
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- Carbocatalysis: N-doped reduced graphene oxide catalyzed esterification of fatty acids with long chain alcohols
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Nitrogen doped reduced graphene oxide (N-rGO), 5.8% N readily synthesized from the thermal annealing of graphene oxide (GO) in ammonium hydroxide at 453 K, was demonstrated to be a superior metal-free non-acidic carbo-catalyst for the esterification of fatty acids with different alcohols. The effect of various reaction parameters such as reaction temperature, reaction time, catalyst amount etc. has been studied. The developed catalyst was found to be highly stable and exhibited consistent reusability for seven cycles without any significant decrease in the product yields.
- Porwal, Jyoti,Karanwal, Neha,Kaul, Savita,Jain, Suman L.
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- Characterization, performance, and applications of a yeast surface display-based biocatalyst
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This work demonstrates the efficacy and cost effectiveness of yeast surface display (YSD) as a method for producing and purifying enzyme catalysts. Lipase B from Candida antarctica (CalB) and lipase from Photobacterium lipolyticum sp. M37 (M37L) were individually displayed on the surface of yeasts via fusion with alpha-agglutinin. The enzyme is produced, purified, and immobilized in a single step. The population expressing the enzyme was quantified by flow cytometry. After lyophilization, the hydrolytic activity of the biocatalyst was assayed with p-nitrophenyl butyrate and p-nitrophenyl palmitate substrates. Esterification reactions involving octanoic acid and either butanol or octanol were used to evaluate esterification activity. The lyophilized YSD biocatalyst hydrolytic activity matched or exceeded commercial lipase (Novozym 435) immobilized on acrylic resin at equal catalyst loading, and achieved esterification levels 10-50% that of Novozyme 435. Factoring in the cost of production, the YSD biocatalyst represents a considerable savings over traditionally prepared and purchased enzyme catalysts. This promises to significantly expand the catalytic applications of immobilized lipases, and immobilized enzymes more generally, in commercial processes. This journal is
- Eby,Peretti
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p. 19166 - 19175
(2015/06/15)
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- Esterifications of carboxylic acids and alcohols catalyzed by Al 2(SO4)3 · 18H2O under solvent-free condition
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Esterifications of equimolar mixture of carboxylic acids and alcohols can be effectively catalyzed by Al2(SO4)3 · 18H2O under solvent-free condition. The esterification catalyzed by Al2(SO4)3 · 18H2O is a promising green method thanks to no need of organic solvent, no pollution, no causticity and ease to handle after reaction. This catalyst is of a low toxicity (usually it is used as purifying agent for drinking water), low-cost compound and is easily separated from the reaction mixture by simple filtration. Moreover, the catalyst can be recycled for the further esterification and the conversion does not evidently decrease.
- Gang, Li,Wenhui, Pang
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experimental part
p. 559 - 565
(2011/01/07)
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- Liquid-liquid biphasic synthesis of long chain wax esters using the Lewis acidic ionic liquid choline chloride·2ZnCl2
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The first liquid-liquid biphasic synthesis of wax esters in a Lewis acidic ionic liquid, choline chloride·2ZnCl2 by the esterification of long chain carboxylic acids with long chain alcohols is described. The reported reaction system has the advantages of both homogeneous and heterogeneous catalysis with high product yield and the ease of product as well as catalyst separation without the use of an organic solvent. The ionic liquid studied plays the dual role of solvent as well as catalyst and is recycled up to six times without any significant loss of activity.
- Sunitha, Sadula,Kanjilal, Sanjit,Reddy, P. Srinivasa,Prasad, Rachapudi B.N.
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p. 6962 - 6965
(2008/02/13)
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- Process for producing esters employing hydrolyzable catalysts
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A process for producing esters wherein a carboxylic acid is reacted with an alcohol in the presence of a hydrolyzable catalyst in an aqueous medium under mixing to produce a reaction mixture comprising an organic phase containing ester and an aqueous phase.
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Page/Page column 5
(2008/06/13)
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