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Feed batch addition of saccharide during saccharide‐fatty acid esterification catalyzed by immobilized lipase: Time course, water activity, and kinetic model
Author(s) -
Dang Hung T.,
Obiri Oriana,
Hayes Douglas G.
Publication year - 2005
Publication title -
journal of the american oil chemists' society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.512
H-Index - 117
eISSN - 1558-9331
pISSN - 0003-021X
DOI - 10.1007/s11746-005-1098-x
Subject(s) - chemistry , lipase , oleic acid , solubility , fructose , chromatography , catalysis , solvent , water activity , miscibility , nuclear chemistry , organic chemistry , water content , enzyme , biochemistry , geotechnical engineering , engineering , polymer
A conversion of 80–93% was achieved for esterification of oleic acid and fructose (or sucrose) catalyzed by immobilized Rhizomucor miehei lipase (Lipozyme IM; Novozymes, Franklinton, NC) at 65°C using near‐stoichiometric amounts of substrates. The product consisted of mono‐ and diester at a ratio of 9∶1 gg −1 . The main obstacle for achieving a high rate of reaction, the poor miscibility of the substrates, was overcome by taking advantage of the greatly increased solubility of fructose as the proportion of ester increased. A phase diagram demonstrated that the solubility of fructose increased linearly from 0.002 to 0.07 to 0.13 gg −1 as the ester mass fraction increased from 0.00 to 0.47 to 0.80, respectively. Solvent ( tert ‐butanol) was present only during the first phase of the time course of the reaction to enhance fructose solubility and was allowed to evaporate away completely on reaching 25% conversion. A conversion higher than 80–93% could not be achieved by reducing the bioreactor's water content through use of vacuum pressure or water activity control. Water adsorption isotherms demonstrate the significant increase of equilibrium liquid phase water content as the reaction progressed, which was due to higher water adsorption by the monoester relative to oleic acid. Increased removal of liquid phase water may result in the loss of water from the lipase, resulting in a reduction of its biocatalytic activity. Initial rate experiments were used to derive a Ping‐Pong Bi Bi kinetic model that strongly agreed with measured data for the time course of the reaction. Lipozyme IM did not lose activity when employed for three successive fructose‐oleate esterification batch reactions or, equivalently, for a 24‐d reaction period.