INVESTIGADORES
FORESTI Maria Laura
artículos
Título:
Multiple effects of water content on solvent-free enzymatic esterifications
Autor/es:
M.L. FORESTI; M.N. PEDERNERA; V. BUCALÁ; M.L. FERREIRA
Revista:
ENZYME AND MICROBIAL TECHNOLOGY
Editorial:
Elsevier
Referencias:
Lugar: Shannon, Ireland; Año: 2007 vol. 41 p. 62 - 70
ISSN:
0141-0229
Resumen:
Enhancement of the catalytic activity of lipases has commonly been performed by biocatalyst
modification (immobilization on hydrophobic supports, activation with interfaces, pretreatment with
amphiphiles, etc.). In this work, the enhancement of the reaction rates obtained in lipase-catalyzed
esterifications is achieved through modification of the number of liquid phases present in the medium in
which the reaction takes place. The liquid medium may be constituted by either just one liquid phase or two
liquid phases. The split of the liquid phase can be controlled by manipulating the water initially added to the
system.
As a result of the study of the role of water on the solvent-free enzymatic esterification of oleic acid with
ethanol, the addition of relatively high amounts of water showed an unexpected beneficial effect: ester yields
increased in systems with high amounts of water initially added. The addition of high amounts of water to the
mixture of substrates led to the generation of two-liquid phases systems, in which the fatty acid and the
produced ester remained in the organic phase, the added and reaction-generated water migrated to the
aqueous phase, and the ethanol partitioned between both phases. The existence of a second aqueous
phase from the beginning of the reaction favored the extraction of the water generated in the reaction, with
an important reduction of the water content in the organic reactive phase. As a consequence, the increase in
the global water content of the reaction medium not only did not favor hydrolysis, but also increased the fatty
acid conversion in the first hours of reaction. Together with the lipase hydration and equilibrium shift, effects
commonly considered in the literature of lipase-catalyzed esterifications, this manuscript emphasizes
another effect of water related to the formation of a two-liquid phases system. Experimental and modeling
data from reactions catalyzed with up to 15 biocatalysts (native and immobilized lipases) are presented to
analyze the role of water on the rate of solvent-free enzymatic esterifications.