Optical resolution of racemic 2-hydroxy octanoic acid using biphasic enzyme membrane reactor

A lipase-immobilized biphasic membrane reactor was applied for the optical resolution of racemic 2-hydroxy octanoic acid. Lipase from Candida rugosa or Pseudomonas cepacia was used as a biocatalyst, and three kinds of capillary membranes were employed as immobilization supports. The (S)-isomer of racemic 2-hydroxy octanoic acid methyl and butyl esters was preferentially hydrolyzed by both lipases. Immobilized P. cepacia lipase showed higher enantio-selectivity in biphasic membrane reactor than the native one did in emulsion stirred tank reactor, while immobilized C. rugosa lipase showed smaller enantio-selectivity than the native one. The use of butyl ester instead of methyl ester led to higher enantio-selectivity in C. rugosa lipase immobilized membrane reactor. In the membrane reactors with P. cepacia lipase immobilized, reaction rate and enantio-selectivity were affected by the types of membranes employed and the amount of enzyme loaded on the membrane. By use of biphasic membrane reactor with P. cepacia lipase immobilized, (R)-isomer and (S)-isomer of 2-hydroxy octanoic acid were obtained at the optical purity of 0.95 and 0.99 respectively.

In the enzymatic hydrolysis of racemic 2hydroxy octanoic acid esters, immobilized C. rugosa lipase showed lower enantio-selectivity in a biphasic membrane reactor than the native one did in an emulsion stirred tank reactor. On the other hand, the enantio-selectivity of immobilized P. cepacia l ipase in a biphasic membrane reactor was higher than that of the native one except the case of hydrolysis of the butyl ester in PES-membrane employed reactor. Three kinds of ultrafiltration capillary membranes were employed as supports of lipase in a biphasic membrane reactor, and the PES membrane gave the highest reaction rate per unit membrane area.