Enhanced Organic-Phase Enzymatic Esterification with Continuous Water Removal in a Controlled Air-Bleed Evacuated-Headspace Reactor

Abstract

The yield of organic-phase enzymatic esterification reactions can be improved by continuous removal of product water. When water is the only volatile component of the reaction system, this can be accomplished by carrying out the reaction under a partial vacuum. The performance in such reaction systems can be further improved by employing a controlled leak of air into the headspace of the reactor. This improvement is achieved at a lower vacuum than would be required in an ideal evacuated reactor delivering the same performance. The theory of air-leak effects has been analyzed in this paper. Experiments done to verify this theory have also been presented. Air-bleed evacuated-headspace reactors (ABEHRs) can produce extremely high synthetic yields. For instance, during the lipozyme-catalyzed esterification of a solvent-free solketal-decanoic acid mixture, a yield of 96% ester was obtained in a reactor operated under a vacuum of 0.7 bar and a temperature of 50°C when air at 20°C with a relative humidity of 54% was leaked into the headspace.

A water activity control system for enzymatic reactions in organic media

“…Some of the methods discussed in the Introduction section, for example equilibration with saturated salt solutions and addition of salt hydrate pairs are not feasible in large-scale processes due to slow mass transfer in the case of saturated salt solutions and impurities as well as regeneration problems in the case of salt hydrate pairs, respectively. Vacuum evaporation is an excellent method concerning water removal and combined with an air-bleed, water activity can be controlled (Napier et al, 1996). However, this method appears more complex while vacuum as well as water activity control of the leaking air are needed.…”

“…When the measurement of water activity has been solved, the next problem arises, namely, how to control it. Water removal has been studied by several researches and several ways have been suggested, for instance, vacuum evaporation (Napier et al, 1996), pervaporation (Gubicza et al, 2003;Kwon et al, 1995), absorption by cation-exchange resins (Meissner and Carta, 2002;Mensah et al, 1998), molecular sieves (Bloomer et al, 1992;Teo and Ruthven, 1986), etc. While these methods easily can be used for water removal, their use for adjusting the water activity to a specified level by adding and/or removing water is not so straightforward.…”

Computer‐Aided Control of Water Activity for Lipase‐Catalyzed Esterification in Solvent‐Free Systems

“…Several dehydration methods have been suggested in the literature. These include free evaporation (Selmi et al, 1997), vacuum evacuation (Napier et al, 1996), pervaporation (Kwon et al, 1995), dry gas bubbling (Kosugi and Azuma, 1994), and the use of selective adsorbents such as silica gel (Goldberg et al, 1988;Lee, 1996a, 1996b) and molecular sieves (Ergan et al, 1990).…”

Regioselective lipase-catalyzed synthesis of glucose ester on a preparative scale

“…Membrane pervaporation separation techniques have been developed recently because of their high separation efficiency and flux rates coupled with potential savings in energy costs [24][25][26]. These techniques depend on the fact that certain membranes permit easier passage of one liquid than of the other, thus changing the composition of the mixture [27].…”