Surfactant‐induced breakthrough effects during the operation of two‐phase biocatalytic membrane reactors

Abstract

Surface-active components, both reactants and products, are frequently encountered in two-phase, aqueous-organic, biocatalytic reactions, When such reaction are carried out in a membrane reactor, employing a membrane selectively wetted by one of the two reactants, changes in the content of these surfactants--as a consequence of the progress of the reaction--can lead to wetting transitions at the two membrane-liquid interfaces as a result of adsorption of the tenside. This can lead to a decrease in the pressure required to cause the, initially, nonwetting phase to break through the membrane. Such effects render difficult the operation of two-phase membrane bioreactors. Hence, it is necessary to make a careful selection of the membrane material and type by considering factors such as UF versus MF and low MWCO versus high MWCO to enable the reactor to be operated without breakthrough, but without significantly compromising the reaction rates that can be maintained.The phenomena leading to breakthrough effects are discussed in this paper, and experimental results for the hydrolysis of ethyl laurate by lipase from Candida rugosa in a batch flat sheet membrane reactor are presented with the reactor operated with a variety of membranes. An experimental result showing the decrease in the pressure required to cause breakthrough of the organic phase (for the system ethyl laurate-lauric acid-water) as the content of the highly surface-active lauric acid in the organic phase is increased is also presented for an asymmetric, hydrophilic meta-aramid ultrafiltration membrane.

A membrane bioreactor for biotransformations of hydrophobic molecules using organic solvent nanofiltration (OSN) membranes☆

“…In microporous MBBs, the breakthrough pressure is dramatically decreased by the presence of surfactants in the biomedium which reduces the surface tension between the two liquid phases [4][5][6]11,12]. Han et al reported a 30 bar breakthrough pressure in MPF 50, an OSN composite membrane [34], which is very much above the maximum pressure attainable in our system (0.4 bar).…”

“…To prevent phase breakthrough during microporous MBB operation, the transmembrane pressure must be strictly controlled in the 100 mbar range, which is very difficult to achieve in actual membrane contactors [4,11,13]. Pronk et al [5] reported the use of a Cuprophan hollow fiber membrane with an immobilized enzymatic system.…”

“…These can cause a considerable reduction in the membrane breakthrough pressure, which leads to aqueous-organic phase breakthrough and mixing of the two phases [4,5,11]. A mechanism for this phenomenon was outlined by Shroen et al [12] and Vaidya et al [11]: they found that the decrease in the interfacial surface tension and breakthrough pressure is caused by surface active compounds, primarily proteins, that adsorb progressively onto the membrane pore walls, thus changing the wettability of the membrane. This protein adsorption ultimately leads to phase breakthrough and emulsion formation.…”

Bioprocess Engineering for Microbial Synthesis and Conversion of Isoprenoids

“…A crucial point in process operation of microporous membranes is the careful control of the transmembrane pressure to avoid phase breakthrough, which leads to mixing of the two phases and to the same emulsification problems experienced in direct contact systems [29]. Surface-active components of the aqueous phase such as biosurfactants, proteins, or the cells themselves can cause a considerable reduction in the membrane breakthrough pressure [95]. However, in the case of kinetic resolution of racemic menthyl acetate the cells were placed on the same side of the membrane as the organic phase, pure racemic menthyl acetate, and the aqueous phase removed acetate from the vicinity of the cells.…”

06/02425 Aqueous-organic phases separation by membrane reactors in biodesulfurization reactions

“…This incongruence may be justified by the addition of the tensoactive agent to the emulsion used for rupture pressure assays. According to research by Vaidya et al, (1994), the presence of bio-surfactants causes a transition in the membranes moisturizing ability. This phenomenon lowers the pressure required to force through the non-permeating phase, thus indicating that the membrane fractures at a lower pressure than if it had not been exposed to the tensoactive agent.…”