Electrically immobilized enzyme reactors: bioconversion of a charged substrate. Hydrolysis Of penicillin G by penicillin G acylase

Membrane-assisted extractive bioconversions

This chapter summarizes the use of membrane reactors in extractive bioconversions as process integration systems leading to in situ product recovery. Several membrane reactor configurations are analyzed, taking into account the type of bioconversion, biocatalyst type and location (either in the aqueous phase or in the membrane), membrane chemistry and morphology, solvent (extractant) type and its biocompatibility. Modeling of liquid-liquid extractive membrane bioreactors operation is also analyzed considering kinetics and mass-transfer aspects. The chapter includes examples from the authors' laboratory as well as other published in the field. Both enzyme and whole cell-based bioconversions are considered. Relevant aspects related to the solvent (extractant) toxicity and how the membrane could protect the biocatalytic activity are analyzed. Trends in this field are also given.

Separation of proteins in a multicompartment electrolyzer with chambers defined by a bed of gel beads

Multicompartment electrolyzers (MEs) with isoelectric membranes were introduced in 1989 for purifying proteins in an electric field. At the basis of ME technology there are membranes consisting of cross-linked copolymers of acrylamide and acrylamido monomers bearing protolytic groups. The technology employed for casting the membranes is an extension of the isoelectric focusing in immobilized pH gradient technique for which specific acrylamido monomers, known with the trade name of Immobiline, have been developed. However, the use of continuous membranes presents several disadvantages. Due to the mechanical characteristics of polyacrylamide, the gel must physically adhere onto a rigid support, which prevents it from collapsing. The support must have a highly porous structure in order to be permeable to proteins. The mechanical fragility of the membranes is one of the main problems that hinders the industrial scale application of ME separators. In order to overcome this problem, we propose to substitute the continuous membranes with a bed of gel beads of identical comonomer composition, obtained by an inverse emulsion polymerization process.

Stereoselective synthesis of (S)-(+)-Naproxen catalyzed by carboxyl esterase in a multicompartment electrolyzer

The stereoselective hydrolysis of racemic 2-substituted propionates, catalyzed by carboxyl esterase, provides a cost-competitive route to produce the optically pure, anti-inflammatory drug Naproxen. In the present work, we describe the application of the multicompartment electrolyzer reactor (ME) for the stereoselective hydrolysis of a racemic Naproxen ester, (R,S)-ethoxyethyl-[2-(6-methoxy-2-naphtyl)]propionate, catalyzed by a carboxyl esterase. The enzyme was trapped in a reactor chamber, delimited by two isoelectric membranes encompassing the pI value of the enzyme, together with the neutral substrate. After 90 min, a conversion of 45% was obtained with an enantiomeric excess of 84%. The reaction product, (S)-(+)-Naproxen, was electrophoretically removed in continuous from the reaction chamber and collected in a contiguous, more acidic chamber, separated from the enzyme and from the unreacted substrate. Moreover, at the end of the reaction, it was possible to recover the enzyme from the reactor and use it again.